Behavioral effects of intraventricularly administered vasopressin and vasopressin fragments

Vasopressin is involved in memory processes. A single subcutaneous injection of arginine-8-vasopressin (AVP) increases resistance to extinction of a pole jumping avoidance response. This effect can also be achieved after a single intraventricular administration of much lower amounts than after systemic injection. The covalent ring of AVP, pressinamide (PA), is also highly active following intraventricular administration while the C-terminal part prolyl-arginyl-glycinamide (PAG) is less active. These results indicate that the covalent ring of vasopressin contains the essential requirements for the behavioral effect of this neurohormone. A second activity site however may be present in the C-terminal portion of the molecule.