Effects of substance P and thyrotropin-releasing hormone on sympathetic preganglionic neurones in the upper thoracic intermediolateral nucleus of the cat

When applied by iontophoresis onto single sympathetic preganglionic neurones in the intermediolateral nucleus of spinal segments T1–T3 in the cat, substance P and thyrotropin-releasing hormone (TRH) each had a weak excitatory effect. Two-thirds of the neurones studied were excited by substance P while one-fifth were excited by TRH. The time courses of the responses to substance P and to TRH were similar, and consisted of an increase in the rate of discharge with a latency of approximately 30 s from the onset of application. They were also prolonged (30–320 s) in afterdischarge following termination of application. These results indicate that substance P and TRH exert excitatory effects on single sympathetic preganglionic neurones, and support the possibility that they may be chemical mediators of synaptic transmission in the intermediolateral nucleus.

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Adrenal versus nonadrenal sympathetic preganglionic neurones in the lower thoracic intermediolateral nucleus of the cat: effects of serotonin, substance P, and thyrotropin-releasing hormone

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y90-166 ◽

1990 ◽

Vol 68 (8) ◽

pp. 1108-1118 ◽

Cited By ~ 23

Author(s):

S. B. Backman ◽

H. Sequeira-Martinho ◽

J. L. Henry

Keyword(s):

Substance P ◽

Gradual Increase ◽

Thyrotropin Releasing Hormone ◽

Releasing Hormone ◽

Iontophoretic Application ◽

Preganglionic Neurone ◽

Spinal Segments ◽

Excitatory Responses ◽

Intermediolateral Nucleus ◽

Chemical Mediators

Adrenal and nonadrenal sympathetic preganglionic neurones (SPNs) in the intermediolateral nucleus of spinal segments T8–T10 in the cat were compared according to their responses to iontophoretic application of serotonin, substance P, and thyrotropin-releasing hormone (TRH). Responses of both types of SPN to iontophoretic application of serotonin were characterized by an increase in the rate of discharge that was slow in onset (mean ± SD = 36 ± 21 s) and prolonged in afterdischarge (115 ± 70 s) following termination of application. Depression was never observed and responses were similar whether using serotonin at a pH of 3.3 or 4.5, suggesting that the absence of a depressant effect cannot be accounted for by pH, as has been reported with cortical neurones. Iontophoretic application of methysergide resulted in a decrease in the rate of discharge of both types of SPN and blocked the excitatory responses to serotonin. Adrenal and nonadrenal SPNs were excited by iontophoretic application of substance P. Responses of both types of SPN were similar and were characterized by a gradual increase in the rate of discharge that was slow in onset (42 ± 27 s) and prolonged in afterdischarge (96 ± 42 s). Finally, adrenal and nonadrenal SPNs were also weakly excited by iontophoretic application of TRH. These responses were slow in onset (48 ± 27 s) and prolonged in afterdischarge (78 ± 35 s). These data indicate that serotonin, substance P, and TRH exert excitatory effects on functionally dissimilar sympathetic preganglionic neurones and support the possibility that they may be chemical mediators of synaptic transmission in the intermediolaterai nucleus. In addition, these data may be interpreted to support the notion that serotonin, substance P, and TRH are involved in global activation of the sympathetic nervous system.Key words: sympathetic preganglionic neurone, spinal cord, lateral horn, iontophoresis, serotonin, substance P, thyrotropin-releasing hormone.

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Action of 5-Hydroxytryptamine, Substance P, Thyrotropin-Releasing Hormone and Clonidine on Motoneurone Excitability

Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques ◽

10.1017/s0317167100038002 ◽

1987 ◽

Vol 14 (S3) ◽

pp. 506-509 ◽

Cited By ~ 22

Author(s):

Paul J. Bédard ◽

L.E. Tremblay ◽

H. Barbeau ◽

M. Filion ◽

R. Maheux ◽

...

