mu- and K-opiate receptor agonists reduce plasma neurohypophysial hormone concentrations in water-deprived and normally hydrated rats.
1. The effects of mu- and K-opiate receptor agonists on plasma concentrations of immunoreactive (ir) oxytocin (OXY) and arginine vasopressin (AVP) in normally hydrated and water-deprived rats were studied. 2. Water-deprivation for 36 h elevated both plasma ir-OXY and ir-AVP concentrations of Long-Evans rats. These elevated levels were lowered in a dose-dependent manner after subcutaneous administration of bremazocine (3-10 micrograms/kg), M320 (10-100 micrograms/kg) or morphine (0.1-10 mg/kg). Comparable reductions of plasma concentrations of ir-AVP and ir-OXY were observed. 3. Plasma concentrations of ir-OXY and ir-AVP of normally hydrated Long-Evans rats were lower after subcutaneous administration of bremazocine (10 micrograms/kg), M320 (10 micrograms/kg) and morphine (1.0 mg/kg). 4. These data suggest that both mu- and K-opiate receptor agonists inhibit both OXY and AVP release from the neurohypophysis of rats.
Evans
R G
RG
Department of Pharmacology, Monash University, Clayton, Victoria, Australia.
Olley
J E
JE
Rice
G E
GE
Abrahams
J M
JM
D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D007279:Injections, Subcutaneous; D008297:Male; D009294:Narcotics / Q000494:pharmacology; D010121:Oxytocin / Q000097:blood; D010909:Pituitary Hormones, Posterior / Q000097:blood*; D011863:Radioimmunoassay; D051381:Rats; D011957:Receptors, Opioid / Q000502:physiology*; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D014868:Water Deprivation / Q000502:physiology*
D009294:Narcotics; D010909:Pituitary Hormones, Posterior; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D001127:Arginine Vasopressin; D010121:Oxytocin