Dissociation of the behavioural and endocrine effects of lysine vasopressin by tryptic digestion

1. Lysine vasopressin induces resistance to extinction of active avoidance behaviour (De Wied, 1971).2. Digestion of lysine vasopressin with trypsin almost completely destroys the pressor-, antidiuretic-, oxytocic- and corticotrophin-releasing factor activities of lysine vasopressin, but does not materially influence its effect on the maintenance of an avoidance response.