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Medullary projections to the vagus nerve and posterolateral hypothalamus.

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THE ANATOMICAL RECORD 242:251-258 (1995)
Medullary Projections to the Vagus Nerve and
Posterolateral Hypot ha1amus
S.G. PATRICK HARDY
Departments of Physical Therapy and Anatomy, The University of Mississippi Medical
Center, Jackson, Mississippi
ABSTRACT
Background: Vagal visceromotor reflexes are dependent
upon reciprocal neural connections existing between the medulla and the
hypothalamus. Medullohypothalamic neurons may provide feedback cues
to the hypothalamus regarding the activity of vagal motor neurons. As yet,
however, studies investigating the spatial relationships between medullohypothalamic neurons and vagal motor neurons have not been performed.
Methods: A variety of retrogradely transported tracers were used for the
purpose of mapping the relative locations of medullovagal and medullohypothalamic neurons. Tracers were injected into the cervical vagus nerve
and/or the posterolateral hypothalamus, and subsequently the retrogradely labeled medullary neurons were plotted.
Results: Labeling of the two neuronal populations was primarily observed within the ventrolateral and dorsomedial medulla. Within the ventrolateral medulla, medullovagal neurons were found within the retrofacial
nucleus and nucleus retroambiguus, whereas medullohypothalamic neurons were located subjacent to these nuclei. Within the dorsomedial medulla, labeling of the two neuronal populations was primarily limited to the
vagal-solitary complex. At this location medullovagal neurons were found
within the dorsal vagal nucleus, whereas medullohypothalamic neurons
were largely confined to the caudal aspect of the solitary nucleus.
Conclusions: Because of the spatial proximity existing between medullovagal and medullohypothalamic neurons, it is suggested that functional
interrelationships may exist between these two neuronal populations. Specifically, it is suggested that the medullohypothalamic neurons identified in
this study may support vagal-related functions by providing feedback cues
to the posterolateral hypothalamus. o 1995 Wiley-Liss, Inc.
Key words: Nucleus ambiguus, Vagal-solitary complex, Cardiovascular,
Respiratory, Fluorescent tracers, Horseradish peroxidase
The vagus nerve consists primarily of the processes
from general visceral efferent neurons (preganglionic
parasympathetic) and general visceral afferent neurons. These efferent and afferent fibers, each playing a
crucial role in the mediation of vagal reflexes, are connected to the medulla.
Vagal general visceral efferent fibers originate from
the dorsal vagal nucleus and nucleus retroambiguus
(the latter nucleus being referred t o by some (Bieger
and Hopkins, 1987) as the external formation of the
nucleus ambiguus). Axons from these medullary nuclei
traverse the vagus nerves and convey visceral motor
influences to a wide variety of thoracic and abdominal
viscera (Nosaka et al., 1979; Kalia and Mesulam, 1980;
Leslie et al., 1982; Bieger and Hopkins, 1987; NunezAbades et al., 1991). Importantly, these vagal motor
functions are themselves subject to hypothalamic influences which travel upon diffuse hypothalamomedullary pathways coursing through the lateral tegmentum of the brainstem (Saper et al., 1976; van der Kooy
0 1995 WILEY-LISS. INC.
et al., 1984).It has been reported that these descending
hypothalamomedullary projections are capable of altering vagal outputs to a variety of viscera, including
the stomach (Hara et all, 1990; Namiki et al., 1993; Ma
et al., 1994), heart (Cechetto and Chen, 1992), kidneys
(Schramm et al., 1993), thyroid/parathyroid glands
(Ma et al., 19941, and pancreas (Loewy and Haxhiu,
1993).
Vagal general visceral afferent fibers convey information from physiological receptors which are housed
within numerous viscera. These receptors include, but
are not limited to, stretch receptors in hollow organs
and baroreceptors in the aortic arch. The vagal afferents, conducting the viscerosensory information, traverse the vagus nerve and subsequently terminate
upon neurons within the nucleus of the solitary tract
Received October 17, 1994; accepted January 10,1995.
252
S.G.P. HARDY
aseptic conditions. A variety of retrogradely transported tracers (fluorescent and nonfluorescent) were
used in the study of medullary neurons having projections to either the posterolateral hypothalamus or vagus nerve. Fluorescent tracers included Diamidinodihydrochloride Yellow (DY) (2% in water), Fast Blue
(FBI (2%in water), and Fluorogold (FG) (10%in water).
