An α3β4 subunit combination acts as a major functional nicotinic acetylcholine receptor in male rat pelvic ganglion neurons

Abstract

We identified major subunits of the nicotinic acetylcholine receptor (nAChR) involved in excitatory postsynaptic potential and intracellular Ca(2+) ([Ca(2+)]i) increase in the major pelvic ganglion (MPG) neurons of the male rat. ACh elicited fast inward currents in both sympathetic and parasympathetic MPG neurons. Mecamylamine, a selective antagonist for alpha3beta4 nAChR, potently inhibited the ACh-induced currents in sympathetic and parasympathetic neurons (IC(50); 0.53 and 0.22 microM, respectively). Furthermore, alpha-conotoxin AuIB (10 microM), a new selective antagonist for alpha3beta4 nAChR, blocked more than 80% of the ACh-induced currents in MPG neurons. Conversely, alpha-bungarotoxin, alpha-methyllycaconitine, and dihydro-beta-erythroidine, known as blockers of the alpha7 or alpha4beta2, did not show selective blocking effects on MPG neurons. ACh transiently increased [Ca(2+)]i which was subsequently abolished in the extracellular Ca(2+)-free environment. Simultaneous recording of [Ca(2+)]i and ionic currents revealed that ACh increased [Ca(2+)]i under the conditions of the voltage-clamped (at -80 mV) state, and this resulted from the influx through nAChR itself. ACh-induced [Ca(2+)]i increase was blocked by mecamylamine (10 microM), but was not affected by atropine (1 microM). RT-PCR analysis showed that, among subunits of nAChR, alpha3 and beta4 were predominantly expressed in MPG. We suggest that activation of alpha3 and beta4 nAChR subunits in MPG neurons induce fast inward currents and [Ca(2+)]i increase, possibly mediating a major role in pelvic autonomic synaptic transmission.

Nicotine activates TRPM5-dependent and independent taste pathways

“…CT nerve tissue was collected in its exit from the tympanic bulla. RT-PCR was performed to screen for the presence of ␣-3, ␣-4, ␤-2, ␤-4 nAChR subunits (37), and ␣-gustducin and ␤-actin.…”

Alanine Scan of α-Conotoxin RegIIA Reveals a Selective α3β4 Nicotinic Acetylcholine Receptor Antagonist

“…In addition, genome-wide studies identified associations between lung cancer and several single nucleotide polymorphisms within the gene cluster encoding the ␣3, ␣5, and ␤4 nAChR subunits (10). Additionally, activation of the ␣3␤4 nAChR, a predominant subtype expressed in sympathetic and parasympathetic neurons of mammalian autonomic ganglia (11)(12)(13), is known to be associated with nicotine addiction and drug abuse (14,15). However, our understanding of the physiological relationship is limited.…”

Cross‐reactivity of acid‐sensing ion channel and Na+–H+ exchanger antagonists with nicotinic acetylcholine receptors

“…The habenula is involved in functions related to pain, stress, anxiety, sleep, and nicotine addiction and withdrawal, and its dysfunction has been linked to depression and schizophrenia (Hikosaka, 2010). The α3β4 * nAChRs are also highly expressed in autonomic ganglia (Park et al 2006). Consistent with the high expression of nAChRs in the CNS and peripheral nervous system, drugs interfering with these receptors have substantial potential to alter nAChR-mediated cellular and neuronal signalling, especially upon long-term treatment.…”