Korean J Physiol Pharmacol.  2002 Apr;6(2):63-70.

Muscarine M2 Receptor-mediated Presynaptic Inhibition of GABAergic Transmission in Rat Meynert Neurons

• Jang IS
• Akaike N

Abstract

Cholinergic modulation of GABAergic spontaneous miniature inhibitory postsynaptic currents (mIPSCs) by the activation of muscarine receptors was investigated in mechanically dissociated rat nucleus basalis of the Meynert neurons using the conventional whole-cell patch recording configuration. Muscarine (10microM) reversibly and concentration-dependently decreased mIPSC frequency without affecting the current amplitude distribution. Muscarine action on GABAergic mIPSCs was completely blocked by 1microM methoctramine, a selective M2 receptor antagonist, but not by 1microM pirenzepine, a selective M1 receptor antagonist. NEM (10microM), a G-protein uncoupler, attenuated the inhibitory action of muscarine on GABAergic mIPSC frequency. Muscarine still could decrease GABAergic mIPSC frequency even in the Ca2+-free external solution. However, the inhibitory action of muscarine on GABAergic mIPSCs was completely occluded in the presence of forskolin. The results suggest that muscarine acts presynaptically and reduces the probability of spontaneous GABA release, and that such muscarine-induced inhibitory action seems to be mediated by G-protein-coupled M2 receptors, via the reduction of cAMP production. Accordingly, M2 receptor-mediated disinhibition of nBM neurons might play one of important roles in the regulation of cholinergic outputs from nBM neurons as well as the excitability of nBM neurons themselves.

Keyword

Meynert; Cholinergic neurons; M2 receptor; GABAergic presynaptic nerve terminal; GABAergic mIPSCs; Mechanical dissociation; Presynaptic inhibition

MeSH Terms

Animals
Cholinergic Neurons
Colforsin
gamma-Aminobutyric Acid
GTP-Binding Proteins
Inhibitory Postsynaptic Potentials
Muscarine*
Neurons*
Pirenzepine
Rats*
Colforsin
GTP-Binding Proteins
Muscarine
Pirenzepine
gamma-Aminobutyric Acid