Exogenous vasopressin modulates activity of oxytocin neurons in homozygous Brattleboro rats.
We studied the effects of chronic replacement with arginine vasopressin (AVP) or 1-desamino-D-arginine vasopressin (DDAVP), as well as acute replacement with AVP or DDAVP, on the responsiveness of oxytocin (OT) neurons as indexed by plasma oxytocin-associated neurophysin concentration [( OT-RNP]) during acute salt loading in conscious, chronically catheterized homozygous Brattleboro (DI) rats. Salt loading was carried out on days 5 and 12 of AVP (3,000 ng/day) or DDAVP (50 ng/day) treatment or 60 min after intraperitoneal injection of 1 microgram AVP or 25 ng DDAVP. All vasopressin treatments did not significantly alter the basal [OT-RNP]. In response to infusion of 18% saline, there were corresponding significant increases in plasma osmolality (Posmol) and [OT-RNP] in all animals. The increases in [OT-RNP] in vasopressin-treated DI rats were markedly reduced compared with those observed earlier for untreated DI animals despite similar rises in Posmol. The slopes of the relationship between delta [OT-RNP] and delta Posmol were 9.0 and 9.8 fmol X ml-1 X mosmol-1 X kg for chronically AVP-treated DI rats, 8.9, and 8.8 fmol X ml-1 X mosmol-1 X kg for chronically DDAVP-treated DI animals, 10.7 fmol X ml-1 X mosmol-1 X kg for acutely AVP-treated DI rats, and 8.3 fmol X ml-1 X mosmol-1 X kg for acutely DDAVP-treated animals compared with that of 34.9 fmol X ml-1 X mosmol-1 X kg for untreated DI rats.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001769:Blood; D003894:Deamino Arginine Vasopressin / Q000494:pharmacology; D003919:Diabetes Insipidus / Q000503:physiopathology*; D008297:Male; D009474:Neurons / Q000502:physiology*; D009481:Neurophysins / Q000097:blood; D009994:Osmolar Concentration; D010121:Oxytocin / Q000378:metabolism*; D010904:Pituitary Gland, Posterior / Q000503:physiopathology; D051381:Rats; D011910:Rats, Brattleboro; D012462:Saline Solution, Hypertonic; D012965:Sodium Chloride / Q000494:pharmacology; D014667:Vasopressins / Q000494:pharmacology*
D009481:Neurophysins; D012462:Saline Solution, Hypertonic; D014667:Vasopressins; D012965:Sodium Chloride; D010121:Oxytocin; D003894:Deamino Arginine Vasopressin