RESUMO
The alpha subunit composition of nicotinic acetylcholine receptors (nAChRs) expressed in the neurons of intracardiac ganglia of the rat was investigated using monoclonal and polyclonal antibodies against alpha3, alpha4, alpha5 and alpha7 nAChR subunits. The acetylcholine-induced membrane potentials in the neurons of the subepicardial plexus isolated from the left atrium of the heart were studied by intracellular recording performed in the presence of subunit-specific nAChR-blocking antibodies applied either separately or in various combinations. It was found that intracardiac ganglia neurons express alpha3alpha5; alpha7; alpha7(alpha5) and alpha4-containing nAChRs. The neurons were heterogeneous as to the nAChR subtypes expressed that possibly indicated their functional differences.
Assuntos
Gânglios Autônomos/metabolismo , Átrios do Coração/inervação , Neurônios/metabolismo , Receptores Nicotínicos/fisiologia , Acetilcolina/farmacologia , Animais , Células Cultivadas , Feminino , Gânglios Autônomos/citologia , Imuno-Histoquímica , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Neurônios/fisiologia , Subunidades Proteicas , Ratos , Receptores Nicotínicos/metabolismoRESUMO
All cultured neurons of rat superior cervical ganglion (SCG) were stained with nicotinic acetylcholine receptor (nAChR) alpha5- or alpha7-subunit-specific oligoclonal antibodies (Abs) and could additionally bind alpha3-subunit-specific monoclonal antibody (mAb). About 60% of the neurons were stained with alpha4-specific Ab and could not bind alpha3-specific mAb. The acetylcholine-induced membrane currents recorded with the whole-cell patch clamp method and partially blocked with alpha3-specific mAbs, could be additionally blocked with alpha5- and alpha7- specific Abs, and vice versa. The results suggest that: (1) each neuron of rat SCG expresses several nAChR subtypes with different alpha-subunits; (2) the alpha3-, alpha5- and alpha7-subunit-containing nAChRs are probably located far enough from each other thus enabling joint binding to the cell of the corresponding alpha-subunit specific Abs, in contrast to the alpha4-subunit-containing nAChRs which are probably located too close to the alpha3-containing ones to allow their joint binding.
