CENTRAL PROPRANOLOL AND PINDOLOL, BUT NOT ATENOLOL NOR METOPROLOL, INHIBIT SEXUAL-BEHAVIOR IN MALE-RATS

Are the anti-sexual effects of propranolol and pindolol due to actions within the brain? To answer this, these agents were administered dire ctly into the brain ventricular system (ICV). Additionally, atenolol a nd metoprolol were evaluated to see whether differential delivery to t he brain contributed to the observed lack of effect of systemically ad ministered beta(1)-adrenoceptor antagonists. ICV administration of pin dolol (45 or 90 mu g) was followed by a suppression of copulation. At 45 mu g, inhibition was limited to performance aspects of copulation, whereas at 90 mu g, decrements in motivational and performance aspects of copulation were evident. ICV administration of propranolol also su ppressed copulatory behavior. At 45 mu g, no significant effects were observed, whereas at 90 mu g decrements in motivational and performanc e aspects of copulation were evident. In contrast, ICV administration of the beta(1)-adrenoceptor antagonists, atenolol and metoprolol, was not associated with any major modifications in copulatory behavior. We suggest that the inhibitory effects of propranolol and pindolol may i nvolve interactions with 5-HT1A receptors in the CNS. Alternatively, i t may be that the adverse effects of pindolol and propranolol are due to the simultaneous blockade of both beta(1)- and beta(2)-adrenoceptor s.