BARREL ROTATION INDUCED BY CENTRAL ARGININE(8)-VASOPRESSIN TREATMENT - INVOLVEMENT OF NEUROHYPOPHYSEAL PEPTIDE RECEPTORS

Two series of experiments were done to investigate the mechanism underlying arginine(8)-vasopressin (AVP)-induced barrel rotation in rats. In the first series, the effect of intracerebroventricular (ICV) administration of various neurohypophyseal hormone antagonists on AVP-induced barrel rotation was studied. The more vasopressin was given, the more the rats exhibited barrel rotation. ICV pretreatment with a V-1 vasopressin receptor antagonist, d(CH2)(5)[Tyr(Me)(2)]AVP, prevented barrel rotation, while similar treatment with a V-2-antagonist, d(CH2)(5)[dIle(2)Ile(4)]AVP, did not affect vasopressin-induced barrel rotation. However, Des-Gly,NH(2)d(CH2)(5)[Tyr)Me(2))Thr(4)Orn(8)]-vasotocin, a specific oxytocin antagonist, potentiated the effect of AVP on barrel rotation. The second experiment was performed in rats equipped with a telemetry system to measure heart rate (HR), core temperature (CT), and gross locomotor activity. Also, in this experiment the incidence of AVP-induced barrel rotation was dosedependent, as was the number of rats that died. Barrel rotation was accompanied by a significant decrease in CT and HR, while rats that did not develop hypothermia did not show barrel rotation. These results suggest that a V-1 receptor is involved in barrel rotation. Since AVP-induced hypothermia is also mediated by a V-1 receptor, it is postulated that hypothermia is a prerequisite for barrel rotation to occur. Further experiments are needed to substantiate this hypothesis.