Regulation of Nicotinic Acetylcholine Receptor by Tyrosine Kinase in Autonomic Major Pelvic Ganglion Neurons

It is widely known that protein tyrosine kinases (PTKs) are involved in controlling many biological processes such as cell growth, differentiation, proliferation, survival and apoptosis. An $\alpha3\beta4$ subunit combination acts as a major functional acetylcholine receptor (nAChRs) in male rat major pelvic ganglion (MPG) neurons, and their activation induces fast inward currents and intracellular calcium increases. Recently it has been reported that the activity of acetylcholine receptors (AChRs) in some neurons can be negatively regulated by PTKs. However, the exact mechanism of regulation of nAChRs by PTKs is poorly understood. Therefore, we examined the potential role particular in nAChR by PTK using electrophysiology and calcium imaging in male rat MPG neurons. ACh induced inward currents and $(Ca^{2+})_i$ increases in MPG neurons, concomitantly. These responses were inhibited by more than 90% in $Na^+$- or $Ca^{2+}$- free solution. $\alpha$-conotoxin AuIB, a selective $\alpha3\beta4$ nAChR blocket, inhibited ACh-induced inward currents. Genistein (10 $\mu$M), a broad-spectrum tyrosine kinase inhibitor, markedly decreased ACh-induced currents and $Ca^{2+}$ transients, whereas 10 $\mu$M genistin, an inactive analogue, had little effect. Overall these data suggest that the activities of $\alpha3\beta4$ AChRs in MPG neurons are positively regulated by PTK. In conclusion, trosine kinase may be one of the key factors in the regulation of $\alpha3\beta4$ nAChRs in rat MPG neurons, which may play an important roles in the autonomic neuronal function such as synaptic transmission, autonomic reflex, and neuronal plasticity.