Neurons in rostral VLM are inhibited by chemical stimulation of caudal VLM in rats

1989 ◽  
Vol 257 (2) ◽  
pp. R265-R270 ◽  
Author(s):  
S. K. Agarwal ◽  
A. J. Gelsema ◽  
F. R. Calaresu
Keyword(s):  
Direct Evidence ◽  
Cardiac Cycle ◽  
Ventrolateral Medulla ◽  
Sodium Glutamate ◽  
Inhibitory Pathway ◽  
Male Wistar Rats ◽  
Cardiovascular Neurons ◽  
Spontaneously Breathing ◽  
Baroreceptor Activation ◽  
Stimulation Of

Recent evidence suggests that neurons in the caudal ventrolateral medulla (CVLM) exert a tonic inhibition on the neurons in the rostral ventrolateral medulla (RVLM) that are essential for the maintenance of arterial pressure (AP). To test the hypothesis that selective activation of cell bodies in the CVLM can inhibit the discharge of neurons in the RVLM, activity from 88 neurons in the RVLM was recorded extracellularly while 2-30 nl sodium glutamate (Glu; 0.15 M) were microinjected into depressor sites of the CVLM of urethan-anesthetized male Wistar rats. Results obtained from spontaneously breathing and artificially ventilated rats were essentially similar and are presented together. Twenty-five neurons were characterized as cardiovascular because they were inhibited by baroreceptor activation and showed rhythmicity of their spontaneous activity in synchrony with the cardiac cycle. Activation of cell bodies in the CVLM inhibited the firing rate of 23 of these cardiovascular neurons and excited 2. The remaining 63 neurons could not be considered cardiovascular because they either were not barosensitive or lacked cardiac cycle-related rhythmicity. Injection of Glu into the CVLM inhibited 26 of these neurons, excited 22, and had no effect on 15. These results provide direct evidence for the existence of an inhibitory pathway from neurons located in the CVLM to cardiovascular neurons in the RVLM.

Inhibition of rostral VLM by baroreceptor activation is relayed through caudal VLM

1990 ◽  
Vol 258 (5) ◽  
pp. R1271-R1278 ◽  
Author(s):  
S. K. Agarwal ◽  
A. J. Gelsema ◽  
F. R. Calaresu
Keyword(s):  
Kynurenic Acid ◽  
Cardiac Cycle ◽  
Pressor Response ◽  
Inhibitory Response ◽  
Firing Frequency ◽  
Ventrolateral Medulla ◽  
Cardiovascular Neurons ◽  
Baroreceptor Activation ◽  
Acid Administration ◽  
Stimulation Of

Experiments were done to test the hypothesis that inhibition of neurons in the rostral ventrolateral medulla (RVLM) elicited by stimulation of the nucleus tractus solitarii (NTS) is relayed through the caudal ventrolateral medulla (CVLM). We recorded activity from 56 spontaneously firing units in the right RVLM of urethan-anesthetized and artificially ventilated rats. Eleven of these units were classified as cardiovascular neurons, because they were silenced by baroreceptor activation (1-3 micrograms phenylephrine iv) and showed rhythmicity of their spontaneous activity in synchrony with the cardiac cycle. Single pulses (0.1 ms, 30-75 microA) delivered 1/s to depressor sites in the ipsilateral NTS inhibited the activity of all these cardiovascular neurons. Microinjection of the glutamate antagonist kynurenic acid (0.15 M, 50 nl) into the ipsilateral CVLM blocked the inhibitory response of RVLM units to the administration of phenylephrine and increased the firing frequency of cardiovascular neurons in the RVLM by 43%. Moreover, kynurenic acid administration attenuated the inhibitory response of cardiovascular neurons in the RVLM to NTS stimulation. Finally, stimulation of the NTS that elicited depressor responses under control conditions produced a pressor response after kynurenic acid administration. The remaining 45 RVLM neurons were barosensitive but lacked cardiac cycle-related rhythmicity. These results provide direct evidence for the existence of a tonic inhibitory pathway from NTS to RVLM that is relayed through the CVLM probably by a glutamatergic projection from NTS to CVLM.

