Neurons In Medulla Research Articles

The connectome of rostral ventrolateral medulla sympathetic premotor neurons

Spinally projecting neurons in the rostral ventrolateral medulla (RVLM) are thought to play a critical role in the generation of vasomotor sympathetic tone and represent a major site of convergence for multiple descending and reflex pathways that co-ordinate sympathetic nerve activity. Elucidating the organization of the circuits that drive these neurons is a key research objective. Here we present brain-wide connectomic maps of neurons that provide monosynaptic drive to putative RVLM sympathetic premotor neurons, generated using a two-step restricted trans-synaptic viral tracing strategy. We made focal microinjections of a genetically restricted reporter-expressing rabies vector, SADΔG(EnvA)-RFP, into the RVLM, and restricted its entry to neurons that project to the T2 spinal cord by first transducing them with a cassette required for rabies entry and trans-synapsis, YTB. By precisely targeting rabies injections to the core of the RVLM bulbospinal population we were able to restrict rabies ‘seeding’ to small numbers (as low as one single neuron) of RVLM presympathetic neurons immediately caudal to the facial nucleus, and then map the locations of neurons that provide monosynaptic input to the seed population. We observed reproducible patterns of inputs arising from the dorsal, contralateral, and midline medulla, and local RVLM interneurons including catecholaminergic non-bulbospinal neurons and neurons likely to reside within the ventral respiratory column. Distant inputs were identified in the pons, cerebellum and midbrain, and included previously suspected sites of monosynaptic drive such as the paraventricular nucleus of the hypothalamus.

Putative sympathetic premotor neurons in the rostral ventrolateral medulla are not somatotopically distributed

Putative sympathetic premotor neurons in the rostral ventrolateral medulla are not somatotopically distributed

Control of REM sleep by ventral medulla GABAergic neurons.

Rapid eye movement (REM) sleep is a distinct brain state characterized by activated electroencephalogram (EEG) and complete skeletal muscle paralysis, and it is associated with vivid dreams1-3. Transection studies by Jouvet first demonstrated that the brainstem is both necessary and sufficient for REM sleep generation2, and the neural circuits in the pons have since been studied extensively4-8. The medulla also contains neurons that are active during REM sleep9-13, but whether they play a causal role in REM sleep generation remains unclear. Here we show that a GABAergic pathway originating from the ventral medulla (vM) powerfully promotes REM sleep. Optogenetic activation of vM GABAergic neurons rapidly and reliably initiated REM sleep episodes and prolonged their durations, whereas inactivating these neurons had the opposite effects. Optrode recordings from channelrhodopsin 2 (ChR2)-tagged vM GABAergic neurons showed that they were most active during REM sleep (REM-max), and during wakefulness they were preferentially active during eating and grooming. Furthermore, dual retrograde tracing showed that the rostral projections to the pons and midbrain and caudal projections to the spinal cord originate from separate vM neuron populations. Activating the rostral GABAergic projections was sufficient for both the induction and maintenance of REM sleep, which are likely mediated in part by inhibition of REM-suppressing GABAergic neurons in the ventrolateral periaqueductal gray (vlPAG). These results identify a key component of the pontomedullary network controlling REM sleep. The capability to induce REM sleep on command may offer a powerful tool for investigating its functions.

Cerebrospinal Fluid Hypernatremia Elevates Sympathetic Nerve Activity and Blood Pressure via the Rostral Ventrolateral Medulla.

Elevated NaCl concentrations of the cerebrospinal fluid increase sympathetic nerve activity (SNA) in salt-sensitive hypertension. Neurons of the rostral ventrolateral medulla (RVLM) play a pivotal role in the regulation of SNA and receive mono- or polysynaptic inputs from several hypothalamic structures responsive to hypernatremia. Therefore, the present study investigated the contribution of RVLM neurons to the SNA and pressor response to cerebrospinal fluid hypernatremia. Lateral ventricle infusion of 0.15 mol/L, 0.6 mol/L, and 1.0 mol/L NaCl (5 µL/10 minutes) produced concentration-dependent increases in lumbar SNA, adrenal SNA, and arterial blood pressure, despite no change in splanchnic SNA and a decrease in renal SNA. Ganglionic blockade with chlorisondamine or acute lesion of the lamina terminalis blocked or significantly attenuated these responses, respectively. RVLM microinjection of the gamma-aminobutyric acid (GABAA) agonist muscimol abolished the sympathoexcitatory response to intracerebroventricular infusion of 1 mol/L NaCl. Furthermore, blockade of ionotropic glutamate, but not angiotensin II type 1, receptors significantly attenuated the increase in lumbar SNA, adrenal SNA, and arterial blood pressure. Finally, single-unit recordings of spinally projecting RVLM neurons revealed 3 distinct populations based on discharge responses to intracerebroventricular infusion of 1 mol/L NaCl: type I excited (46%; 11/24), type II inhibited (37%; 9/24), and type III no change (17%; 4/24). All neurons with slow conduction velocities were type I cells. Collectively, these findings suggest that acute increases in cerebrospinal fluid NaCl concentrations selectively activate a discrete population of RVLM neurons through glutamate receptor activation to increase SNA and arterial blood pressure.

