Cholecystokinin and gastric distension activate oxytocinergic cells in rat hypothalamus.
Systemic administration of cholecystokinin octapeptide (CCK-8) prompts an abrupt increase in circulating levels of oxytocin (OXY) but not vasopressin (VP) in rats. The present study determined whether CCK-8 selectively stimulated OXY-secreting neurons in the hypothalamic supraoptic nucleus of pentobarbital-anesthetized male rats. Antidromically identified neurosecretory neurons were categorized into putative OXY- and VP-secreting cells on the basis of their firing patterns and response to peripheral baroreceptor activation. Of 36 OXY-secreting cells studied, 30 demonstrated a 50-200% increase in firing frequency within 2 min of administering CCK-8 by intravenous or intraperitoneal injection, whereas none of the eight VP-secreting neurons studied was activated. In related experiments, 4-10 ml of air were used to inflate an intragastric balloon in rats; 20 of 22 OXY-secreting neurons displayed an abrupt and readily reversible increase in firing frequency, whereas only 2 of 17 VP-secreting cells were activated. Gastric distension similarly elevated plasma OXY levels in unanesthetized rats with indwelling gastric cannulas. Together with previous findings that the effects of CCK-8 on OXY release were attenuated by gastric vagotomy, these observations clearly demonstrate the existence of a sensitive neural link between the stomach and the neurohypophysis in the rat.
Renaud
L P
LP
Neurosciences Unit, Montreal General Hospital, Quebec, Canada.
Tang
M
M
McCann
M J
MJ
Stricker
E M
EM
Verbalis
J G
JG
D000818:Animals; D007031:Hypothalamus / Q000187:drug effects*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010121:Oxytocin / Q000097:blood*; D010812:Physical Stimulation; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012844:Sincalide / Q000494:pharmacology*; D013270:Stomach / Q000294:innervation*; D013495:Supraoptic Nucleus / Q000187:drug effects / Q000378:metabolism; D014667:Vasopressins / Q000097:blood
D014667:Vasopressins; D010121:Oxytocin; D012844:Sincalide