α-Subunit Composition of Nicotinic Cholinoreceptors of Neurons of the Inferior Mesenteric Ganglion of the Guinea Pig: an Electrophysiological Study

Abstract

We studied the subunit composition of nicotinic cholinoreceptors (nChR) of neurons of the inferior mesenteric ganglion (IMG) of the guinea pig using antibodies against the α3, α4, α5, and α7 nChR subunits and a standard technique of intracellular recording. Application of the α3 subunit-specific antibodies resulted in a decrease in the EPSP amplitude by 29.7 ± 1.8%, on average, in 17 of 20 studied neurons. The α4 subunit-specific antibodies evoked no changes in the amplitude of EPSP recorded from IMG neurons (n = 10). Effects of the α5 subunit-specific antibodies were studied in 20 neurons, where the EPSP amplitude dropped after application of these antibodies by 40.0 ± 1.8%, on average. Superfusion of the neurons with a solution containing the α3 and α5 subunit-specific antibodies completely suppressed synaptic responses (n = 3). The α7 subunit-specific antibodies provided an increase in the EPSP amplitude in 13 of 15 studied IMG neurons (by 37 ± 6%, on average); this fact allows us to suppose that α7-containing nChR are present in the IMG neurons and are indirectly involved in the processes of synaptic transmission. Application of the antibodies evoked no significant shifts in the membrane potential in IMG neurons. Our findings demonstrate that synaptic transmission through the guinea pig IMG is realized mostly with the involvement of the α3- and α5-containing nChR; the α4-containing receptors are not engaged in this process.