Baclofen-impairment of memory retention in rats: possible interaction with adrenoceptor mechanism(s)
This study concerned the influence of adrenoceptor agonists and antagonists on baclofen-induced impairment of memory retention. Intracerebroventricular injection of baclofen (0.25-2 mug/rat) reduced memory retention in rats. The combination of different doses of baclofen with a low dose of clonidine (0.5 mug/rat) elicited a greater decrease in memory retention. Yohimbine (1 mug/rat) potentiated the response to a low dose, but decreased the response to higher doses of baclofen. Single administration of clonidine (0.5-2 mug/rat) but not yohimbine (1-4 mug/rat) itself decreased memory retention. The combination of clonidine with yohimbine did not show any interaction. The low dose of phenylephrine (0.5 mug/rat) or prazosin (0.5 mug/rat) also potentiated the inhibition of memory retention by baclofen. Phenylephrine (0.5-3 mug/rat) increased, while prazosin (0.5-2 mug/rat) decreased memory retention. The combination of the two drugs showed an interaction. It may be concluded that an adrenoceptor mechanism may interact with the memory retention impairment induced by baclofen. (C) 2001 Elsevier Science B.V. All rights reserved.