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Electrophysiological and morphological characteristics of nucleus tractus solitarii neurons projecting to the ventrolateral medulla

October 2000
Brain Research 877(2):374-8

October 2000
877(2):374-8

DOI:10.1016/S0006-8993(00)02701-3

Source
PubMed

Authors:

Yoshinori Kawai

AIBS

Electrophysiological and morphological properties of a direct projection from the nucleus of the tractus solitarius (NTS) to the ventrolateral medulla (VLM) were investigated. NTS neurons projecting to the VLM exhibit a monosynaptic excitatory response followed by an inhibitory one after the tractus solitarius stimulation. These neurons show spontaneous inhibitory postsynaptic currents, and have medium to large soma (14-26 microm in diameter). It is concluded that the projection from the NTS to the VLM is mediated mostly by medium to large neurons that are inhibited locally by GABAergic interneurons within the NTS.

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Brain Research 877 (2000) 374–378 www.elsevier.com/locate / bres

Short communication

Electrophysiological and morphological characteristics of nucleus

tractus solitarii neurons projecting to the ventrolateral medulla

Yoshinori Kawai , Emiko Senba

Department of Anatomy and Neurobiology

Wakayama Medical College

, 811

Kimiidera

Wakayama

641

8509,

Japan

Accepted 11 July 2000

Abstract

Electrophysiological and morphological properties of a direct projection from the nucleus of the tractus solitarius (NTS) to the

ventrolateral medulla (VLM) were investigated. NTS neurons projecting to the VLM exhibit a monosynaptic excitatory response followed

by an inhibitory one after the tractus solitarius stimulation. These neurons show spontaneous inhibitory postsynaptic currents, and have

medium to large soma (14–26 mm in diameter). It is concluded that the projection from the NTS to the VLM is mediated mostly by

medium to large neurons that are inhibited locally by GABAergic interneurons within the NTS. 2000 Elsevier Science B.V. All rights

reserved.

Theme

Endocrine and autonomic regulation

Topic

Cardiovascular regulation

Keywords

GABA; Glutamate; Patch clamp; Chemoreceptor; Baroreceptor

The direct projections from the caudal/intermediate synaptic EPSP, an EPSP/IPSP response. Our previous

nucleus of the tractus solitarius (NTS) to the ventrolateral studies [9,10] have shown that the former type of neurons

medulla (VLM) are critical pathways mediating car- has a small cell body with extended axon collateral arbors

diovascular and respiratory reﬂexes involving baro- and within the NTS, while the latter type of cells has a medium

chemoreceptor responses [4,15]. These projections include to large cell soma with few axon collaterals. In order to

sympathoexcitatory pathway to the rostral VLM (RVLM) understand the way of local processing of the peripheral

conveying chemoreceptor activity, and baroreceptor sensi- information, we addressed to elucidate to which type of

tive pathway to the caudal VLM (CVLM). In addition, cells the NTS neurons projecting to the VLM belong,

more recent studies have shown a direct GABAergic employing patch-clamp whole-cell recordings combined

projection from the CVLM to the RVLM [2,12]. Some with intracellular staining with biocytin.

RVLM neurons thus exert convergent control to the Experiments were performed on male Sprague–Dawley

preganglionic sympathetic neurons of the intermediolateral rats (P16–28: 35–100 g) anesthetized deeply with

nucleus of the spinal cord, thus mediating tonic and reﬂex urethane. Conventional coronal slices of 500 mm thickness

adjustments of sympathetic ﬂow according to the peripher- were cut on a Vibratome. The single slices contained both

al environments [4,15]. The peripheral inputs are ﬁrst caudal/intermediate NTS and the CVLM. In some experi-

integrated in the caudal/intermediate NTS. Several studies ments, semi-coronal slices were prepared so that single

[5,6,9,11] have demonstrated NTS neurons exhibit at least slices contained both the NTS at the level of the area

two types of postsynaptic responses following stimulation postrema and the RVLM. The standard Ringer solution had

of the peripheral primary afferents; one involves only the following composition (in mM): 125 NaCl, 2.5 KCl, 2

excitatory postsynaptic potentials (EPSPs) and the other an CaCl , 1 MgCl , 1.25 NaH PO , 26 NaHCO , 10 glucose,

22 24 3

inhibitory postsynaptic potential (IPSP) following a mono- and was continuously bubbled with a mixed 95% O –5%

CO (pH 7.4). Blind patch-clamp whole-cell recordings

were performed. The electrodes contained (in mM): 140

*Corresponding author. Tel./fax: 181-73-441-0617.

