The antibodies against synthetic (183-192) fragments of beta2- and beta4-subunits of rat neuronal nicotinic acetylcholine receptor were used to study a beta-subunit composition of nicotinic receptors in the inferior mesenteric ganglion of the guinea pig by both immunocytochemical staining and blocking of excitatory postsynaptic potentials induced by electric stimulation of the pre-ganglionic nerve (intermesenteric trunk). The beta4-specific antibody stained 59.8 +/- 7.5% of neurons and inhibited the synaptic responses in all (n = 10) neurons studied by 25.5 +/- 1.8%. The beta2-specific antibody did not stain ganglionic neurons and did not affect the synaptic transmission. Taking into account the previously obtained data on the alpha-subunits found in this ganglion, it is concluded that the neurons of inferior mesenteric ganglion contain nicotinic receptors of alpha3(alpha5)beta4 subtypes involved in synaptic transmission through the intermesenteric tract.