THE TREMOROLYTIC ACTION OF BETA-ADRENOCEPTOR BLOCKERS IN ESSENTIAL, PHYSIOLOGICAL AND ISOPRENALINE-INDUCED TREMOR IS MEDIATED BY BETA-ADRENOCEPTORS LOCATED IN A DEEP PERIPHERAL COMPARTMENT

1. The effects of intravenous propranolol 100 .mu.g kg-1, sotalol 500 .mu.g kg-1, timolol 7.8 .mu.g kg-1, atenolol 125 .mu.g kg-1 and placebo on essential, physiological and isoprenaline-induced tremor were studied. 2. These .beta.-adrenoceptor blocker doses produced equal reduction of standing-induced tachycardia in essential tremor patients. 3. Atenolol produced significantly less reduction of essential and isoprenaline-induced tremor than the non-selective drugs, confirming the importance of .beta.2-adrenoceptor blockade in these effects. 4. Propranolol and sotalol produced equal maximal inhibition of isoprenaline-induced tremor but propranolol was significantly more effective in reducing essential tremor. 5. The rate of development of the tremorolytic effect was similar in essential, physiological and isoprenaline-induced tremors but all tremor responses developed significantly more slowly than the heart rate responses. 6. It is proposed that these results indicate that the tremorolytic activity of .beta.-adrenoceptor blockers in essential, physiological and isoprenaline-induced tremor is exerted via the same .beta.2-adrenoceptors located in a deep peripheral compartment which is thought to be in the muscle spindles.