E-mail address

ykawai@wakayama-med.ac.jp (Y. Kawai). K-gluconate, 0.1 CaCl , 2 MgCl , 1.0 EGTA, 2 ATP, 10

PII: S0006-8993(00)02701-3

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HEPES and 0.5% biocytin (Sigma) (pH 7.3). Isolated axons were usually reconstructed from several consecutive

single stimuli of 40–100 ms were applied through tungsten sections.

bipolar electrodes positioned on the VLM regions of the Forty-eight NTS neurons showed either an EPSP/IPSP

slices, and another stimulation electrode of the same type or EPSPs response orthodromically to stimulation of the

was positioned at the dorsomedial part of the tractus TS and were reconstructed by intracellular staining with

solitarius (TS). Antagonists (bicuculline methiodide, 10 biocytin. Total 22 cells exhibited an EPSP/IPSP response

mM: Sigma, 6-cyano-7-nitroquinoxaline-2,3-dione orthodromically to the TS stimulation (Fig. 1A3). Some of

[CNQX], 10 mM: Research Biochemicals Incorporated) these cells showed prominent spontaneous inhibitory post-

were dissolved in the Ringer solution and bath-applied. synaptic currents (IPSCs) at a holding potential of about

After recordings, the resectioned slices were incubated in 240 mV (Fig. 1A2). These inhibitory responses were

avidin–biotin–horseradish peroxidase complex (1:250, blocked reversibly by bicuculline (10 mM, Fig. 1A3).

Vector ABC kit) in 0.1 M phosphate-buffered saline Remaining 26 neurons showing only EPSPs following the

containing 0.03% Triton X-100, followed by diaminoben- TS stimulation (Fig. 1B2). Some of them exhibited

zidine tetrahydrochloride reaction with ammonium nickel prominent spontaneous EPSCs when the membrane po-

intensiﬁcation. The sections were air-dried and embedded tentials were held at about 240 mV (Fig. 1B1). These

in Permount. Neuronal processes including projection excitatory responses were completely blocked by CNQX

Fig. 1. Electrophysiological properties of NTS neurons projecting to the VLM. (A1) Antidromic spikes observed in one NTS neuron by stimulations (the

artifacts are indicated by asterisk) of the VLM. (A2) This neuron shows spontaneous outward currents at a holding potential of 240 mV. Consecutive ﬁve

sweeps of currents are superimposed. (A3) Primary afferent (tractus solitarius; TS) stimulations evoke an inhibitory postsynaptic response that was

reversibly blocked by bicuculline, following a monosynaptic excitatory postsynaptic potential (EPSP) in the same neuron. The membrane potential was

clamped at 242 mV. The resting membrane potential of this neuron was 261 mV. (B1) Another type of postsynaptic responses observed in other NTS

neurons. Spontaneous postsynaptic currents were inward at a holding potential of 240 mV. Consecutive ﬁve sweeps of currents are superimposed. (B2) In

these neurons the TS stimulations elicited polysynaptic excitatory responses following a monosynaptic EPSP.

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Fig. 2. Three examples (A–C) of projections from the NTS to the VLM. Contralateral projections are sometimes observed (A). Calibrations in A apply to

B and C. Asterisks indicate projection axons. (D) Axonal arborizations in the RVLM as indicated by a dotted square in C. ap, area postrema; CVLM,

caudal ventrolateral medulla; dmnX, dorsal motor nucleus of the vagus; RVLM, rostral ventrolateral medulla; TS, tractus solitarius.

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(10 mM) [10]. Some of the axons of these cells were the NTS [13,14]. These results suggest that the peripheral

observed to leave the boundary of the NTS, but none of inputs could be processed by distinct ways within the NTS

them reached the VLM [10]. Of 22 cells showing an and transmitted to speciﬁc brain regions via different

EPSP/IPSP response after TS stimulation, 13 neurons were groups of the NTS neurons in terms of morphological and

identiﬁed as the VLM-projection cells by the reconstruc- electrophysiological characteristics.

tion of their projection axons to the either CVLM (n58) or The present study also showed that the VLM-projecting

RVLM (n55). Some of these neurons (CVLM 6, RVLM NTS neurons receive tonic GABAergic synaptic inputs.

