AJP - Endocrinology and Metabolism, Vol 251, Issue 5 556-E562, Copyright © 1986 by American Physiological Society
Exogenous vasopressin modulates activity of oxytocin neurons in homozygous Brattleboro rats
S. W. Cheng and W. G. North
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)
