Short-term behavioral effects of posterior pituitary peptides in mice.

The acute behavioral effects of some neurohypophyseal hormones after intracerebroventricular injection in mice were examined. The effects, consisting mainly of a dose-dependent stimulation of certain behaviors, were demonstrated in three different behavioral tests. The type of the induced behaviors was dependent on the experimental conditions: If the mice were placed into a cage after the injection of the peptides, excessive scratching and grooming behaviors were induced. If they were exposed to stressful environmental influences, however, escape-directed activity was markedly stimulated with only minimal elevation of scratching and grooming behaviors. Very low doses down to less than 1 nanogram per mouse were effective. The effects can be observed after central, but not after peripheral application of the peptides and are mediated by a mechanism that displays some degree of specificity. An activity unit for the behavior-altering potency of the peptides was defined. A role of neurohypophyseal hormones or related peptides in the regulation of motivation and behavioral arousal is suggested.