3) had given rise to spikes in response to stimulations of This seems to be reasonable considering their role as reﬂex

the VLM regions of the slices (Fig. 1A1). These action neurons conveying baro- and chemoreceptor peripheral

potentials were considered to be antidromic spikes, be- inputs to the CVLM and RVLM, respectively. Because

cause they were all or none and no subthreshold EPSPs these cells can produce spikes faithfully in response to the

were observed in these cells. The mean latency of the peripheral excitation, while they are silent in the absence

antidromic spikes of CVLM- and RVLM-projection cells of peripheral inputs. On the other hand, the other group of

were 10.363.4 ms (n54) and 16.462.3 ms (n53), respec- neurons were shown to receive tonic excitatory synaptic

tively. No differences in morphological and electrophysio- inputs, and their behaviors in response to the peripheral

logical properties were evident between the CVLM- and excitation are likely to be quite different from those of the

RVLM-projection neurons. The VLM-projection cells had VLM-projection neurons.

soma of 18.263.8 mm(n510) in mean diameter, and 2–5 In conclusion, the peripheral information including baro-

primary dendrites (Fig. 2). These cells were located in and chemoreception is likely to be processed in a highly

medial and dorsomedial subnuclei of the NTS (Fig. 2). The integrated manner in the NTS and medium to large

projection axons were observed to leave the NTS, travel neurons directly convey the peripheral excitation to the

ventrolaterally in the reticular formation and reach the VLM with local synaptic interactions by other types of

VLM regions, giving rise to a moderate number of axonal NTS neurons, especially GABAergic interneurons.

branchings and boutons. These axons project to the

ipsilateral VLM in most cases, however, in some cases

(n53) contralateral projection was observed. Limited References

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Single-unit recording experiments were done in chloralose-anesthetized, paralyzed and artificially ventilated cats to identify neurons in ventrolateral medulla (VLM) that send efferent axons directly to the region of the nucleus of the solitary tract (NTS) and receive cardiovascular afferent inputs from the carotid sinus (CSN) and aortic depressor (ADN) nerves and the NTS. Units in VLM were identified by antidromic excitation to stimulation of functionally and histologically verified sites in the NTS complex. Antidromic potentials were recorded from 34 units in VLM. Units responded with a mean antidromic latency of4.37 ± 0.32 ms corresponding to a mean conduction velocity of0.93 ± 0.07m/s. Of these 34 units, 18 were excited orthodromically by stimulation of the CSN and/or ADN. Furthermore, 10 of the 18 units responding to stimulation of the buffer nerves were also orthodromically excited by stimulation of NTS. An additional 76 units were identified in VLM that only responded orthodromically to stimulation of NTS with a mean latency of9.75 ± 2.93ms, of which 33 also responded orthodromically to stimulation of the buffer nerves. These data provide electrophysiological evidence of a bidirectional connection between neurons in VLM that receive and integrate peripheral cardiovascular afferent inputs and send efferent axons directly back to the region of NTS. These results suggest that neurons in the VLM may be part of a medullary feedback reflex loop through which afferent information from cardiovascular receptors exerts an influence on NTS neurons involved in the control of the circulation.

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Projections from the nucleus tractus solitarii (NTS) to autonomic control regions of the ventrolateral medulla, particularly the nucleus reticularis rostroventrolateralis (RVL), which serves as a tonic vasomotor center, were analyzed in rat by anterograde, retrograde, and combined axonal transport techniques. Autonomic portions of the NTS, including its commissural, dorsal, intermediate, interstitial, ventral, and ventrolateral subnuclei directly project to RVL as well as to other regions of the ventrolateral medulla. The projections are organized topographically. Rostrally, a small cluster of neurons in the intermediate third of NTS, the subnucleus centralis, and neurons in proximity to the solitary tract selectively innervate neurons in the retrofacial nucleus and nucleus ambiguus. Neurons generally located in more caudal and lateral sites in the NTS innervate the caudal ventrolateral medulla (CVL). The RVL, CVL, and nucleus retroambiguus are interconnected. A combined retrograde and anterograde transport technique was developed so as to prove that projections from NTS to the ventrolateral medulla specifically innervate the region of RVL containing neurons projecting to the thoracic spinal cord or the region of the nucleus containing vagal preganglionic neurons. When the retrograde tracer, fast blue, was injected into the thoracic spinal cord, and wheat germ agglutinin-conjugate horseradish peroxidase (HRP) was injected into the NTS, anterogradely labeled terminals from the NTS surrounded the retrogradely labeled neurons in the RVL and in the nucleus retroambiguus in the caudal medulla. Among the bulbospinal neurons in the RVL innervated by the NTS were adrenaline-synthesizing neurons of the C1 group. When fast blue was applied to the cervical vagus, and HRP was injected into the NTS, anterogradely labeled terminals from the NTS surrounded retrogradely labeled neurons in the rostral dorsal motor nucleus of the vagus, the region of the nucleus ambiguus, the retrofacial nucleus, and the dorsal portion of the RVL, a region previously, shown to contain cardiac vagal preganglionic neurons. This combined anterograde and retrograde transport technique provides a useful method; for tracing disynaptic connections in the brain. These data suggest that the RVL is part of a complex of visceral output regions in the ventrolateral medulla, all of which receive afferent projections from autonomic portions of the NTS. Bulbospinal neurons in the RVL, in particular the C1 adrenaline neurons, may provide a portion of the anatomic substrate of the baroreceptor and other visceral reflexes.

