Physiological evidence (hypothermia) for central effects of beta-blocker agents.

In recent studies carried out during the last decade, it has been found that beta-blocker agents have many central effects. These findings raise the question how beta-blocker agents act when they influence central effects. In spite of intensive research efforts on this subject, no answer has been offered so far. Several studies indicate that the effect of beta-blocker agents on the dopaminergic receptors in the brain is very similar to their effect on beta-adrenergic receptors. In a set of experiments we checked the effect of two beta-blocker agents: oxprenolol and dl-propranolol, and the effect of d-propranolol on hypothermia induced by d-amphetamine and apomorphine at an ambient temperature of 4 degrees C. It was found that the two beta-blockers and the d-propranolol significantly potentiated the effect of hypothermia induced by d-amphetamine and apomorphine, an effect which is mediated by the central dopaminergic system. However, the activity of the beta-blockers was agonistic. Furthermore, the influence of d-propranolol on hypothermia shows that this dopaminergic agonistic activity of the beta-blockers is not related to peripheral or central beta-receptor blockage.