[The disparate modulation by mu- and kappa-agonists of the cholinoceptor plasticity of the RPa3 and LPa3 neurons in the snail].

The existence of modulatory opiate mu- and kappa-receptors on the somata of identified RPa3 and LPa3 Helix neurons was shown using double microelectrode voltage clamp techniques. Agonists of these receptors, morphine and bremazocine, inhibit activity of somatic electrogenic cholinoreceptors. The equal quantities of mu-receptors but not kappa-receptors were found on the somata of RPa3 and LPa3 neurons. There were more kappa-receptors on the soma of RPa3 neuron that on the soma of LPa3. Both opioids (50-100 microM) had a reversible influence on an extinction depth of the inward current evoked by a local acetylcholine application into the soma (ACh-current) directions of both opioids' effects being mutually opposite. Morphine deepened the extinction of Ach-current of RPa3 neuron. Bremazocine loosened the extinction of Ach-current of RPa3 neuron and did not influence cholinoreceptor plasticity of LPa3 neuron.