Furthermore, the nonf luorescent tracer, wheat germ
agglutinin-horseradish peroxidase (WGA-HRP)(2% in
water) was used periodically during this study. A single
tracer was used in each of 42 animals, whereas multiple
tracers were used in each of 10 animals. It should, furthermore, be noted that three of the tracers used in this
study, (i.e., FB, FG, and WGA-HRP)have been reported
(Skirboll et al., 1989; Zaborszky and Heimer, 1989)not
to be taken up by unbroken axons of passage.
Tracer placements made into the posterolateral hypothalamus (n = 30) were accomplished by pressure
injection, using either a 5 or 10 p1 Hamilton syringe
and a microdrive (David Kopf Instruments, Tujunga,
CA) to depress the syringe plunger. To facilitate a localized placement of each of the injectants, a nonbeveled syringe needle was used. Each injection was made
over an approximate 10 min period. An additional 5
min was allowed to elapse prior t o removing the needle
from the injection site, in order to limit the spread of
the injectant. A typical injection volume for the injectants FB, FG, or WGA-HRP was 0.03-0.09 pl,
whereas a typical injection volume for the more viscous
DY was 0.18-0.27 p1.
Tracer placements were made into the vagus nerve
(n = 32) using the following method. With the aid of a
surgical microscope, the lower cervical portion of the
vagus nerve trunk was exposed and gently separated
from its connective tissue sheath. The vagus nerve was
then severed a t a point immediately superior to the
clavicle and the proximal nerve stump inserted into a
short (3-5 mm) segment of polyethylene tubing (PE =
901, which had previously been heat sealed on one end
and partially filled with one of the tracers used in this
study. Leakage typically did not occur during this process. A drop of cyanoacrylate glue was then applied to
the tubing entrance, thereby encapsulating the vagal
nerve stump and tracer substance.
After survival periods of 3-5 days (for the fluorescent tracer cases) and 24 h (for the WGA-HRP tracer
cases), the rats were deeply anesthetized with an overdose of chloral hydrate and perfused transcardially
with heparinized, normal saline, followed by an aldehyde fixative. For the fluorescent tracer cases, a 2.5%
paraformaldehyde fixative was used; however, for the
WGA-HRP tracer cases, a 1% paraformaldehyde1.25% glutaraldehyde fixative was employed. The
brains and spinal cords were then removed, blocked,
immersed in a 10% sucrose-phosphate buffer solution,
and refrigerated for several days. Sections were cut on
a freezing microtome at 40 pm. Sections taken from
WGA-HRP tracer cases were reacted with tetramethMATERIALS AND METHODS
ylbenzidine (TMB) (Mesulam, 1978). Tissues taken
Experiments were conducted on 52 Sprague-Dawley from fluorescent tracer cases were divided into two adrats weighing 325-450 g. Prior to surgery each animal jacent series. All sections were mounted out of phoswas deeply anesthetized with chloral hydrate (400 mg/ phate buffer onto gelatinized slides. One of the tissue
kg). Supplemental doses of the anesthetic were admin- series was left unstained for fluorescence microscopy.
istered when the animals demonstrated corneal or with- The other series was counterstained with 1%neutral
drawal reflexes. All surgery was performed under red, as were the reacted sections from the WGA-HRP
(NTS). Some of the NTS neurons project to neurons in
the ventrolateral medulla (Granata et al., 1983; Ross et
al., 1985). Many of the neurons within both the NTS
(Ricardo and Koh, 1978; Ter Horst et al., 1989; Riche et
al., 1990) and ventrolateral medulla (Blessing et al.,
1982; Sawchenko and Swanson, 1982) subsequently
project their axons upward into the hypothalamus,
thus providing a potential source of feedback for hypothalamic influences upon visceromotor functions. Supporting this concept, it has been revealed in physiological studies that medullohypothalamic influences are
indeed essential for certain vagal reflexes involving
the cardiovascular (Nissen et al., 1993) and gastrointestinal systems (Bray, 1985).
Considering the functional interrelationships existing between the vagus nerves and the hypothalamus, it
is important to better understand the anatomical bases
for those relationships. As yet, however, there are
many unanswered questions regarding the neuronal
circuitry which would be necessary to support vagalhypothalamic interactions. For example, because most
studies involving medullohypothalamic neurons have
focused upon those medullary inputs to supraoptic and
paraventricular nuclei, relatively little is known regarding medullary input to other hypothalamic areas.
