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

Summary 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.