ANALGESIC ACTION OF PROPRANOLOL

Analgesic effects of propranolol were demonstrated in rats using the tail flick, and in mice using hot plate and writhing analgesic assays. Propranolol was shown to increase pain threshold in both rats and mice in this study.Propranolol increased pain threshold when given icv in small doses (100 μg in rat and 5 μg in mice), whereas, s. c. injection of 10 mg did not significantly modify the pain threshold. These findings suggest that the CNS is the main site of analgesic action of the drug. The results also showed an antagonism to the inhibition of the writhing response by propranolol and clenbuterol, a β2 adrenergic receptor agonist, indicating that the analgesic action is probably due to its β2 adrenergic blocking action.