Another issue in need of clarification is whether
medullohypothalamic and medullovagal neurons originate from discrete neuronal groups or perhaps originate from a common pool of neurons. Data reported in
the present paper will shed light on these two areas.
The specific medullary outputs examined in the
present study were medullovagal neurons, that are
channeled through the inferior cervical portion of the
vagus nerve, and medullohypothalamic neurons, having projections to the posterolateral hypothalamus.
Considerable evidence indicates that the posterolatera1 hypothalamus is largely involved in the regulation
of certain cardiovascular functions. For example, it has
been observed that activation of the posterolateral hypothalamus produces hypotension and bradycardia
(Hinrichsen, 1988; Gelsema et al., 1989; Spencer et al.,
1989). Furthermore, it has been demonstrated that the
posterolateral hypothalamus mediates emotion-related
fluctuations in blood pressure (LeDoux et al., 1988), as
well as the cardiovascular effects of prefrontal cortical
stimulation (Cechetto et al., 1988; Hardy and Mack,
1990). Interestingly, it has been found that the influence of the posterolateral hypothalamus upon cardiovascular functions is mediated over descending hypothalamomedullary pathways (Cechetto and Chen,
1992). Because the posterolateral hypothalamus is so
clearly involved in the regulation of cardiovascular activities, it is concluded that medullary neurons which
project to the posterolateral hypothalamus may play a
role in cardiovascular functions. A preliminary report
of these data has been published elsewhere (Hardy,
1992).
253
MEDULOVAGAL AND MEDULLOHYPOTHALAMIC NEURONS
tracer cases. All slides were then coverslipped with
D.P.X. mountant.
The sections were studied with a Zeiss Photomicroscope 111.An excitation wavelength of 360 nm was used
for the purpose of visualizing the fluorescent labeling.
The distributions of retrogradely labeled neurons
within the medulla were charted with an X-Y plotter
(Houston Instruments, Austin, TX) driven by linear
potentiometers on the microscope stage. The plots of
labeled neurons were transferred to drawings of the
adjacent neutral red-stained sections.
RESULTS
The four retrogradely transported tracers used in
this study were found to be highly discriminable because of their different hues and their different cytological labeling properties. Consequently, the distributions of the two populations of medullary neurons
focused upon in this study were easily distinguished.
Medullohypothalarnic Neurons
Medullohypothalamic neurons were labeled following solitary tracer (DY, FB, FG, or WGA-HRP) placements made into the posterolateral hypothalamus. Despite the fact that different tracers were used in this
study, the distribution of labeled medullohypothalamic
neurons was similar in each case. In every case the
tracer placements were made medial to the subthalamic nucleus and lateral to the fornix (see Fig. 1A).
Neurons having projections to the posterolateral hypothalamus were observed at a variety of locations
within the medulla. In the rostral medulla, moderate
numbers of medullohypothalamic neurons were observed ventromedially, within the nucleus raphe magnus, nucleus reticularis magnocellularis, and rostral
ventrolateral medulla (Fig. 1B-D). In the caudal medulla, neurons having projections to the posterolateral
AP
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DC
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G
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LRm
2
MTT
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NA
NTS
OT
P
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ST
STT
SUT
VII
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X
XI1
A bbreuiations
area postrema
crus cerebri
lateral cuneate nucleus
medial cuneate nucleus
dorsal cochlear nucleus
fornix
fasciculus retroflexus
gracile nucleus
habenula
inferior cerebellar peduncle
inferior olivary nucleus
lateral reticular nucleus, pars magnocellularis
lateral reticular nucleus, pars parvocellularis
medial lemniscus
mammillothalamic tract
medial vestibular nucleus
nucleus retroambiguus/external formation of the nucleus ambiguus
nucleus of the solitary tract
optic tract
medullary pyramid
prepositus hypoglossi nucleus
retrofacial nucleus
spinal trigeminal nucleus
spinal trigeminal tract
subthalamic nucleus
facial motor nucleus
vestibulospinal nucleus
dorsal vagal nucleus
hypoglossal nucleus
hypothalamus were abundant within the ipsilateral
nucleus of the solitary tract (Figs. 1F-G, ZB). In addition, numerous medullohypothalamic neurons were observed bilaterallv. within the reticular formation lvinp
immediately sugjacent to the nucleus retroambiguus
(Figs. 1E,F, ZD, 3).