Sex differences in NMDA GluN1 plasticity in rostral ventrolateral medulla neurons containing corticotropin-releasing factor type 1 receptor following slow-pressor angiotensin II hypertension

There are profound, yet incompletely understood, sex differences in the neurogenic regulation of blood pressure. Both corticotropin signaling and glutamate receptor plasticity, which differ between males and females, are known to play important roles in the neural regulation of blood pressure. However, the relationship between hypertension and glutamate plasticity in corticotropin-releasing factor (CRF)-receptive neurons in brain cardiovascular regulatory areas, including the rostral ventrolateral medulla (RVLM) and paraventricular nucleus of the hypothalamus (PVN), is not understood. In the present study, we used dual-label immuno-electron microscopy to analyze sex differences in slow-pressor angiotensin II (AngII) hypertension with respect to the subcellular distribution of the obligatory NMDA glutamate receptor subunit 1 (GluN1) subunit of the N-methyl-d-aspartate receptor (NMDAR) in the RVLM and PVN. Studies were conducted in mice expressing the enhanced green fluorescence protein (EGFP) under the control of the CRF type 1 receptor (CRF1) promoter (i.e., CRF1–EGFP reporter mice). By light microscopy, GluN1-immunoreactivity (ir) was found in CRF1–EGFP neurons of the RVLM and PVN. Moreover, in both regions tyrosine hydroxylase (TH) was found in CRF1–EGFP neurons. In response to AngII, male mice showed an elevation in blood pressure that was associated with an increase in the proportion of GluN1 on presumably functional areas of the plasma membrane (PM) in CRF1–EGFP dendritic profiles in the RVLM. In female mice, AngII was neither associated with an increase in blood pressure nor an increase in PM GluN1 in the RVLM. Unlike the RVLM, AngII-mediated hypertension had no effect on GluN1 localization in CRF1–EGFP dendrites in the PVN of either male or female mice. These studies provide an anatomical mechanism for sex-differences in the convergent modulation of RVLM catecholaminergic neurons by CRF and glutamate. Moreover, these results suggest that sexual dimorphism in AngII-induced hypertension is reflected by NMDA receptor trafficking in presumptive sympathoexcitatory neurons in the RVLM.

Mechanisms of ventilatory control: who is really in charge?

Mechanisms of ventilatory control: who is really in charge?

Lesion of medullary catecholaminergic neurons is associated with cardiovascular dysfunction in rotenone-induced Parkinson's disease rats.

In recent years, non-motor symptoms have been recognised as of vital importance in Parkinson's disease (PD); among these, cardiovascular dysfunctions are commonly seen in PD patients before their motor signs. The role of cardiovascular dysfunction in the progression of PD pathology, and its underlying mechanisms, are largely unknown. In the present study, in rotenone-induced PD rats, there was a gradual reduction in the number of nigral tyrosine hydroxylase-immunoreactive (TH-ir) neurons after 7, 14 and 21 days treatment. With the 56% reduction in striatal dopamine content and 52% loss of TH-ir neurons on the 14th day, the rats showed motor dysfunctions. However, from ECG power spectra, reductions in normalised low-frequency power and in the low-frequency power : high-frequency power ratio, as well as in mean blood pressure, were observed as early as the 3rd day. Plasma norepinephrine (NE) and epinephrine (E) levels were decreased by 39% and 26% respectively at the same time. Pearson's correlation analysis showed that both plasma NE and plasma E levels were positively correlated with MBP. Our results also showed that the loss of catecholaminergic neurons in the rostral ventrolateral medulla (RVLM), but not in the caudal ventrolateral medulla or the nucleus tractus solitarii, emerged earlier than the loss of nigral dopaminergic neurons. This suggests that dysfunction of catecholaminergic neurons in the RVLM might account for the reduced sympathetic activity, MBP and plasma catecholamine levels in the early stages of PD.

