| Abstract: | Two experiments investigated the mechanism for changes in measures of behavioral arousal inhibition in rats following administration of atropine. In Experiment 1, 40-day-old rats were given administrations of atropine sulfate, the α-, β-adrenergic blocker labetalol, or both. The drugs, either alone or in combination, increased transport response intensity, whereas both together increased dorsal immobility durations. In Experiment 2, rats were given atropine, the β-adrenergic antagonist propranolol, the α-adrenergic antagonist phentolamine, or a combination of two of the drugs. Propranolol blocked atropine-induced increases in transport response, and phentolamine was without effect. Phentolamine, when combined with atropine, increased dorsal immobility durations. Results are discussed with respect to aspects common to both transport response and dorsal immobility. |
