Blockade of 5-hydroxytryptamine receptors in the central nervous system by β-adrenoceptor antagonists

(±)-propranolol, oxprenolol and pindolol in doses ranging from 0.5 to 5 mg/kg antagonised the head twitch produced in mice by 5HTP. These doses had no effect on the pinna reflex. (+) propranolol was inactive. These β-adrenoceptor antagonists also prevented the induction of sleep in 5-day old chicks by 5HT. Their activities in the two tests were similar to their 5HT receptor blocking potencies in the rat fundus preparation. It is suggested that these β-adrenoceptor antagonists may block some 5HT receptors in the central nervous system.