Uric acid, indoxyl sulfate, and methylguanidine activate bulbospinal neurons in the RVLM via their specific transporters and by producing oxidative stress

Patients with chronic renal failure often have hypertension, but the cause of hypertension, other than an excess of body fluid, is not well known. We hypothesized that the bulbospinal neurons in the rostral ventrolateral medulla (RVLM) are stimulated by uremic toxins in patients with chronic renal failure. To investigate whether RVLM neurons are sensitive to uremic toxins, such as uric acid, indoxyl sulfate, or methylguanidine, we examined changes in the membrane potentials (MPs) of bulbospinal RVLM neurons of Wister rats using the whole-cell patch-clamp technique during superfusion with these toxins. A brainstem-spinal cord preparation that preserved the sympathetic nervous system was used for the experiments. During uric acid, indoxyl sulfate, or methylguanidine superfusion, almost all the RVLM neurons were depolarized. To examine the transporters for these toxins on RVLM neurons, histological examinations were performed. The uric acid-, indoxyl sulfate-, and methylguanidine-depolarized RVLM neurons showed the presence of urate transporter 1 (URAT 1), organic anion transporter (OAT)1 or OAT3, and organic cation transporter (OCT)3, respectively. Furthermore, the toxin-induced activities of the RVLM neurons were suppressed by the addition of an anti-oxidation drug (VAS2870, an NAD(P)H oxidase inhibitor), and a histological examination revealed the presence of NAD(P)H oxidase (nox)2 and nox4 in these RVLM neurons. The present results show that uric acid, indoxyl sulfate, and methylguanidine directly stimulate bulbospinal RVLM neurons via specific transporters on these neurons and by producing oxidative stress. These uremic toxins may cause hypertension by activating RVLM neurons.

Activation of α1-adrenoceptors facilitates excitatory inputs to medullary airway vagal preganglionic neurons.

In mammals, the neural control of airway smooth muscle is dominated by a subset of airway vagal preganglionic neurons in the ventrolateral medulla. These neurons are physiologically modulated by adrenergic/noradrenergic projections, and weakened α₂-adrenergic inhibition of them is indicated to participate in the pathogenesis and exacerbation of asthma. This study tests whether these neurons are modulated by α₁-adrenoceptors, and if so, how. In anesthetized adult rats, microinjection of the α₁A-adrenoceptor agonist A61603 (1 pmol) unilaterally into the medullary region containing these neurons caused a significant increase in airway resistance, which was prevented by intraperitoneal atropine (0.5 mg/kg). In rhythmically firing medullary slices of newborn rats, A61603 (10 nM) caused depolarization in both the inspiratory-activated and inspiratory-inhibited airway vagal preganglionic neurons that were retrogradely labeled, and a significant increase in the spontaneous firing rate. Under voltage clamp, A61603 significantly enhanced the spontaneous excitatory inputs to both types of neurons and caused a tonic inward current in the inspiratory-activated neurons along with significantly increased peak amplitude of the inspiratory inward currents. The responses in vitro were prevented by α₁A-adrenoceptor antagonist RS100329 (1 μM), which alone significantly inhibited the spontaneous excitatory inputs to both types of the neurons. After pretreatment with tetrodotoxin (1 μM), A61603 (10 or 100 nM) had no effect on either type of neuron. We conclude that in rats, activation of α₁-adrenoceptors in the medullary region containing airway vagal preganglionic neurons increases airway vagal tone, and that this effect is primarily mediated by facilitation of the excitatory inputs to the preganglionic neurons.

REM Sleep at its Core - Circuits, Neurotransmitters, and Pathophysiology.

Rapid eye movement (REM) sleep is generated and maintained by the interaction of a variety of neurotransmitter systems in the brainstem, forebrain, and hypothalamus. Within these circuits lies a core region that is active during REM sleep, known as the subcoeruleus nucleus (SubC) or sublaterodorsal nucleus. It is hypothesized that glutamatergic SubC neurons regulate REM sleep and its defining features such as muscle paralysis and cortical activation. REM sleep paralysis is initiated when glutamatergic SubC cells activate neurons in the ventral medial medulla, which causes release of GABA and glycine onto skeletal motoneurons. REM sleep timing is controlled by activity of GABAergic neurons in the ventrolateral periaqueductal gray and dorsal paragigantocellular reticular nucleus as well as melanin-concentrating hormone neurons in the hypothalamus and cholinergic cells in the laterodorsal and pedunculo-pontine tegmentum in the brainstem. Determining how these circuits interact with the SubC is important because breakdown in their communication is hypothesized to underlie narcolepsy/cataplexy and REM sleep behavior disorder (RBD). This review synthesizes our current understanding of mechanisms generating healthy REM sleep and how dysfunction of these circuits contributes to common REM sleep disorders such as cataplexy/narcolepsy and RBD.

