[Regulation of the efficacy of adrenergic synaptic transmission by autoadrenoreceptors in rat brain slices].

A hypothesis of the role of autoadrenoreceptors in the processes of synaptic depression, facilitation, PSP amplitude stabilization and amplitude increase with the stimulation frequency growth is described by means of a mathematical model. Synaptic depression is realized by activation of alpha-autoadrenoreceptors, synaptic facilitation--by beta-autoadrenoreceptors activation. A "stable secretion zone" is formed between the autoadrenoreceptor activation curves at which noradrenaline secretion is stabilized. Experimental studies of H3-NA secretion from rats cerebral cortex slices showed that autoadrenoreceptors really form a stable secretion zone. The presence of stable secretion zone provides for self-facilitation and stabilization of H3-NA secretion elicited by 5-fold consecutive K+-depolarizations of slices with time interval 30 min. The absence of the stable secretion zone leads to destabilization of H3-NA secretion. With an increase of the stimulation intensity the curves of autoadrenoreceptors activity and stable secretion zone shift toward high noradrenaline concentrations.