Pontine reticular neurons provide tonic excitation to neurons in rostral ventrolateral medulla in rats

1994 ◽  
Vol 266 (1) ◽  
pp. R237-R244 ◽  
Author(s):  
K. Hayes ◽  
F. R. Calaresu ◽  
L. C. Weaver
Keyword(s):  
Cardiac Cycle ◽  
Rostral Ventrolateral Medulla ◽  
Ventrolateral Medulla ◽  
Renal Nerve ◽  
Renal Nerve Activity ◽  
Cardiovascular Neurons ◽  
Reticular Neurons ◽  
Baroreceptor Activation ◽  
Tonic Excitation ◽  
Excitatory Drive

To determine whether the pontine reticular formation (PRF) is a source of tonic activity for cardiovascular neurons in the rostral ventrolateral medulla (RVLM), the discharge of PRF neurons was inhibited by unilateral microinjections of glycine (1.0 M; 60 nl) while recording the discharge of single neurons in the RVLM in 14 Saffan-anesthetized rats. RVLM units were characterized as cardiovascular if their spontaneous activity was changed by baroreceptor activation and was synchronized to the cardiac cycle. Glycine injection into the ipsilateral PRF eliminated the ongoing activity of six cardiovascular units and reduced the activity of four (mean decrease -91 +/- 4%). Inhibition of these units lasted 20-115 s (mean 59 +/- 9 s). Glycine injection into the PRF had no effect on the discharge of five cardiovascular units. Activity of six noncardiovascular units did not respond to PRF blockade. Glycine injection into the PRF caused decreases in arterial pressure (-28 +/- 5 mmHg), heart rate (-23 +/- 3 beats/min), and renal nerve activity (-42 +/- 7%) that also returned to control values between 25 and 120 s (mean 55 +/- 5 s). These results indicate that PRF neurons provide tonic excitatory drive to some cardiovascular neurons located in the RVLM.

In vivo study on medullary H(+)-sensitive neurons

1990 ◽  
Vol 69 (4) ◽  
pp. 1408-1412 ◽  
Author(s):  
N. Kogo ◽  
H. Arita
Keyword(s):  
Time Course ◽  
Direct Application ◽  
Ventrolateral Medulla ◽  
Similar Time ◽  
Central Chemoreceptors ◽  
Ph Dependent ◽  
Spontaneously Breathing ◽  
Medullary Neurons ◽  
Stimulation Of

Using the micro pressure ejection technique, we examined responses of medullary neurons with nonphasic discharges (164 units) to direct application of acidified mock cerebrospinal fluid (CSF, pH 6.85-7.05) in decerebrated spontaneously breathing cats. We found 16 H(+)-sensitive cells; they were excited promptly on application of approximately 500 pl of acidified mock CSF in the vicinity of the neuron under investigation, whereas they were unaffected by microejection of the control mock CSF (pH 7.25-7.60). Of the 16 H(+)-sensitive cells, 10 units were further found to be excited by transcapillary stimulation of the central chemoreceptors by using a method of intravertebral arterial injection of CO2-saturated saline. The discharges increased in a similar time course to that of ventilatory augmentation. Distributions of these 10 specific H(+)-sensitive cells were found in the vicinity of nucleus tractus solitarii as well as deep in the ventrolateral medulla. The present results suggest a possibility that pH-dependent central chemoreceptors, if any, would be located in two distinct medullary regions described in this study.

Lower brain stem controls cardiac ANF secretion

1992 ◽  
Vol 263 (1) ◽  
pp. H198-H207 ◽  
Author(s):  
J. H. Jiao ◽  
P. G. Guyenet ◽  
A. J. Baertschi
Keyword(s):  
Electrical Stimulation ◽  
Vehicle Control ◽  
Nucleus Ambiguus ◽  
Ventrolateral Medulla ◽  
Ventrolateral Nucleus ◽  
The Central Nervous System ◽  
Lower Brain Stem ◽  
Medullary Nuclei ◽  
Spontaneously Breathing ◽  
Stimulation Of