.
I
"
Medullovagal Neurons
Neurons retrogradely labeled by tracers applied to
the vagus nerve were also observed in both the rostral
and caudal medulla. In the rostral medulla, medullovagal neurons were found within and ventral to the ipsilateral retrofacial nucleus (Fig. 1B-D). In the caudal
medulla, neurons having projections into the vagus
nerve were observed ipsilaterally in both the dorsal
vagal nucleus and in the dorsomedial aspect of the nucleus retroambiguus (Figs. 1E-G, ZC, 3).
Spatial Relationships Revealed by Multiple Injections
By using multiple retrograde tracers, it was possible
to observe directly the spatial relationships existing
between the two neuronal populations being studied.
Data from these experiments served t o confirm the results of the single injectant experiments. Furthermore,
the use of multiple injectants made it possible to better
recognize those areas in which the two populations of
medullary efferents were coextensive. For these purposes, a series of experiments was performed in which
two injectants were administered into each animal.
Data resulting from these experiments confirmed the
locations of medullohypothalamic and medullovagal
neurons, as described above. Although double-labeled
neurons were never observed, the resulting data also
made it possible to observe the spatial interrelationships existing among the two neuronal populations
(Figs. 1-3). Furthermore, those areas containing both
types of medullary efferents were easily recognized.
Examples of distributional overlap (or juxtaposition)
were observed in the ventrolateral and dorsomedial
medulla. These areas are described below and illustrated in Figure 1.
In the ventrolateral medulla, the two populations of
neurons were primarily observed in the vicinity of the
nucleus retroambiguus (NA) and, to a more limited
extent, in the vicinity of the caudal portion of the retrofacial nucleus. In the vicinity of the NA (Figs. ZC, 31,
medullovagal projections were observed to originate
primarily from the dorsomedial aspect of NA. Medullohypothalamic projections did not originate from the
NA but rather from an area immediately ventral to it
(Figs. ZD, 3) In the vicinity of the retrofacial nucleus
(Fig. 10, medullovagal projections were observed to
originate from the retrofacial nucleus, as well as from
the subjacent reticular formation. In addition to
medullovagal neurons, the subretrofacial region was
also observed to contain medullohypothalamic neurons
(Fig. lC,D).
In the dorsomedial medulla, the two neuronal populations were primarily observed in the caudal portion
of the vagal-solitary complex (Figs. 1F,G, ZB). At this
location, numerous medullovagal neurons were observed to originate from the dorsal vagal nucleus. Dorsally contiguous with these medullovagal neurons, and
residing within the medial portion of the nucleus of the
solitary tract, were medullohypothalamic neurons.
254
S.G.P. HARDY
CL
LRm
ICP
LRm
*-HYPOTHALAMUS
0 -VAGUS
HYPO-41
Fig. 1. Illustration of retrogradely labeled medullohypothalamic (stars) and medullovagal (dots) neurons from rostra1 (B) to caudal (G)levels of the medulla following a microinjection (0.27 kl) of Diamidinodihydrochloride Yellow (DY)into the posterolateral hypothalamus (A) and the immersion of the vagus
nerve in Fluorogold of a single animal (Hypo-41).
DISCUSSION
In the present study, the relative locations of medullohypothalamic and medullovagal neurons are de-
scribed. The medullohypothalamic neurons that are described in this study are those having projections to the
posterolateral hypothalamus, an area well known for
MEDULOVAGALANDMEDULLOHYPOTHALAMICNEURONS
255
Fig. 2. A composite of photomicrographs taken of medullovagal
and/or medullohypothalamic neurons located within the caudal portion of the vagal-solitary complex (A,B) and within the vicinity of the
nucleus retroambiguus (C,D). A Brightfield photomicrograph of the
caudal aspect of the dorsomedial medulla. The tissue has been stained
with neutral red in order to reveal the regional cytoarchitecture. The
rectangle encompasses most of the nucleus of the solitary tract (NTS)
and the dorsal motor nucleus of the vagus nerve (XI. B: Fluorescent
photomicrograph of retrogradely labeled neurons, corresponding in
location to the rectangle of A but photographed in an adjacent, unstained section. A t the top of the photomicrograph, located within the
nucleus of the solitary tract, are Fluorogold-labeled medullohypothalamic neurons. At the bottom of the photomicrograph, located within
the dorsal motor nucleus of the vagus nerve, are medullovagal neurons which have been labeled following the immersion of the vagus
nerve in Diamidino-dihydrochlorideYellow. C: Fluorescent photomicrograph of Fluorogold-labeled medullovagal neurons. The tissue has
been stained with neutral red, thus making it possible to observe that
the medullovagal neurons are located in the dorsal aspect of the nucleus retroambiguus (NA). D Brightfield photomicrograph of WGAHRP-labeled medullohypothalamic neurons. Note that the labeled
neurons are subjacent to the nucleus retroambiguus (NA).
