Selective inhibition of magnocellular vasopressin neurons by hypoosmolality: effect on histamine- and stress-induced secretion of adrenocorticotropin and prolactin.
We investigated the effect of selective inhibition of magnocellular arginine vasopressin (AVP) and oxytocin neurons on histamine (HA)- and restraint-stress-induced adrenocorticotropin (ACTH) and prolactin (PRL) secretion in conscious male rats. The inhibition of magnocellular neurons was obtained by inducing chronic hypoosmolality via continuous exposure of the rats to the AVP V2 receptor agonist 1-deamino(8-D-arginine)vasopressin (DDAVP) which was released from osmotic pumps implanted subcutaneously. In DDAVP-treated rats, plasma osmolality and sodium concentration were 273 mosm/l and 130 mmol/l, respectively. In control rats, the corresponding values were 291 mosm/l and 139 mmol/l. HA (270 nmol) administered intracerebroventricularly or 5 min of restraint stress stimulated ACTH and PRL secretion 4- to 11-fold in normoosmolar rats. In hypoosmolar rats, the HA-induced ACTH response was inhibited more than 40% whereas the restraint-stress-induced ACTH response was unaffected. Conversely, the PRL response to HA in hypoosmolar rats was unaffected whereas the PRL response to restraint stress was inhibited by 40%. In summary, chronic hypoosmolality inhibits HA-induced ACTH and restraint-stress-induced PRL secretion indicating involvement of magnocellular AVP in these responses.
Kjaer
A
A
Department of Medical Physiology, Panum Institute, University of Copenhagen, Denmark. kjaer@mfi.ku.dk
Knigge
U
U
Jørgensen
H
H
Warberg
J
J
D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000502:physiology*; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D009994:Osmolar Concentration; D010121:Oxytocin / Q000502:physiology; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012076:Renal Agents / Q000494:pharmacology; D012149:Restraint, Physical; D012636:Secretory Rate / Q000187:drug effects; D013312:Stress, Physiological / Q000503:physiopathology*; D013377:Substantia Innominata / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D012076:Renal Agents; D001127:Arginine Vasopressin; D010121:Oxytocin; D006632:Histamine; D000324:Adrenocorticotropic Hormone; D011388:Prolactin; D003894:Deamino Arginine Vasopressin