The purpose of these studies was to investigate whether the central nervous system (CNS) can modulate the plasma level of atrial natriuretic factor (ANF). In anesthetized, spontaneously breathing rats, electrical stimulation was stereotaxically applied bilaterally to four medullary nuclei: 1) the rostral nucleus of the solitary tract (rNTS), 2) the intermediate portion of the NTS (iNTS), 3) the ventrolateral nucleus ambiguus (NA) 0.3 mm rostral to obex, and 4) the rostral ventrolateral medulla (RVL). Electrical stimulation of the rNTS and RVL caused a 55 +/- 18% (P less than 0.025, n = 6) and 187 +/- 80% (P less than 0.001, n = 5) increase in plasma ANF, respectively, compared with baseline (56-88 pg/ml), whereas sham stimulations had no effect on plasma ANF release. In contrast, electrical stimulation of the iNTS and the NA elicited a 35 +/- 6 (P less than 0.01, n = 7) and 31 +/- 6% (P less than 0.05, n = 5) decrease in plasma ANF, respectively. In artificially ventilated rats, unilateral electrical stimulation of the RVL induced a 94 +/- 39 (left RVL, n = 6, P less than 0.01) and 186 +/- 68% (right RVL, P less than 0.01, n = 5) increase in plasma ANF over baseline. Unilateral microinjection of L-glutamate into RVL also resulted in a 81 +/- 23% (n = 9, P less than 0.01) increase in plasma ANF compared with baseline and vehicle control injections. These results suggest that activation of the central sympathetic system potently stimulates the secretion of cardiac ANF.

Role of ventrolateral medulla in reflex cardiovascular responses to activation of skin and muscle nerves

1995 ◽  
Vol 268 (6) ◽  
pp. R1464-R1471 ◽  
Author(s):  
P. Ruggeri ◽  
R. Ermirio ◽  
C. Molinari ◽  
F. R. Calaresu
Keyword(s):  
Nerve Stimulation ◽  
Sural Nerve ◽  
Tibial Nerve ◽  
Pressor Response ◽  
Cardiovascular Responses ◽  
Ventrolateral Medulla ◽  
Electrolytic Lesions ◽  
Cardiovascular Neurons ◽  
Muscle Nerve ◽  
Stimulation Of

Central neuronal circuits mediating reflex cardiovascular responses to skin and muscle nerve stimulation were studied in rats under urethan anesthesia. Responses of right rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM) cardiovascular neurons to stimulation of contralateral skin and muscle afferent fibers were investigated. Stimulation of the tibial (muscle) nerve excited 19 (86%) of 22 CVLM neurons and inhibited 18 (82%) of 22 RVLM neurons. Stimulation of the sural (skin) nerve excited 20 (91%) of the 22 RVLM neurons but did not affect the firing rate of any of the 22 CVLM neurons. Electrolytic lesions of the CVLM abolished the depressor responses induced by stimulation of the tibial nerve without affecting the pressor response caused by sural nerve stimulation. Similarly, reversible blockade of the CVLM by microinjection of gamma-amino-butyric acid or CoCl2 abolished the depressor response to stimulation of the tibial nerve without affecting the pressor response induced by sural nerve stimulation. These results suggest that vasodepressor responses to muscle nerve activation are mediated by a neuronal inhibitory pathway to the RVLM relayed through the CVLM.

scholarly journals elPBN neurons regulate rVLM activity through elPBN-rVLM projections during activation of cardiac sympathetic afferent nerves

2016 ◽  
Vol 311 (2) ◽  
pp. R410-R425 ◽  
Author(s):  
Zhi-Ling Guo ◽  
John C. Longhurst ◽  
Stephanie C. Tjen-A-Looi ◽  
Liang-Wu Fu
Keyword(s):  
Electrical Stimulation ◽  
Glutamate Transporter ◽  
Early Gene ◽  
Ventrolateral Medulla ◽  
Cardiovascular Reflexes ◽  
Homocysteic Acid ◽  
Central Processing ◽  
Afferent Nerves ◽  
Cardiovascular Neurons ◽  
Stimulation Of

The external lateral parabrachial nucleus (elPBN) within the pons and rostral ventrolateral medulla (rVLM) contributes to central processing of excitatory cardiovascular reflexes during stimulation of cardiac sympathetic afferent nerves (CSAN). However, the importance of elPBN cardiovascular neurons in regulation of rVLM activity during CSAN activation remains unclear. We hypothesized that CSAN stimulation excites the elPBN cardiovascular neurons and, in turn, increases rVLM activity through elPBN-rVLM projections. Compared with controls, in rats subjected to microinjection of retrograde tracer into the rVLM, the numbers of elPBN neurons double-labeled with c-Fos (an immediate early gene) and the tracer were increased after CSAN stimulation ( P < 0.05). The majority of these elPBN neurons contain vesicular glutamate transporter 3. In cats, epicardial bradykinin and electrical stimulation of CSAN increased the activity of elPBN cardiovascular neurons, which was attenuated ( n = 6, P < 0.05) after blockade of glutamate receptors with iontophoresis of kynurenic acid (Kyn, 25 mM). In separate cats, microinjection of Kyn (1.25 nmol/50 nl) into the elPBN reduced rVLM activity evoked by both bradykinin and electrical stimulation ( n = 5, P < 0.05). Excitation of the elPBN with microinjection of dl-homocysteic acid (2 nmol/50 nl) significantly increased basal and CSAN-evoked rVLM activity. However, the enhanced rVLM activity induced by dl-homocysteic acid injected into the elPBN was reversed following iontophoresis of Kyn into the rVLM ( n = 7, P < 0.05). These data suggest that cardiac sympathetic afferent stimulation activates cardiovascular neurons in the elPBN and rVLM sequentially through a monosynaptic (glutamatergic) excitatory elPBN-rVLM pathway.

