Central administration of arginine vasotocin: effects on exploratory behavior in the rat.

Synthetic arginine vasotocin (AVT) was infused into rat brains either by intraventricular administration or by local infusion on the pineal body. Subsequently, exploratory behavior was analyzed in a hole board. The behavioral effects induced by this peptide were dependent on the time of day, i. e. the light or the dark phase. High intraventricular doses (0.4 microgram) administered during the light phase altered exploratory activity such that the number of hole visits was increased, while the duration of each visit was decreased; lower doses produced no effect. In contrast, during the dark phase peripineal infusion of AVT (10(-4) pg) attenuated the number of hole visits and increased the mean duration of the visits. The strongest effects were obtained with peripineal applications during the dark phase. This treatment also resulted in significantly lowered levels of pineal melatonin.