The inhibitory effect of the ventrolateral periaqueductal grey matter on neurones in the rostral ventrolateral medulla involves a relay in the medullary raphe nuclei

1993 ◽  
Vol 94 (2) ◽  
Author(s):  
W.H. Wang ◽  
T.A. Lovick
Keyword(s):  
Grey Matter ◽  
Inhibitory Effect ◽  
Rostral Ventrolateral Medulla ◽  
Raphe Nuclei ◽  
Ventrolateral Medulla ◽  
Periaqueductal Grey ◽  
Periaqueductal Grey Matter ◽  
Medullary Raphe ◽  
Raphé Nuclei

GABA-mediated inhibition of sympathoexcitatory neurons by midline medullary stimulation

1988 ◽  
Vol 255 (4) ◽  
pp. R605-R615 ◽  
Author(s):  
R. B. McCall
Keyword(s):  
Electrical Stimulation ◽  
Rostral Ventrolateral Medulla ◽  
Raphe Nuclei ◽  
Ventrolateral Medulla ◽  
Conduction Time ◽  
Gamma Aminobutyric Acid ◽  
Medullary Raphe ◽  
Raphé Nuclei ◽  
Inferior Cardiac Nerve ◽  
Stimulation Of

The present investigation determined whether the effects of electrical stimulation of depressor sites in midline medullary raphe nuclei were a result of inhibition of sympathoexcitatory medullospinal neurons in the rostral ventrolateral medulla of anesthetized cats. Electrical stimulation of the raphe inhibited inferior cardiac sympathetic activity. Microinjections of glutamate mimicked the effects of electrical stimulation. Electrical stimulation inhibited sympathoexcitatory neurons in the rostral ventrolateral medulla. The onset of the sympathoinhibition recorded from the inferior cardiac nerve (72 ms) was equal to the sum of the onset latency of the sympathoexcitatory response elicited from the rostral ventrolateral medulla (49 ms) plus the conduction time in the raphe to rostral ventrolateral sympathoinhibitory pathway (23 ms). Raphe stimulation excited a second set of neurons in the rostral ventrolateral medulla with an onset of 21 ms. Microiontophoretically applied bicuculline increased the discharge of sympathoexcitatory neurons and blocked the raphe-evoked inhibition. Iontophoretic glutamate excited sympathoexcitatory neurons but failed to antagonize raphe-elicited inhibition. These data suggest that neuronal elements in medullary raphe nuclei tonically inhibit sympathoexcitatory medullospinal neurons in the rostral ventrolateral medulla by activating closely adjacent gamma-aminobutyric acid (GABA) interneurons.

Powerful depressor and sympathoinhibitory effects evoked from neurons in the caudal raphe pallidus and obscurus

1995 ◽  
Vol 268 (5) ◽  
pp. R1295-R1302 ◽  
Author(s):  
M. J. Coleman ◽  
R. A. Dampney
Keyword(s):  
Arterial Pressure ◽  
Sympathetic Activity ◽  
Raphe Nuclei ◽  
Ventrolateral Medulla ◽  
Gamma Aminobutyric Acid ◽  
Medullary Raphe ◽  
Dose Dependent Decrease ◽  
Raphé Nuclei ◽  
Raphe Pallidus ◽  
Dose Dependent

Microinjection of glutamate into sites within the medullary raphe nuclei (pallidus and obscurus) at levels caudal to the obex resulted in a dose-dependent decrease in mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA), and heart rate in anesthetized rabbits. The depressor and sympathoinhibitory responses were similar in magnitude to those elicited from the previously described depressor region in the caudal ventrolateral medulla (CVLM) but had a shorter duration, in both intact and barodenervated animals. The bradycardia was not altered by barodenervation but was reduced after administration of propranolol or atropine and abolished after administration of both drugs. The neuroinhibitory compounds gamma-aminobutyric acid or muscimol had no effect on MAP or RSNA when injected into the caudal medullary raphe nuclei but evoked a pressor and sympathoexcitatory response when injected into the CVLM. The results indicate that neurons within the caudal raphe pallidus and obscurus can powerfully inhibit sympathetic activity, but unlike sympathoinhibitory neurons in the CVLM, they are not tonically active and are not capable of producing sustained changes in arterial pressure and sympathetic activity.

