The role of alpha-2 adrenoceptors in the regulation of oxytocin neurones in the suckled rat.
The role of alpha-2 adrenoceptors in the milk-ejection reflex was investigated by making electrophysiological recordings from oxytocin neurones in the supraoptic nucleus of urethane-anaesthetised rats. Systemic administration of the alpha-2 adrenoceptor antagonist. Idazoxan (0.5 mg/kg, i.v.), temporarily suppressed OT cell bursting activity, while having no consistent action on basal neuronal activity. Clonidine (25 micrograms/kg, i.v.) caused an immediate increase in the frequency and amplitude of oxytocin cell bursting, coincident with a fall in basal activity. A higher dose of clonidine (50 micrograms/kg, i.v.), inhibited both bursting and basal activity. These results indicate that alpha-2 adrenoceptors are essential for the normal functioning of the milk-ejection reflex and may be involved in the facilitatory and inhibitory regulation of suckling-evoked bursting in oxytocin neurones.
Bailey
A
A
Department of Anatomy, School of Medical Sciences, University of Bristol, UK.
Clarke
G
G
Wakerley
J
J
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000833:Animals, Suckling / Q000502:physiology; D003000:Clonidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D019329:Idazoxan / Q000494:pharmacology; D007774:Lactation / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010121:Oxytocin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D013495:Supraoptic Nucleus / Q000166:cytology / Q000187:drug effects / Q000502:physiology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011942:Receptors, Adrenergic, alpha; D010121:Oxytocin; D003000:Clonidine; D019329:Idazoxan