Pinealectomy blocks modulation of active avoidance by central vasopressin application in rats

The inter-relationship between central vasopressin and the pineal gland in the modulation of active avoidance behavior was investigated. In sham-operated (SO) rats, intracerebroventricular (i.c.v) application of 10 ng arginine vasopressin (AVP) after both the last acquisition and the first extinction trials prolonged the extinction of the active avoidance response; application of 50 ng of the V1 antagonist, d(CH2)5Tyr(Me)AVP (AAVP) was without effect in both experiments. In contrast to the SO in pinealectomized (PX) rats neither AVP nor AAVP influenced the extinction of the avoidance response. Intraseptal infusion of 200 pg AVP or 5 ng AAVP either after the last acquisition or the first extinction trial was without effect in both SO and PX rats. Comparison of the acquisition trials revealed no differences between SO and PX rats.