Lipopolysaccharide stimulation upregulated Toll-like receptor 4 expression in chicken cerebellum

Toll-like receptors (TLRs) play crucial roles in innate and adaptive immune responses to invading pathogens. TLR4 is responsible for the recognition of bacterial lipopolysaccharide (LPS) in different parts of central nervous system of many vertebrates. To better understand the functions of TLR4 in cerebellum of chicken, present study was designed to identify the cell types that express TLR4 during postnatal stages as well as the changes in its expression in response to LPS challenge. For this purpose, cerebella were collected from chicken aged 1, 14 and 40 days (n=7 in each group) to analyze TLR4 distribution pattern. The cerebella from 14 chickens injected with LPS or sterilizing saline were also collected at Day 14 (n=7 in each group) to investigate changes in TLR4 expression. This expression was analyzed by immunohistochemistry using an anti-TLR4 antibody. TLR4 was constitutively expressed in the Purkinje cell layer, pia mater, neurons in medulla and blood vessels in the cerebellum and LPS stimulation significantly up-regulated TLR4 expression on Day 14 in the chicken cerebellum. This study provides evidence that neurons in chicken cerebellum can express TLR4 in vivo and suggests that these neurons may play an important role in initiating a defense reaction via activation of TLR4.

ATP stimulates rat hypothalamic sympathetic neurons by enhancing AMPA receptor-mediated currents.

We have previously shown that ATP within the paraventricular nucleus (PVN) induces an increase in sympathetic activity, an effect attenuated by the antagonism of P2 and/or glutamatergic receptors. Here, we evaluated precise cellular mechanisms underlying the ATP-glutamate interaction in the PVN and assessed whether this receptor coupling contributed to osmotically driven sympathetic PVN neuronal activity. Whole-cell patch-clamp recordings obtained from PVN-rostral ventrolateral medulla neurons showed that ATP (100 μM, 1 min, bath applied) induced an increase in firing rate (89%), an effect blocked by kynurenic acid (1 mM) or 4-[[4-Formyl-5-hydroxy-6-methyl-3-[(phosphonooxy)methyl]-2-pyridinyl]azo]-1,3-benzenedisulfonic acid tetrasodium salt (PPADS) (10 μM). Whereas ATP did not affect glutamate synaptic function, α-amino-3-hydroxy-5-methylisoxazole propionic acid (AMPA) receptor-mediated currents evoked by focal application of AMPA (50 μM, n = 13) were increased in magnitude by ATP (AMPA amplitude: 33%, AMPA area: 52%). ATP potentiation of AMPA currents was blocked by PPADS (n = 12) and by chelation of intracellular Ca(2+) (BAPTA, n = 10). Finally, a hyperosmotic stimulus (mannitol 1%, +55 mosM, n = 8) potentiated evoked AMPA currents (53%), an effect blocked by PPADS (n = 6). Taken together, our data support a functional stimulatory coupling between P2 and AMPA receptors (likely of extrasynaptic location) in PVN sympathetic neurons, which is engaged in response to an acute hyperosmotic stimulus, which might contribute in turn to osmotically driven sympathoexcitatory responses by the PVN.

Activation of a Small Cluster of Excitatory Neurons in the Medial Medulla Induces a Phenotype that Resembles Cervical Dystonia (P4.323)

Activation of a Small Cluster of Excitatory Neurons in the Medial Medulla Induces a Phenotype that Resembles Cervical Dystonia (P4.323)

Renal Tissue Blood Flow Regulation System in Acute Blood Pressure Modulation is Maintained in Elderly Wistar‐Kyoto Rats

