Possible evidence of angiotensin II and endogenous opioid modulation of novelty-induced rearing in the rat.

Rats treated with captopril (CAP, 10mg/kg i.p.) naltrexone (Nalx 0.1 mg/kg i.p) and saralasine (100 micrograms/kg i.p) displayed significantly less novelty-induced rearing (NIR) compared to saline injected animals. Naltrexone potentiated the inhibitory effect of CAP on NIR. Pretreatment with NALX did not alter SARA-induced decrease in NIR. It is suggested that the endogenous release of AII and/or opioids somehow modulate basal rearing activity.