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Jun 1986

R Miles

Afferent fibers from visceral sensory receptors enter the medulla oblongata, form the solitary tract, and synapse with neurons in the nucleus of the solitary tract. In the present study longitudinal slices were prepared from guinea pig medulla in order to examine the properties of transmission at these synapses in vitro. Synaptic responses to selective stimulation of solitary tract fibers were recorded intracellularly from neurons in an area, close to the obex and immediately medial and lateral to the tract, where arterial baroreceptor fibers are known to terminate. The amplitude of maximally evoked postsynaptic potentials (PSPs) in solitary tract neurons was strongly dependent on stimulus frequency. On increasing frequency from 0.5 to 20 Hz, a PSP depression of 80% was reached in 4-8 s. The mean depression was 35% at 5 Hz and 60% at 10 Hz. Sufficient local connections were retained in vitro that solitary tract stimulation evoked disynaptic inhibitory potentials and long latency, possibly polysynaptic, excitatory potentials in some neurons. The possibility that frequency-dependent changes in the efficacy of these local synaptic circuits contributed to PSP depression was examined. The role of postsynaptic inhibition in synaptic depression was tested by examining the frequency dependence of PSPs at membrane potentials close to the reversal of their excitatory component. The resulting hyperpolarizing PSPs were also depressed suggesting that a facilitation of postsynaptic inhibition at high frequency does not underlie the depression. The contribution of depression in multisynaptic excitatory pathways to PSP depression was assessed by exclusion. At low stimulus intensities, excitatory synaptic events with no long latency components were evoked. These events exhibited a similar frequency dependence to that of maximal PSPs. These results suggest that mechanisms operating at synapses made by solitary tract fibers are responsible for the frequency dependence of PSPs recorded in solitary tract neurons. Such mechanisms might contribute to the adaptation of some cardiovascular reflexes initiated by baroreceptors.

Post-synaptic activity evoked in the nucleus tractus solitarius by carotid sinus and aortic nerve afferents in the cat

Article

Apr 1985

Post-synaptic responses evoked in neurones of the nucleus tractus solitarius by electrical stimulation of the carotid sinus, aortic and vagal nerves, alone or in combination, have been studied in anaesthetized cats using both extracellular and intracellular recording techniques. A total of 292 neurones received an input from at least one of the three nerves tested. The activity of the large majority of these cells (249) could only be shown to be altered by stimulation of one of these nerves and in 222 of these cases this was an excitatory response. These responses showed the expected post-synaptic characteristics including temporal summation and, in intracellular records, a summation of evoked excitatory post-synaptic potentials (e.p.s.p.s). The minimum latency to onset of these responses was variable, both for individual cells and for the population as a whole and varied within the range 2-124 ms. In a small number of cells (twenty-seven), the input was purely inhibitory in nature. In neurones showing a tonic discharge this produced a decrease in the rate of firing. This influence was most marked in intracellular records where membrane hyperpolarizations were noted. Again, the latency to onset was variable, in the range 4-27 ms. Convergent inputs from two or more of the nerves were identified in forty-three neurones. The effects of these were always excitatory. They could be observed both as a facilitation of spike activity recorded extracellularly and as summation of subliminally evoked e.p.s.p.s recorded intracellularly. On the basis of threshold voltages and latency to onset, the afferents to these neurones are indistinguishable from those providing an exclusive input. It can be concluded that at least some of the neurones in the nucleus tractus solitarius and its vicinity receive inputs from more than one source. The implications of these observations on the role of this brain-stem area in cardiorespiratory reflexes is discussed.

