The effects of subcutaneous administration of arginine-8-vasopressin on the electroencephalogram of conscious rats are mediated by peripheral vasopressin V1 receptors.

The effects of subcutaneous (s.c.) administration of arginine-8-vasopressin (AVP) were investigated on the electroencephalogram (EEG) of conscious rats. AVP (1 mcg/kg) had no effect on the EEG. However, AVP (5 and 10 mcg/kg) produced significant changes in the spectral power of the EEG in a manner that was consistent with increase in level of arousal. Analogs of AVP which are virtually devoid of vasopressin V1 receptor agonist activity, desglycinamide-9 arginine-8 vasopressin (10 mcg/kg, s.c.) and 1-deamino-8-D arginine-8 vasopressin (10 mcg/kg, s.c.), had no effect on the EEG. Pretreatment with 1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid)2(O-methyl)tyrosine arginine-8 vasopressin (10 mcg/kg), a vasopressin V1 receptor antagonist, abolished the effects of AVP (10 mcg/kg) on the EEG. As systemically administered AVP cannot cross the blood-brain barrier, the present results indicate that the effects of s.c. AVP on the EEG of conscious rats are mediated by peripheral vasopressin V1 receptors.