its involvement in cardiovascular activities (Cechetto
et al., 1988; Hinrichsen, 1988; LeDoux et al., 1988;
Gelsema et al., 1989; Spencer et al., 1989; Hardy and
Mack, 1990). Consequently, the medullohypothalamic
neurons which are identified in this study are likely to
play a role in cardiovascular functions. Conversely, it
is somewhat more difficult to link the medullovagal
neurons, retrogradely labeled in this study, with a particular function. This is largely due to the fact that the
vagus nerve is involved in a variety of functions, most
of which are dedicated to the control of one’s internal
environment.
Medullohypothalamic neurons, as observed in this
study, were distributed in a manner which varied only
slightly from previous reports (Ricardo and Koh, 1978;
Blessing et al., 1982; Sawchenko and Swanson, 1982;
Ter Horst et al., 1989;Riche et al., 1990). Interestingly,
none of these previous studies were designed to comprehensively identify medullohypothalamic inputs
which were specific to the posterolateral portion of the
hypothalamus. Instead, some of these studies were intended to identify various medullary neurons which
projected to the paraventricular (Blessing et al., 1982;
Sawchenko and Swanson, 1982) and supraoptic nuclei
(Sawchenko and Swanson, 1982), while other studies
were designed to reveal projections from the nucleus of
the solitary tract (NTS) to the hypothalamus in general
(Ricardo and Koh, 1978; Ter Horst et al., 1989; Riche et
al., 1990). Nevertheless, the findings of these earlier
studies tend to be in agreement with the findings of the
present study. For example, previous studies indicated
that NTS-hypothalamic projections originated from the
caudal and medial portions of the NTS (Ricardo and
Koh, 1978; Ter Horst et al., 1989; Riche et al., 1990)
and that some of these projections terminated within
the posterolateral portion of the hypothalamus
(Ricardo and Koh, 1978).Both of these observations are
consistent with the findings of the present study.
256
S.G.P. HARDY
Fig. 3. Fluorescent photomicrographs of retrogradely labeled neurons within and ventral to the nucleus retroambiguus (NA). A The
perimeter of the NA is indicated by the dotted line. Medial is to the
right, and dorsal is at the top. Fluorogold-labeled medullovagal neurons (arrows) are primarily located in the dorsomedial NA. Subjacent
to the NA are medullohypothalamic neurons (closed arrowheads)
which were retrogradely labeled following a microinjection of Diami-
dino-dihydrochloride Yellow made into the posterolateral hypothalamus. (Open arrowheads indicate the presence of medullospinal neurons within the ventral NA. These medullospinal neurons are the
focus of another study, and the data regarding these neurons have
been excluded from the present study.) B Higher magnification of the
medullohypothalamic neurons, as seen within the square of A. Closed
arrowheads, medullohypothalamic neurons.
It has been demonstrated (Sawchenko and Swanson,
1982; Blessing et al., 1982) that the paraventricular
nucleus receives input from the NTS and the ventrolateral medulla. The fact that neurons in these areas
also project to the posterolateral hypothalamus, as
demonstrated in the present study, suggests that these
neurons may be able to concomitantly influence both
the paraventricular nucleus and the posterolateral hypothalamus. Interestingly, it has been well documented that each of these hypothalamic sites plays
important roles in cardiovascular regulation. The similarity of medullohypothalamic inputs into these two
hypothalamic sites may contribute to their functional
similarities. Conversely, in previous studies (Blessing
et al., 1982; Sawchenko and Swanson, 1982), neurons
in the ventromedial and paraolivary regions were not
observed to project to the paraventricular nucleus,
whereas in the present study a modest number of neu-
rons, originating from these regions of the rostra1 medulla, were observed to project to the posterolateral
hypothalamus (Fig. 1B-D). Thus medullohypothalamic inputs originating from the ventromedial and
paraolivary regions may be more exclusively related to
the posterolateral hypothalamus than those originating from the ventrolateral medulla and nucleus of the
solitary tract.