Lateral tegmental field neurons of cat medulla: a potential source of basal sympathetic nerve discharge

1985 ◽  
Vol 54 (6) ◽  
pp. 1498-1512 ◽  
Author(s):  
G. L. Gebber ◽  
S. M. Barman
Keyword(s):  
Slow Wave ◽  
Sympathetic Nerve ◽  
Baroreceptor Reflex ◽  
Raphe Nuclei ◽  
Ventrolateral Medulla ◽  
Related Activity ◽  
Medullary Raphe ◽  
Reflex Activation ◽  
Raphé Nuclei ◽  
Nerve Discharge

A study was made of 170 neurons of the lateral tegmental field (LTF) of the cat medulla with spontaneous activity temporally related to the 2- to 6-Hz slow wave in inferior cardiac postganglionic sympathetic nerve discharge (as demonstrated with spike-triggered averaging). LTF neurons were excited by the iontophoresis of L-glutamate, and an inflection on the rising phase of their action potentials was observed. Thus, the site of extracellular unit recording presumably was in the region of the cell body. The lag between LTF unit spike occurrence and the peak of the 2- to 6-Hz slow wave in sympathetic nerve discharge (SND) was unchanged when blood pressure and, thus, baroreceptor nerve activity were lowered to a level at which the phase relationship between the slow wave and the cardiac cycle was disrupted. Thus, the discharges of LTF neurons apparently were more closely associated with those of elements of "efferent" brain stem networks controlling SND than with those of interneurons in the afferent limb of the baroreceptor reflex arc. LTF neurons with sympathetic nerve- and cardiac-related activity were classified into three types depending on their responses to elevated carotid sinus pressure (i.e., baroreceptor reflex activation). Of the 82 neurons tested, 33 were inhibited, 16 were excited, and 33 were unaffected by baroreceptor reflex activation. Using data collected in this and previous studies from our laboratory, we compared the firing times of neurons in the LTF, rostral ventrolateral medulla, and medullary raphe nuclei relative to the peak of the sympathetic nerve slow wave. LTF neurons that were inhibited by baroreceptor reflex activation are presumed to subserve a sympathoexcitatory function. These neurons fired significantly earlier during the sympathetic nerve slow wave than their counterparts in the rostral ventrolateral medulla and medullary raphe nuclei. LTF neurons classified as sympathoinhibitory (i.e., excited by baroreceptor reflex activation) fired significantly earlier than their counterparts in the medullary raphe nuclei. These data raise the possibility that LTF neurons are closer (at least in a temporal sense) to the region of origin of the 2- to 6-Hz component of SND than are ventrolateral medullary and raphe neurons. The firing times of sympathoexcitatory and sympathoinhibitory LTF neurons were not significantly different. These data are discussed relative to potential mechanisms involved in generating SND. Microstimulation of the second thoracic spinal segment was used to determine whether the axons of LTF neurons with sympathetic nerve-related activity projected to this level.(ABSTRACT TRUNCATED AT 400 WORDS)

Neglected woman with hyperemesis gravidarum leading to Wernicke encephalopathy

2020 ◽  
Vol 13 (12) ◽  
pp. e238545
Author(s):  
Papa Dasari ◽  
Smitha Priyadarshini
Keyword(s):  
Grey Matter ◽  
Hyperemesis Gravidarum ◽  
Intravenous Fluids ◽  
State Of Health ◽  
Wernicke Encephalopathy ◽  
Periaqueductal Grey ◽  
Mri Brain ◽  
Good State ◽  
Periaqueductal Grey Matter ◽  
History Of

A teenage primigravida at 13 weeks of gestation presented with hyperemesis gravidarum of 45 days and a history of giddiness and inability to walk due to involuntary movements of limbs and eyes since 2 days. She was treated with intravenous fluids, thiamine and antiemetics. MRI brain showed hyperintensities in bilateral dorsomedial thalami, periaqueductal grey matter in T2-weighted and FLAIR images. A diagnosis of Wernicke encephalopathy was made and she was managed in intensive care unit and received injection thiamine as per the guidelines and her weakness and ataxia improved over 3 weeks and she was discharged at 17 weeks of pregnancy in good state of health.

Origin of respiratory activities in the medullary raphe nuclei of rats

1998 ◽  
Vol 31 ◽  
pp. S163
Author(s):  
Masae Hosogai ◽  
Yasuaki Kawai
Keyword(s):  
Raphe Nuclei ◽  
Medullary Raphe ◽  
Raphé Nuclei
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