The organization of noradrenergic pathways from the brainstem to the paraventricular and supraoptic nuclei in the rat

Article

Dec 1982
BRAIN RES

Axonal transport and immunohistochemical methods have been used to clarify the organization of pathways from noradrenergic and adrenergic cell groups in the brainstem to the paraventricular (PVH) and supraoptic (SO) nuclei of the hypothalamus. First, the location of such cells was determined with a combined retrograde tracer-immunofluorescence method. The fluorescent tracer, True Blue, was injected into the PVH or the SO, and sections through the brainstem were stained with anti-(rat) DBH, a specific marker for noradrenergic and adrenergic neurons. It was found that, after injections in the PVH, doubly labeled neurons were confined almost exclusively to 3 cell groups, the A1 region of the ventral medulla, which contained a majority of such cells, the A2 region in the dorsal vagal complex, and the locus coeruleus (A6 region). After injections centered in the SO an even greater proportion of doubly labeled cells were found in the A1 region, although some were also found in the A2 and A6 regions. The topography of doubly labeled cells indicates that these projections arise primarily from noradrenergic neurons, although adrenergic cells in both the C1 and the C2 groups probably contribute as well. Because well over 80% of the retrogradely labeled cells in these three regions were also DBH-positive, we next placed injections of [3H]amino acids into each of them in different groups of animals, and traced the course and distribution of the ascending (presumably DBH-positive) projections to the PVH and SO in the resulting autoradiograms. Injections centered in the A1 region labeled a substantial projection to most parts of the parvocellular division of the PVH, and was most dense in the dorsal and medial parts. In addition, terminal fields were labeled on those parts of the magnocellular division of the PVH, and of the SO, in which vasopressinergic cell bodies are concentrated. Injections centered in the A2 region also labeled a projection to the parvocellular division of the PVH that was topographically similar, but less dense, than that from the A1 region. In contrast, [3H]amino acid injections centered in the locus coeruleus labeled a moderately dense projection to the PVH that was limited to the medialmost part of the parvocellular division. Neither the A2 nor the A6 cell groups project to the magnocellular parts of PVH, or to the SO. The autoradiographic material, and additional double-labeling experiments, were used to identify and to characterize projections that interconnect the A1, A2 and A6 regions, as well as possible projections from these cell groups to the spinal cord. These results may be summarized as follows: a substantial projection from the nucleus of the solitary tract to the A1 region was identified, but this pathway does not arise from catecholaminergic neurons in the A2 cell group. DBH-stained cells in the A1 region project back to the dorsal vagal complex, as well as quite massively to the locus coeruleus (A6 region)...

Spontaneous synaptic activities in rat nucleus tractus solitarius neurons in vitro: Evidence for re-excitatory processing

Article

Jan 1994
BRAIN RES

The pattern of synaptic interactions between neurons of the nucleus tractus solitarius (NTS) has been analyzed using whole cell recording in rat brainstem slices. Following tractus solitarius (TS) stimulation 15/55 neurons presented a prolonged (up to 300 ms) increased excitability (PIE neurons) and 40/55 neurons presented a prolonged (up to 200 ms) reduced excitability (PRE neurons). In the absence of afferent sensory input all neurons showed spontaneous synaptic activity. Ongoing synaptic activity in PIE cells was glutamatergic and characterized by the absence of detectable inhibitory potentials while in PRE cells it was 90% GABAergic and 10% glutamatergic. Glutamatergic synaptic currents in PIE cells and GABAergic synaptic currents in PRE were studied using probability density and intensity functions. Distribution of time intervals between synaptic events indicated the latter were generated, in both PIE and PRE cells, by two simultaneous processes: (1) a close to Poisson process generating independent events; and (2) a subsidiary re-excitatory process generating synaptic events separated by intervals shorter than 20 ms. Blockade of glutamatergic transmission by 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 microM) or blockade of action potentials by tetrodotoxin (TTX; 1 microM) suppressed the subsidiary process. In conclusion, we propose that PIE cells (1) form a re-excitatory network contributing to generation of excitatory activity in the NTS and (2) are located presynaptically with respect to PRE cells.