Medullovagal neurons, as observed in this study,
were distributed in a manner similar to that described
in earlier reports (Leslie et al., 1982; Bieger and Hopkins, 1987). Accordingly, medullovagal neurons were
typically observed within: the dorsal vagal nucleus, the
retrofacial nucleus, and the nucleus retroambiguus.
Previous studies (Nosaka et al., 1979; Pagani et al.,
1983; Imaizumi et al., 1985; Bieger and Hopkins, 1987)
have indicated that vagal cardioinhibitory neurons are
primarily located within the dorsal vagal nucleus and
MEDULOVAGALANDMEDULLOHYPOTHALAMICNEURONS
within the nucleus retroambiguus. Conversely, medullovagal neurons located within the retrofacial nucleus
primarily innervate the esophagus (Bieger and Hopkins, 1987).
From the multiple tracer experiments, it was observed that medullohypothalamic and medullovagal
neurons were in close proximity within the ventrolatera1 and dorsomedial regions of the caudal medulla,
where they resided within the caudal portion of the
vagal-solitary complex and within the vicinity of the
nucleus retroambiguus. Interestingly, and as previously noted, these areas are known to contain cardioinhibitory neurons (Nosaka et al., 1979; Pagani et al.,
1983;Imaizumi et al., 1985; Bieger and Hopkins, 1987).
In the caudal portion of the vagal-solitary complex,
medullohypothalamic neurons were observed within
the nucleus of the solitary tract, whereas medullovagal
neurons occupied an immediately subjacent location,
within the dorsal vagal nucleus. In the caudal portion
of the ventrolateral medulla, medullovagal neurons
were present within the nucleus retroambiguus. Medullovagal neurons were typically located in the dorsomedial aspect of this nucleus. This observation is in
agreement with the findings of previous studies (Nunez-Abades et al., 1991, 1992). Medullohypothalamic
neurons were located immediately subjacent to the nucleus retroambiguus but were not observed within the
nucleus itself. This latter finding is consistent with the
previous observations of others (Blessing et al., 1982;
Sawchenko and Swanson, 1982).
As revealed in this study, it seems apparent that the
caudal portions of the dorsomedial and ventrolateral
medulla, because of their neuronal content, have the
potential to influence those functions associated with
the vagus nerve and the posterolateral hypothalamus.
It is suggested that some of the medullohypothalamic
neurons identified in this study, and particularly those
lying in close proximity to medullovagal neurons, may
provide feedback information to the hypothalamus regarding the extent to which the hypothalamus has influenced the activity of medullovagal neurons. Such a
system would be consistent with the viewpoint that
“corollary discharge” (Sperry, 1950), also known as “efference copy” (Holst and Mittelstaedt, 19501, is an organizational feature existing within all motor systems,
providing feedback to higher levels of the neuraxis regarding the motor output occurring at lower levels. In
support of this concept as it relates to vagal motor functions, it has been demonstrated that medullohypothalamic neurons are essential for the occurrence of certain vagal motor reflexes (Bray, 1985; Nissen et al.,
1993). It should also be noted that most of the medullohypothalamic neurons were located either within the
ventrolateral medulla or within the nucleus of the solitary tract. The fact that both of these areas receives
vagal afferent input (Granata et al., 1983; Ross et al.,
1985) provides additional support for the notion that
these medullohypothalamic neurons may provide feedback to the hypothalamus.
The anatomical data gathered in the present study
demonstrate the spatial interrelationships among
medullovagal and medullohypothalamic neurons. It is
anticipated that future studies will be directed toward
better understanding any functional interrelationships
existing among these neurons.
257
ACKNOWLEDGMENTS
The author thanks S.M. Mack for technical assistance during some of the experiments and Dr. P.J. May
and Dr. G.A. Mihailoff for reading the manuscript.
This study was supported in part by NIH grant 1-R15NS32861-01.