Back ground: Systemic arterial pressure is maintained by sympathetic vasomotor tone regulated by autonomic nerve system. Therefore, attenuation of systemic arterial pressure causes reduction of peripheral tissue blood flow. On the other hand, renal tissue has specific blood flow regulatory system to maintain constant renal blood flow involving autonomic regulatory system. However, the effect of aging in maintenance of renal tissue blood flow regulatory system was not fully established. In this study, we used elderly Wistar-Kyoto (WKY) rats as an aged normotensive animal model, examined relation between systemic arterial pressure modulation and renal tissue blood flow regulation. Method: Aged WKY rats (56w-80w) and control group (16-24w) were anesthetized with chloralose, the arterial pressure, pulse rate and renal tissue blood flow were measured simultaneously. Results: Arterial pressure modulation by intravenous injection of phenylephrine, sodium nitroprusside and the activation of sympathetic vasomotor neurons in rostral ventrolateral medulla were not effected to renal tissue blood flow neither aged group nor control, although baro-reflex was attenuated in aged group. Conclusion These results suggest that renal tissue blood flow regulatory system was maintained in aged normotensive animals, though baro-receptor dependent systemic arterial pressure regulatory system was attenuated. Therefore, although in aged animals, renal tissue autonomic blood flow regulatory system still play important role.

Electrophysiological property of spinally projecting serotonergic neurons in the rostroventromedial medulla in transgenic mice expressing green fluorescent protein.

Electrophysiological property of spinally projecting serotonergic neurons in the rostroventromedial medulla in transgenic mice expressing green fluorescent protein.

NPY is Co‐localized with TH in Ventrolateral Medullary Neurons Projecting to the Hypothalamus in Mice

The catecholamine (CA) neurons of the ventrolateral medulla (VLM) are activated by many visceral stressors, including hypovolemia, hypoxia, hypoglycemia and infection and their activation results in equally diverse physiological output, including elevated BP, ventilation, arousal and neuroendocrine activation. In the rat, we previously described two subsets of VLM‐CA neurons: spinal‐ and hypothalamic‐projecting. In the current study we have identified the same subsets in mice. We distinguished between two VLM‐CA subtypes by rostral‐caudal location and neuropeptide Y (NPY) expression. In mice, Fluorogold (FG) was injected into either the spinal cord or paraventricular nucleus of the hypothalamus to identify spinal‐projecting and hypothalamic‐projecting VLM‐CA neurons, respectively. After allowing 5‐7 days for retrograde transport, the mice were perfused and brains processed for combined immunohistochemistry and in situ hybridization (ISH) to visualize VLM‐CA neuronal somata (TH‐ir) containing FG and NPY (ISH). We found that more than half (66.1 ± 2.5 %, n = 8) of the VLM‐CA neurons are positive for NPY mRNA. Spinal‐projecting VLM‐CA neurons generally resided more rostral, just behind and medial to the facial nucleus, and did not express NPY mRNA (0.5 ± 0.3 %, n = 4).Conversely, hypothalamic‐projecting VLM‐CA neurons were located slightly more caudal and most expressed NPY mRNA (63.8 ± 19.6 %, n = 3). In addition, over 90 % (n = 8) of NPY‐positive neurons co‐expressed TH, indicating that, within the mouse VLM, NPY is predominantly expressed by VLM‐CA neurons. NPY expression is a selective marker for hypothalamic‐projecting VLM‐CA neurons in mice as well as rats.

Leptin Inhibits Presympathetic Neurons in the Rostral Ventrolateral Medulla

Leptin is greatly involved in the regulation of food intake, and dysfunction of leptin or its receptors is associated with obesity. Numerous evidence indicate that obesity is linked to increased prevalence of hypertension. The sympathetic nervous system (SNS) is greatly involved in the regulation of arterial blood pressure and neurons in the rostral ventrolateral medulla (RVLM) are critical components of both the SNS and cardiovascular regulation. In this study we used whole-cell patch-clamp recordings from presympathetic kidney-related RVLM neurons identified with retrograde viral labeling and tested the hypothesis that leptin reduces neuronal excitability of RVLM neurons. Application of leptin (500 nM) caused a rapid membrane hyperpolarization (3.7 ± 1.4 mV change) in half of the recorded presympathetic RVLM neurons without affecting the rest of the recorded cells. The hyperpolarization was accompanied with an increase of input resistance from 287 ± 95 MΩ to 336 ± 97 MΩ. In addition, leptin decreased the frequency of spontaneous excitatory postsynaptic currents (sEPSC) by 35.6 ± 0.1% without changing sEPSC amplitude. In contrast, leptin did not alter the inhibitory neurotransmission. In summary, our data demonstrate that leptin reduces the excitability of a subset of presympathetic RVLM neurons via pre- and postsynaptic mechanisms and suggest a potential control mechanism of SNS activity. Supported by Tulane University COBRE in Hypertension (NIH P30GM103337).

