β2 Adrenoreceptor-Mediated Noradrenergic Effect on GABA-ergic Transmission in the CA1 Zone of the Rat Hippocampus in vitro

Abstract

Using extracellular recording of evoked potentials, we examined the effect of an agonist of β 2 adrenoreceptors, metaproterenol (MPT), on GABA-ergic transmission in the CA1 zone of slices of the rat hippocampus. Isolated application of GABA evoked in these slices rapid reversible suppression of orthodromic population discharges recorded from the pyramidal layer of the above hippocampal zone after electrical stimulation of Schaffer collaterals in the radial layer. In most cases (13 of 19 preparations), combined application of GABA and MPT interfered with the development of the inhibitory GABA effect. In the case of the action of both of the above agents, the amplitude and duration of evoked responses decreased, but these changes were significantly weaker than those observed upon isolated GABA application. Our experiments showed that the noradrenergic system is capable of modulating GABA-ergic inhibition via β 2 adrenoreceptors and, in such a way, is probably involved in regulation of the inhibition level in the hippocampus. Noradrenaline-induced effects on inhibitory neuronal networks in the hippocampus, similarly to those exerted by several other cerebral neurotransmitter systems, underlie the involvement of the noradrenergic cerebral system in a few physiological processes (emotions, attention, and memory) and are related to some pathological states (Alzheimer’s disease, schizophrenia, epilepsy, etc.).