Activation of 5-ht1a Receptors in Rostral Medullary Raphé Inhibits Cutaneous Vasoconstriction Elicited by Cold Exposure in Rabbits.
From: Department of Human Physiology, Centre for Neuroscience, Flinders University, Bedford Park, South Australia 5042, Australia. yoichiro.otsuka@flinders.edu.au
Brain research
- Publish Date: Feb 2006
- ISSN: 0006-8993
- Volume: 1073-1074
- Issue:
- Pages: 252-61
- Medium: Print
- Language: English
- Citation (JAMA): Ootsuka Youichirou, Blessing William W, et al. Activation of 5-ht1a Receptors in Rostral Medullary Raphé Inhibits Cutaneous Vasoconstriction Elicited by Cold Exposure in Rabbits.. Brain Res. Feb 2006;1073-1074:252-61
Abstract
In both conscious and anesthetized rabbits, we determined whether microinjection of a 5-hydroxytryptamine (5-HT) 1A receptor agonist 8-hydroxy-2-(di-n-propylaminio) tetralin (8-OH-DPAT) into the medullary raphé/parapyramidal region inhibits thermoregulatory vasoconstriction and whether microinjection of a 5-HT1A receptor antagonist (N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-(2-pyridinyl) cyclohexanecarboxamide trihydrochloride) (WAY-100635) into the raphé reverses the cutaneous vasomotor changes induced by intravenous administration of 8-OH-DPAT. In conscious rabbits with measuring ear pinna blood flow, after microinjection of 8-OH-DPAT (3-5 nmol in 300-500 nl) into the raphé, transferring the animal from a warm cage (25-28 degrees C) to a cold cage (5-10 degrees C) did not reduce the ear pinna flow (from 57 +/- 7 cm/s to 59 +/- 3 cm/s, P > 0.05, n = 5), unlike Ringer-treated animals. Microinjection of WAY-100635 (5 nmol in 500 nl) into the raphé reversed ear pinna flow changes induced by intravenous administration of 8-OH-DPAT (0.1 mg/kg, i.v.). In anesthetized rabbits with measuring postganglionic ear pinna sympathetic nerve activity, microinjection of 8-OH-DPAT (1-2 nmol in 100-200 nl) into the raphé reduced resting ear pinna sympathetic nerve activity to 14 +/- 4% of pre-injection level (P < 0.01, n = 12) and attenuated increases in ear pinna sympathetic nerve activity normally elicited by cooling the animal’s trunk. WAY-100635 (2 nmol into 200 nl) into the raphé reversed inhibition of ear pinna sympathetic nerve activity elicited by 8-OH-DPAT (0.1 mg/kg, i.v.). The activation of 5-HT1A receptors expressed on the medullary raphé neurons results in reversal of cold-elicited cutaneous vasoconstriction possibly through inhibition of sympathetic premotor neurons that innervate sympathetic preganglionic neurons controlling cutaneous vasomotion.
Mesh Headings (Keywords): 8-Hydroxy-2-(di-n-propylamino)tetralin, Analysis of Variance, Animals, Behavior, Animal, Blood Pressure, Body Temperature, Cold, Male, Piperazines, Pyridines, Rabbits, Raphe Nuclei, Receptor, Serotonin, 5-HT1A, Serotonin Agonists, Serotonin Antagonists, Skin, Sympathetic Nervous System, Ultrasonography, Doppler, Color, Vasoconstriction, Wakefulness
Check for Full Text / PubMed Unique Identifier (PMID): 16455061
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