Study of the effects of nootropic agents on the adrenergic neurotransmission in smooth muscles of young and old animals.

The effects of compounds from the group of nootropic agents on the peripheral adrenergic neurotransmission in animals of different ages were studied in in vitro experiments. The experiments were performed on smooth muscle preparations isolated from young sexually mature (4-5-month-old) and old (22 month-old) rats treated twice daily for 7 days with 50 mg/kg of the nootropic agents piracetam, its structural analogues p-H and p-Cl, aniracetam and Ginseng extract. The animals were decapitated on the 7th day, the changes in the contractile responses of the smooth muscles to noradrenaline (NA) or electrical stimulation (ES) were studied in isolated preparations from vas deferens, aorta and anococcygeal muscle. The results show that the compounds studied can modulate the contractile effects of NA and ES, their action being most often potentiating and more pronounced in the smooth muscles manifesting weaker responses. In some cases the reactivity of the smooth muscle preparations to the stimuli applied was reduced after the nootropic agents. These effects can be partly explained with changes in the sensitivity of the pre- and postsynaptic alpha-adrenergic receptors. The possible variabilities in the influence on the two receptor populations in the different smooth muscles could explain the differences in the observed modulatory effects of the nootropic agents. The data obtained show that in prolonged therapeutic application of nootropic agents it is necessary to bear also in mind their possible influence on the peripheral neurotransmitter systems.