Rostral ventrolateral medulla descending neurons excited by nucleus tractus solitarii inputs

Article

Jul 1994
BRAIN RES

Antonio R. Granata

Neurons in the rostral ventrolateral medulla (RVLM) were electrophysiologically characterized and anatomically identified using an intracellular recording technique in vivo. Of 49 neurons recorded, 7 were antidromically activated from the dorsolateral funiculus in the thoracic spinal cord, with axonal conduction velocities ranging from 16.6 to 55.0 m/s. The RVLM-spinal neurons were spontaneously active and non-bursting. Additionally, they demonstrated a flat post-R-wave histogram and a flat average of the neuronal membrane potential triggered by the pulsatile arterial pressure. Therefore their activity was not related to cardiac rhythm. Electrical stimulation of the nucleus tractus solitarii (NTS) at the level of the obex evoked monosynaptic excitatory postsynaptic potential (EPSP) on 3 RVLM-spinal neurons; median latency was 1.5 ms. The recorded neurons, intracellularly labeled with horseradish peroxidase (HRP) or biocytin, were located in the rostral pole of the RVLM, between 0.3 and 0.7 mm from the ventral medullary surface and in many cases close to the neurons containing phenylethanolamine-N-methyltransferase (PNMT). These findings are discussed in relation to the physiological role in cardiovascular and nociceptive functional regulation played by the neurons analyzed in this study.

Annual Review Prize Lecture. Central nervous mechanisms contributing to cardiovascular control

Article

Feb 1994

Kenneth M Spyer

Relationship of calbindin D-28k with afferent neurons to the rostral ventrolateral medulla in the rat

Article

Jun 1994
BRAIN RES

The phenylethanolamine-N-methyltransferase (PNMT)-containing neurons in the rostral ventrolateral medulla (RVLM) (the C1 adrenergic group) have been implicated in the generation of the tonic sympathetic nerve activity. Using a double-labeling immunohistofluorescence technique, we found that 34.6 +/- 11.4% (mean +/- S.D.) of PNMT immunoreactive neurons in the RVLM were immunoreactive for Calbindin D-28k (CaBP), a Vitamin D-dependent calcium binding protein. Since CaBP is probably involved in regulating intracellular calcium concentrations in cells that are metabolically or electrically very active, our results suggest that at least some C1 adrenergic neurons (those containing calbindin) may have calcium mediated high metabolic or electrophysiologic activity that is associated with generating tonic nerve function. The RVLM has wide connections with many different nuclei in the brain which are known to contain clusters of neurons that express immunoreactivity to CaBP. In order to determine whether CaBP could be used as a molecular marker for projection neurons to the RVLM or to identify a subpopulation of projection neurons containing CaBP, we sought to determine the relationships between CaBP and the neurons that project to RVLM. Following injections of the retrograde tracer FluoroGold (FG) into the rat RVLM, sections containing retrogradely labeled neurons in (1) the nucleus tractus solitarii (NTS), (2) the contralateral RVLM, (3) the area postrema, (4) the mesencephalic central gray (mCG), (5) the lateral hypothalamus (LH), (6) the substantia innominata (SI), and (7) the paraventricular hypothalamic nucleus (PV) were tested for CaBP immunoreactivity. Although many retrogradely labeled neurons were found amidst many CaBP immunoreactive neurons in each of these nuclei, only a subpopulation of the retrogradely labeled neurons expressed CaBP immunoreactivity. The NTS demonstrated the higher proportion of double-labeled cells (mean 31.5 +/- 4.3%), whereas the lower proportion corresponded to the contralateral RVLM (mean 9.6 +/- 3.2%). On the other hand, both the retrogradely labeled neurons and the CaBP immunoreactive neurons in each of these nuclei were often found in regions containing a great number of adrenergic axons (i.e. immunoreactive for PNMT). Our results suggest that: (1) Two types of adrenergic RVLM neurons could be found, those containing CaBP and those lacking this calcium binding protein. (2) CaBP is not a common marker for the afferent neurons to the RVLM, but rather is found in selective subsets of them. (3) Both the non-CaBP projection neurons and the CaBP immunoreactive neurons in these nuclei may be innervated by adrenergic fibers.

Electrophysiological and morphological characteristics of nucleus tractus solitarii neurons projecting to the ventrolateral medulla

Abstract

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