Baroreceptor activation or glutamate coinjection facilitates depressor responses to ANF microinjection into NTS

1989 ◽  
Vol 257 (2) ◽  
pp. R405-R409
Author(s):  
D. J. McKitrick ◽  
F. R. Calaresu
Keyword(s):  
Electrical Stimulation ◽  
Significant Interaction ◽  
Cardiovascular Responses ◽  
Solitary Tract ◽  
Aortic Depressor Nerve ◽  
Male Wistar Rats ◽  
Threshold Doses ◽  
Baroreceptor Activation ◽  
Dorsal Medulla ◽  
Stimulation Of

As microinjection of atrial natriuretic factor (ANF) into the nucleus of the solitary tract (NTS) has been shown to elicit depressor responses [D. J. McKitrick and F. R. Calaresu. Am. J. Physiol. 255 (Regulatory Integrative Comp. Physiol. 24): R182-R187, 1988], we investigated the possibility that these responses might be facilitated either by electrical stimulation of arterial baroreceptor fibers in the aortic depressor nerve (ADN) or by simultaneous microinjection of L-glutamate (Glu) into the same sites in the NTS. Male Wistar rats (n = 51) were anesthetized with urethan (1.4 g/kg ip), artificially ventilated, and the dorsal medulla was exposed. The ADN was isolated, cut distally, and the central end was placed on bipolar stimulating electrodes. Threshold doses of 10(-7) M ANF microinjected into the NTS were combined with threshold electrical stimulation of the ADN (n = 37) or threshold doses of 0.13-0.5 M Glu (n = 14) microinjected into the NTS. There was a significant interaction between ANF microinjection and ADN stimulation in producing changes in mean arterial pressure (MAP) and heart rate [HR; P less than 0.05; -20.2 +/- 2.3 (SE) mmHg and -30.8 +/- 6.9 (SE) beats/min, respectively; n = 18]. There was also a significant interaction between ANF and Glu in producing changes in MAP and HR [P less than 0.05; -16.3 +/- 1.8 (SE) mmHg and -15.0 +/- 3.0 (SE) beats/min, respectively; n = 8]. These results indicate that ANF influences neurons in the NTS, which are also influenced by activation of arterial baroreceptors, and ANF and Glu interact in the NTS to produce facilitated cardiovascular responses.

Somatic and visceral inputs to neurons of the rostral ventrolateral medulla

1993 ◽  
Vol 265 (1) ◽  
pp. R35-R40 ◽  
Author(s):  
R. Ermirio ◽  
P. Ruggeri ◽  
C. Molinari ◽  
L. C. Weaver
Keyword(s):  
Sciatic Nerve ◽  
Nerve Stimulation ◽  
Rostral Ventrolateral Medulla ◽  
Ventrolateral Medulla ◽  
Renal Nerve ◽  
Afferent Stimulation ◽  
Cardiovascular Neurons ◽  
Sciatic Nerve Stimulation ◽  
Regulation Of Blood Pressure ◽  
Stimulation Of

Sympathoexcitatory neurons in the rostral ventrolateral medulla (RVLM) play an essential role in the generation of basal sympathetic tone and in the reflex regulation of blood pressure. In this study responses of RVLM "cardiovascular" neurons to somatic and visceral afferent stimulation were investigated. The activity of 34 RVLM neurons was recorded in urethan-anesthetized paralyzed and artificially ventilated rats. These neurons were identified as cardiovascular based on their baroreceptor sensitivity and their pulse-synchronous discharge. Electrical stimulation of the sciatic nerve excited 31 of the 34 RVLM units (91%). Renal nerve stimulation inhibited firing of 14 of 22 RVLM neurons tested (64%), not affecting the remaining 8 units. Stimulation of splenic nerves inhibited the discharge of 7 of 12 RVLM neurons tested (58%), whereas the remaining 5 units were not affected. All RVLM units responsive to visceral afferent stimulation were also responsive to sciatic nerve stimulation. These results indicate that RVLM cardiovascular neurons receive somatic and visceral inputs, suggesting an involvement of these units in the integration of homeostatic responses to changes in the internal and external environment.

