(-)-Penbutolol as a blocker of central 5-HT1A receptor-mediated responses

Brain 5-HT1A and 5-HT1B receptors are important targets for drug-induced modulation of 5-HT function in vivo. However, very few compounds are available that are effective antagonists at 5-HT1 receptors, thus hampering the progress of fundamental as well as clinical research in this area. The present study assessed the usefulness of the beta-adrenolytic agent (-)-penbutolol (and its (+)-counterpart) as a 5-HT1A receptor-blocking agent. The compound was found to counteract, in a stereospecific fashion, not only the behavioural and hypothermic but also the in vivo 5-HT synthesis/turnover-reducing effects of the specific 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). These findings indicate that (-)-penbutolol is an antagonist at both postsynaptic receptors and somatodendritic autoreceptors of the 5-HT1A subtype. Thus, (-)-penbutolol represents a useful addition to the array of pharmacological tools available for the study of central 5-HT1 receptor-mediated functions.