The present work examined, using in vivo microdialysis, the effects of 0.16-10 mg/kg of the β-adrenoceptor antagonists, (-)-pindolol and (±)-tertatolol, which have additional 5-HT1A receptor antagonist properties, on extracellular 5-HT levels in the ventral hippocampus of chloral hydrate-anaesthetized rats. These effects were compared with those observed when (-)-pindolol and (±)-tertatolol were given together with the 5-HT1A agonist 8-OH-DPAT (0.31 mg/kg i.p.). When given alone, (-)-pindolol and (±)-tertatolol increased 5-HT levels not only after systemic administration (at 2.5 and 10 mg/kg s.c.), but also when perfused locally through the dialysis probe (at a concentration of 10 μM). At doses equal to or lower than those that increased 5-HT when given alone, (-)-pindolol and (±)-tertatolol inhibited the decrease of extracellular 5-HT levels induced by 8-OH-DPAT. At higher doses, however, (-)-pindolol and (±)-tertatolol were less able to reverse these effects of 8-OH-DPAT. The selective β1-adrenoceptor antagonist, (±)-betaxolol, did not alter 5-HT levels, either when given alone or when given together with 8-OH-DPAT. Although the antagonism of the 8-OH-DPAT-induced decrease of 5-HT levels by (-)-pindolol and (±)-tertatolol is likely to be related to their 5-HT1A antagonist properties, their ability to increase extracellular 5-HT levels when given alone may involve interactions with 5-HT1B receptors at hippocampal 5-HT terminals.
- 5-HT receptor
- 5-HT receptor
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience