Cholinergic involvement in the modulation of oxotremorine-tremor in mice by propranolol.

Propranolol in low doses antagonized and in higher doses facilitated oxotremorine-induced tremor (Oxo-tremor) in mice. Atropine blocked Oxo-tremor, an effect that was reversed by propranolol. Atropine pretreatment also antagonized the potentiating effect of propranolol on Oxo-tremor. Propranolol inhibited mice brain cholinesterase at doses which enhanced Oxo-tremor. Timolol and sotalol produced a dose-dependent antagonism of Oxo-tremor, whereas practolol failed to produce a similar effect. None of these three agents produced any significant enhancement of Oxo-tremor. These results suggest the involvement of a peripheral mechanism for the antagonism and a central cholinergic mechanism for the facilitation of Oxo-tremor by propranolol.