sentence: Alternatively , it may be that the adverse effects of pindolol and propranolol are due to the simultaneous blockade of both beta 1- and beta 2-adrenoceptors .
paragraph: 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 directly into the brain ventricular system (ICV). Additionally, atenolol and metoprolol were evaluated to see whether differential delivery to the brain contributed to the observed lack of effect of systemically administered beta 1-adrenoceptor antagonists. ICV administration of pindolol (45 or 90 micrograms) was followed by a suppression of copulation. At 45 micrograms, inhibition was limited to performance aspects of copulation, whereas at 90 micrograms, decrements in motivational and performance aspects of copulation were evident. ICV administration of propranolol also suppressed copulatory behavior. At 45 micrograms, no significant effects were observed, whereas at 90 micrograms decrements in motivational and performance 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 involve interactions with 5-HT1A receptors in the CNS. Alternatively , it may be that the adverse effects of pindolol and propranolol are due to the simultaneous blockade of both beta 1- and beta 2-adrenoceptors .