LITERATURE CITED
Bieger, D., and D.A. Hopkins 1987 Viscerotopic representation of the
upper alimentary tract in the medulla oblongata in the rat The
nucleus ambiguus. J . Comp. Neurol., 262.546462.
Blessing, W.W., C.B. Jaeger, D.A. Ruggiero, and D.J. Reis 1982 Hypothalamic projections of medullary catecholamine neurons in
the rabbit: A combined catecholamine fluorescence and HRP
transport study. Brain Res. Bull., 9:279-286.
Bray, G.A. 1985 Autonomic and endocrine factors in the regulation of
food intake. Brain Res. Bull., 14505-510.
Cechetto, D.F., and S.J. Chen 1992 Hypothalamic and cortical sympathetic responses relay in the medulla of the rat. Am. J . Physiol., 263:R544-552.
Cechetto, D.F., V.C. Hachinski, and S.J. Chen 1988 Efferent pathways for sympathetic responses from insular cortex. Neurosci.
Abstr., 14.616.
Gelsema, A.J., M.J. Roe, and F.R. Calaresu 1989 Neurally mediated
cardiovascular responses to stimulation of cell bodies in the hypothalamus of the rat. Brain Res., 482:67-77.
Granata, A.R., D.A. Ruggiero, D.H. Park, T.H. Joh, and D.J. Reis
1983 Lesions of epinephrine neurons in the rostra1 ventrolateral
medulla abolish the vasodepressor components of baroreflex and
cardiopulmonary reflex. Hypertension, 5:V80-84.
Hara, N., Y. Hara, Y. Natsume, and Y. Goto 1990 Direct evidence
indicating that a GABA-mimetic stimulates acid secretion
through central mechanisms. Jpn. J . Pharmacol., 53:271-274.
Hardy, S.G.P. 1992 Anatomical relationships among three populations of medullary efferents: Reticulohypothalamic, reticulovagal, and reticulospinal neurons. Neurosci. Abstr., 18:1186.
Hardy, S.G.P., and S.M. Mack 1990 Brainstem mediation of prefrontal
stimulus-produced hypotension. Exp. Brain Res., 70:393-399.
Hinrichsen, C.F.L. 1988 Projections of the midlateral posterior hypothalamic area influencing cardiorespiratory function in rats.
Brain Behav. Evol., 32t108-118.
Holst, E. von, and H. Mittelstaedt 1950 Das reafferenzprinzip.
Wechselwirkungen zwischen zentralnervensystem und peripherie. Naturwissenschaften, 37:463-476.
Imaizumi, T., A.R. Granata, E.E. Benarroeh, A.F. Sved, and D.J. Reis
1985 Contributions of arginine vasopressin and the sympathetic
nervous system to fulminating hypertension after destruction of
neurons of caudal ventrolateral medulla in the rat. J . Hypertens.,
3:491-501.
Kalia, M., and M.-M. Mesulam 1980 Brain stem projections of sensory
and motor components of the vagus complex in the cat: I. The
cervical vagus and nodose ganglion. J. Comp. Neurol., 193:435465.
LeDoux, J.E., J. Iwata, P. Cicchetti, and D.J. Reis 1988 Different
projections of the central amygdaloid nucleus mediate autonomic
and behavioral correlates of conditioned fear. J. Neurosci.,
8:2517-2529.
Leslie, R.A., D.G. Gwyn, and D.A. Hopkins 1982 The central distribution of the cervical vagus nerve and gastric afferent and efferent projections in the rat. Brain Res. Bull., 8:37-43.
Loewy, A.D., and M.A. Haxhiu 1993 CNS cell groups projecting to
pancreatic parasympathetic preganglionic neurons. Brain Res.,
620:323-330.
Ma, J., S. Aou, and T. Hori 1994 Hypothalamic stimulation induces
vagally mediated hypocalcemia in the rat. Brain Res. Bull., 33:
65-69.
Mesulam, M.-M. 1978 A tetramethylbenzidine method for the light
microscopic tracing of neural connections with horseradish peroxidase (HRP) neurohistochemistry. In: Neuroanatomical Techniques, Short Course. Society for Neuroscience, Bethesda, pp. 6571.
Namiki, T., M. Egawa, S. Tominaga, S. Inoue, and Y. Takamura 1993
Effects of GABA and L-glutamate on the gastric acid secretion
and gastric defensive mechanisms in rat lateral hypothalamus. J.