Keyword(s):

Substance P ◽

Pilot Trial ◽

Thyrotropin Releasing Hormone ◽

Excitatory Effect ◽

Releasing Hormone ◽

Hindlimb Muscles ◽

Spinal Lesion ◽

Subsequent Response ◽

Strong Excitation ◽

Integrated Emg

ABSTRACT:We have investigated the influence on the excitability of lumbar motoneurons of 5-hydroxytryptamine (5-HT), substance P and thyrotropin releasing hormone (TRH), three substances which coexist in the same bulbospinal descending pathway and end in large part around motoneurons. We have also studied the effect of clonidine, an alpha 2 noradrenergic agonist. This was done in spinalized rats (T5) treated three weeks before with 5-7-dihydroxytryptamine. Under those circumstances 5-HTP (LP.), 5-HT (intrathecally) TRH (LP. or I.T.) and substance P (I.T.) all elicited a strong excitation of motoneurons as measured by integrated EMG of the hindlimb muscles. Substance P reduced by almost half the subsequent response to 5-HTP, 1 hour and 24 hours later. TRH given acutely did not modify the response to 5-HTP but given chronically for twenty one days by means of Alzet minipump, markedly increased the response to 5-HTP. Clonidine by itself decreased the excitability of motoneurons and antagonized the excitatory effect of 5-HTP and TRH. In a pilot trial, cyproheptadine, a 5-HT antagonist was shown to decrease the manifestations of spasticity in patients with a partial spinal lesion. Clonidine also appears to be of potential use in the treatment of spasticity.

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Enkephalin-, thyrotropin-releasing hormone- and substance P-immunoreactive axonal innervation of the ventrolateral dendritic bundle in the cat sacral spinal cord: An ultrastructural study

Journal of Chemical Neuroanatomy ◽

10.1016/0891-0618(94)90013-2 ◽

1994 ◽

Vol 7 (4) ◽

pp. 203-215 ◽

Cited By ~ 5

Author(s):

V. Ramírez-León ◽

T. Hökfelt ◽

A.C. Cuello ◽

T.J. Visser ◽

B. Ulfhake

Keyword(s):

Spinal Cord ◽

Substance P ◽

Ultrastructural Study ◽

Thyrotropin Releasing Hormone ◽

Releasing Hormone ◽

Dendritic Bundle ◽

Sacral Spinal Cord

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Thyrotropin-releasing hormone: an inhibitory regulatory peptide of feline lower esophageal sphincter

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.1993.264.3.g522 ◽

1993 ◽

Vol 264 (3) ◽

pp. G522-G527 ◽

Cited By ~ 2

Author(s):

H. P. Parkman ◽

J. C. Reynolds ◽

C. P. Ogorek ◽

M. S. Kreider

Keyword(s):

Gastrointestinal Tract ◽

Substance P ◽

Lower Esophageal Sphincter ◽

Muscle Layer ◽

Left Gastric Artery ◽

Thyrotropin Releasing Hormone ◽

Relative Distribution ◽

Releasing Hormone ◽

Exogenous Substance ◽

Esophageal Sphincter

The functional role of thyrotropin-releasing hormone (TRH) at the lower esophageal sphincter (LES) was examined in the cat. The specific aims of this study were to determine: 1) the relative distribution of TRH throughout the feline gastrointestinal tract and 2) the effect of TRH on LES basal pressures and its response to exogenously induced contractions. TRH concentrations were determined by radioimmunoassay in tissue extracts from 12 sites. The mean concentration of TRH at the manometrically determined LES was 240 +/- 85 pg/g wet wt tissue, and the maximal concentration was just distal to the LES (659 +/- 189 pg/g wet wt). TRH concentration was higher in the mucosa than the underlying muscle layer of the fundus, antrum, duodenum, and ileum. In physiological studies, TRH given selectively via the left gastric artery had no effect on basal LES or esophageal pressures. TRH (2.8 x 10(-8) mol/kg) decreased the LES response to the D50 of substance P by 47.2% (34.8 +/- 3.1 to 18.4 +/- 2.9 mmHg, P < 0.01). In the presence of tetrodotoxin, TRH gave a similar inhibition of substance P-induced contractions (53.5%). TRH also decreased bombesin-induced contractions by 47.5% (29.6 +/- 6.0 to 15.8 +/- 3.9 mmHg, P < 0.025). TRH, however, had no effect on bethanechol-induced contractions. We conclude that 1) TRH is present throughout the gastrointestinal tract, with highest concentrations in the region distal to the LES; 2) TRH has no effect on basal LES tone; and 3) TRH inhibits the LES response to endogenously released and exogenous substance P but not the LES response to bethanechol.(ABSTRACT TRUNCATED AT 250 WORDS)

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