Spectral Analysis of Barosensitive Neurons in the Rat Rostral Ventrolateral Medulla

Regulation of blood pressure occurs primarily via the activity of bulbospinal rostral ventrolateral medulla (RVLM) neurons that drive sympathetic nerve activity (SNA). Central and peripheral stimuli influence the activity of RVLM neurons and are reflected in their cardiac and respiratory modulation. Dysregulation of RVLM neurons can lead to increased SNA and the development and maintenance of cardiovascular disease. In this study we used spectral (frequency‐domain) analysis to identify cardiac‐ and/or respiratory‐related (CR, RR) activity in barosensitive RVLM neurons (n=22) and splanchnic SNA of 16 Inactin‐anesthetized rats in which we also recorded arterial pressure (AP) and an index of respiration. SNA had RR activity (0.40±0.05; mean ± SE) and/or CR activity (0.63±0.05) as evidenced by a coherence value > 0.1 at the frequency of respiration and the heart rate, respectively, in the corresponding coherence functions. RVLM unit activity was also shown to be RR (0.40±0.14; n=4) or CR (0.41±0.07; n=4). Moreover, RVLM unit activity cohered to SNA at the frequency of the heart rate (0.39±0.08; n=4) or respiration (0.21; n=1). AP‐triggered analysis (time‐domain analysis) revealed CR activity in 4 other RVLM neurons. These data demonstrate our ability to study the relationships among rat RVLM unit activity, SNA, AP, and respiration, which will allow us to explore whether differences in the strengths of these relationships contribute to changes in SNA and AP under different physiological conditions.HL096787

The inhibitory effect of granisetron on ventrolateral medulla neuron responses to colorectal distension in rats

Irritable bowel syndrome (IBS) is one of the most widespread functional gastrointestinal disorders characterized by abdominal pain. A key pathophysiological mechanism of abdominal pain is associated with disturbances of serotonergic transmission in feedback control loops of endogenous pain modulation in which the ventrolateral medulla (VLM) plays an important role. The receptors to serotonin (5-HT), and particularly the serotonin 3 (5-HT3) receptors have been extensively used as a potential target for abdominal pain treatment of IBS patients due to antinociceptive features of the 5-HT3 receptor antagonists. The precise mechanisms underlying the antinociceptive action of these antagonists remain unclear. The main objective of our study was to evaluate the involvement of the 5-HT3 receptors in abdominal pain transmission within the VLM. Experiments were carried out on urethane-anaesthetized rats using the animal model of abdominal pain. Noxious colorectal distension (CRD) with a pressure of 80mmHg induced a significant increase in VLM neuron-evoked activity and depressor reactions (171.1±12.7% and 64±1.8% to baseline, accordingly). Selective blockade of the 5-HT3 receptors with granisetron at doses of 1.0 or 2.0mg/kg (i.v) resulted in long-lasting (90min) dose-dependent inhibition of VLM neuron-evoked activity and depressor reactions. When brainstem dorsal surface applications of granisetron (10 or 20µM) were used, the changes were more pronounced. These results suggest involvement of the 5-HT3 receptors in abdominal pain transmission within the VLM, which will be discussed in relation to the central antinociceptive effect of granisetron.

電気生理学的アプローチによる喉頭基礎研究

Laryngeal movements including breathing, phonation, and airway protective reflexes, such as swallowing and coughing, are mainly controlled by the neuronal networks in the brain stem. To understand the mechanisms underlying these movements, the morphological and functional properties of the brain stem neurons that participate in the production of these movements should be investigated. We previously examined the functional roles of the brain stem neurons that contribute to the generation of laryngeal movements using electrophysiological and morphological procedures. The findings of two studies are introduced in the presentation. In the first study, we reported the projections of the swallow-related neurons in the swallowing central pattern generator in the medulla oblongata using a tracer injection in anesthetized paralyzed guinea pigs. This study indicated that the swallowrelated neurons were broadly distributed in the nucleus tractus solitarius and reticular formation, and that there appeared to be complex interconnections amongst the nucleus tractus solitarius, the reticular formation, and the cranial motor nuclei. The other study showed that the activity of the respiratory neurons in the ventrolateral medulla, in particular between the Bötzinger complex and the rostral ventral respiratory group, was altered during fictive vocalization, swallowing, and coughing in a type-specific manner, and thus supported the hypothesis that the medullary respiratory neurons are multifunctional and that the respiratory center in the network circuitry underlying these behaviors can be shared.