Auton. Nerv. Syst., 44r217-223.
Nissen, R., J.T. Cunningham, and L.P. Renaud 1993 Lateral hypothalamic lesions alter baroreceptor-evoked inhibition of rat supraoptic vasopressin neurones. J. Physiol. (Lond.), 470:751-766.
258
S.G.P. HARDY
Nosaka, S., T. Yamamoto, and K. Yasunaga 1979 Localization of vagal cardioinhibitory preganglionic neurons within rat brain stem.
J. Comp. Neurol., 186:79-92.
Nunez-Abades, P.A., R. Pasaro, and A.L. Bianchi 1991 Localization of
respiratory bulbospinal and propriobulbar neurons in the region
of the nucleus ambiguus of the rat. Brain Res., 568:165-172.
Nunez-Abades, P.A., R. Pasaro, and A.L. Bianchi 1992 Study of the
topographical distribution of different populations of motoneurons within rat’s nucleus ambiguus, by means of four different
fluorochromes. Neurosci. Lett., 135r103-107.
Pagani, F.D., W.P. Norman, D.K. Kasbekar, and R.A. Gillis 1983
Comparison of gastroduodenal and cardiovascular responses produced by electrical stimulation of the dorsal motor nucleus of the
vagus and nucleus ambiguus in the rat. Neurosci. Abstr., 9:114.
Ricardo, J.A., and E.T. Koh 1978 Anatomical evidence of direct projections from the nucleus of the solitary tract to the hypothalamus, amygdala, and other forebrain structures in the rat. Brain
Res., 153:l-26.
Riche, D., J . De Pommery, and D. Menetrey 1990 Neuropeptides and
catecholamines in efferent projections of the nuclei of the solitary
tract in the rat. J . Comp. Neurol., 293.399-424.
Ross, C.A., D.A. Ruggiero, and D.J. Reis 1985 Projections from the
nucleus tractus solitari to the rostra1 ventrolateral medulla. J .
Comp. Neurol., 242.511-534.
Saper, C.B., A.D. Loewy, L.W. Swanson, and W.M. Cowan 1976 Direct
hypothalamo-autonomic connections. Brain Res., 11 7:305-312.
Sawchenko, P.E., and L.W. Swanson 1982 The organization of noradrenergic pathways from the brainstem to the paraventricular and
supraoptic nuclei in the rat. Brain Res. Rev., 4:275-325.
Schramm, L.P., A.M. Strack, K.B. Platt, and A.D. Loewy 1993 Peripheral and central pathways regulating the kidney: A study
using pseudorabies virus. Brain Res., 616:251-262.
Skirboll, L.R, K. Thor, C. Helke, T. Hokfelt, B. Robertson, and R. Long
1989 Use of retrograde fluorescent tracers in combination with
immunohistochemical methods, In: Neuroanatomical Tract-Tracing Methods 2. L. Heimer and L. Zaborszky, eds. Plenum Press,
New York, pp. 5-18.
Spencer, S.E., W.B. Sawyer, and A.D. Loewy 1989 Cardiovascular
effects produced by L-glutamate stimulation of the lateral hypothalamic area. Am. J. Physiol., 257:H540-552.
Sperry, R.W. 1950 Neural basis of the spontaneous optokinetic response produced by visual inversion. J . Comp. Physiol. Psych.,
43:482-489.
Ter Horst, G.J., P. De Boer, P.G.M. Luiten, and J.D. Van Willigen
1989 Ascending projections from the solitary tract nucleus to the
hypothalamus. A phaseolus vulgaris lectin tracing study in the
rat. Neuroscience, 31:785-797.
van der Kooy, D., L.Y. Koda, J.F. McGinty, C.R. Gerfen, and F.E.
Bloom 1984 The organization of projections from the cortex,
amygdala, and hypothalamus to the nucleus of the solitary tract
in rat. J. Comp. Neurol., 224:l-24.
Zaborszky, L., and L. Heimer 1989 Combinations of tracer techniques,
especially HRP and PHA-L, with transmitter identification for
correlated light and electron microscopic studies. In: Neuroanatomical Tract-Tracing Methods 2. L. Heimer and L. Zaborszky,
eds. Plenum Press, New York, pp. 49-96.
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