Beta-adrenoceptor agonists do not cause tremor in the conscious rat

The ability of some beta-adrenoceptor agonists to induce tremor via skeletal muscle beta 2-adrenoceptors in conscious unrestrained rats has been investigated. Tremor was assessed by visual observation and by an objective method based on accelerometry. Infusion of isoprenaline or terbutaline did not cause tremor, neither did beta-stimulation potentiate an established mild tremor produced by central muscarinic receptor stimulation. Since beta-agonists readily produce tremor in man via skeletal muscle beta 2-adrenoceptor stimulation, our findings indicate that these receptors have a different function in the rat.