Supramedullary inputs to cardiovascular neurons of rostral ventrolateral medulla in rats

1993 ◽  
Vol 265 (1) ◽  
pp. R111-R116 ◽  
Author(s):  
S. K. Agarwal ◽  
F. R. Calaresu
Keyword(s):  
Discharge Rate ◽  
Firing Frequency ◽  
Locus Ceruleus ◽  
Rostral Ventrolateral Medulla ◽  
Chemical Stimulation ◽  
Ventrolateral Medulla ◽  
Hypothalamic Area ◽  
Lateral Parabrachial Nucleus ◽  
Cardiovascular Neurons ◽  
Stimulation Of

Experiments were done to test the hypothesis that selective activation of cell bodies in different nuclei known to be involved in central cardiovascular control could excite or inhibit the discharge of neurons in the rostral ventrolateral medulla (RVLM). It is known that chemical stimulation of the lateral parabrachial nucleus (LPBN), locus ceruleus (LC), and lateral hypothalamic area (LHA) in anesthetized animals elicits increases (LPBN) or decreases (LC and LHA) in arterial pressure. We therefore recorded extracellularly spontaneous activity from RVLM units in urethan-anesthetized rats and monitored the changes in firing frequency of these neurons during chemical stimulation of one of LPBN, LC, and LHA. Thirty-two units were classified as cardiovascular neurons because their activity was inhibited by baroreceptor activation (1-3 micrograms phenylephrine iv) and displayed a cardiac cycle-related rhythmicity. Chemical stimulation with sodium glutamate of arterial pressor sites in the ipsilateral LPBN increased the firing frequency (40.3 +/- 1.3%) of 11 cardiovascular neurons. Activation of cell bodies in arterial depressor sites in the ipsilateral LC inhibited the firing rate (59.1 +/- 7.1%) of 10 cardiovascular neurons and excited 1 unit. Activation of cell bodies in arterial depressor sites in the ipsilateral LHA inhibited the discharge rate (25.4 +/- 4.7%) of six cardiovascular neurons, excited one unit, and did not alter the rate of the remaining three units. These results provide direct evidence for the existence of excitatory and inhibitory pathways from neurons located in the LPBN, LC, and LHA to cardiovascular neurons in the RVLM.

Effects of cannabinoid and vanilloid receptor agonists and their interaction on learning and memory in rats

2017 ◽  
Vol 95 (4) ◽  
pp. 382-387 ◽  
Author(s):  
Mariam Shiri ◽  
Alireza Komaki ◽  
Shahrbanoo Oryan ◽  
Masoumeh Taheri ◽  
Hamidreza Komaki ◽  
...  
Keyword(s):  
Learning And Memory ◽  
Cannabinoid Receptor ◽  
Vanilloid Receptor ◽  
Interactive Effects ◽  
Control Group ◽  
Acute Administration ◽  
Male Wistar Rats ◽  
Agonistic Effect ◽  
Stimulation Of

Despite previous findings on the effects of cannabinoid and vanilloid systems on learning and memory, the effects of the combined stimulation of these 2 systems on learning and memory have not been studied. Therefore, in this study, we tested the interactive effects of cannabinoid and vanilloid systems on learning and memory in rats by using passive avoidance learning (PAL) tests. Forty male Wistar rats were divided into the following 4 groups: (1) control (DMSO+saline), (2) WIN55,212–2, (3) capsaicin, and (4) WIN55,212–2 + capsaicin. On test day, capsaicin, a vanilloid receptor type 1 (TRPV1) agonist, or WIN55,212–2, a cannabinoid receptor (CB1/CB2) agonist, or both substances were injected intraperitoneally. Compared to the control group, the group treated with capsaicin (TRPV1 agonist) had better scores in the PAL acquisition and retention test, whereas treatment with WIN55,212–2 (CB1/CB2 agonist) decreased the test scores. Capsaicin partly reduced the effects of WIN55,212–2 on PAL and memory. We conclude that the acute administration of a TRPV1 agonist improves the rats’ cognitive performance in PAL tasks and that a vanilloid-related mechanism may underlie the agonistic effect of WIN55,212–2 on learning and memory.

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