Evidence for a specific role of vasopressin in sustaining pituitary-adrenocortical stress response in the rat.
In the adult male Wistar rat a 2-fold 2-min restraint stress exposure, repeated 15 min apart, activated the adrenocortical secretion more than a single one would have. However, in rats with a pharmacological block of the endogenous CRF release, exogenous CRH (0.3 micrograms/kg iv), administered 15 min after a first similar dose, was unable to stimulate pituitary-adrenocortical activity above the level attained with the first peptide injection. On the contrary, in the same conditions exogenous arginine vasopressin (AVP) (0.3 micrograms/kg iv) administered 15 min after CRH, was able to further stimulate pituitary-adrenocortical activity. Using the same experimental procedure, oxytocin (0.3 micrograms/kg iv) was found to be totally inactive. The physiological import of these findings was investigated in the Brattleboro rat, genetically lacking in endogenous AVP, in which, unlike the control Long-Evans strain, the 2-fold stress exposure did not cause an increase in plasma corticosterone concentration greater than that of a single exposure. These results suggest that endogenous AVP is essential in sustaining adrenocortical activation in circumstances in which pituitary refractoriness towards CRH stimulation intervenes.
Scaccianoce
S
S
Institute of Pharmacology, Second Chair, Medical Faculty, University La Sapienza, Rome, Italy.
Muscolo
L A
LA
Cigliana
G
G
Navarra
D
D
Nicolai
R
R
Angelucci
L
L
D000758:Anesthesia; D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D008297:Male; D009994:Osmolar Concentration; D010121:Oxytocin / Q000494:pharmacology; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D051381:Rats; D011910:Rats, Brattleboro; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000097:blood / Q000503:physiopathology*; D014667:Vasopressins / Q000502:physiology*
D014667:Vasopressins; D001127:Arginine Vasopressin; D010121:Oxytocin; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone