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Pelvic ganglia (PG) play critical roles in relaying sympathetic and parasympathetic information from the spinal cord to the penile vasculature and, controlling the penile reflex. Animal studies have shown that androgen deprivation by castration causes erectile dysfunction (ED). Until now, however, neural mechanisms underlying castration-induced ED remain unclear. Therefore, we examined whether androgen deprivation down-regulates nicotinic acetylcholine receptors (nAchRs), which mediate fast excitatory synaptic transmission in the PG. Toward this end, neurogenic ED was demonstrated by measuring the intracavernous pressure in castrated rats. Real-time PCR analysis revealed that the transcripts encoding nAchR α3/α5/β4 subunits were significantly down-regulated in the PG neurons. In addition, down-regulation of the nAchR subunits was reversed by replacement of testosterone. Patch-clamp experiments showed that the nAchR currents were selectively attenuated in the parasympathetic PG neurons innervating the penile vasculature, activation of which elicits penile erection. Taken together, our data suggest that phenotype-specific down-regulation of nAchRs in the PG neurons may contribute to the neurogenic ED in castrated rats., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

The electrophysiological mechanism underlying afterhyperpolarization induced by the activation of the nicotinic acetylcholine receptor (nAChR) in male rat major pelvic ganglion neurons (MPG) was investigated using a gramicidin-perforated patch clamp and microscopic fluorescence measurement system. Acetylcholine (ACh) induced fast depolarization through the activation of nAChR, followed by a sustained hyperpolarization after the removal of ACh in a dose-dependent manner (10 microM to 1mM). ACh increased both intracellular Ca(2+) ([Ca(2+)](i)) and Na(+) concentrations ([Na(+)](i)) in MPG neurons. The recovery of [Na(+)](i) after the removal of ACh was markedly delayed by ouabain (100 microM), an inhibitor of Na(+)/K(+) ATPase. Pretreatment with ouabain blocked ACh-induced hyperpolarization by 67.2+/-5.4% (n=7). ACh-induced hyperpolarization was partially attenuated by either the chelation of [Ca(2+)](i) with BAPTA/AM (20 microM) or the blockade of small-conductance Ca(2+)-activated K(+) channels by apamin (500 nM). Taken together, the activation of nAChR increases [Na(+)](i) and [Ca(2+)](i), which activates Na(+)/K(+) ATPase and Ca(2+)-activated K(+) channels, respectively. Consequently, hyperpolarization occurs after the activation of nAChR in the autonomic pelvic ganglia., ((c) 2010 Elsevier Ireland Ltd. All rights reserved.)

Several pharmacological and physiological studies have suggested that GABA(A) receptors (GABA(A) Rs) may exist in the rat major pelvic ganglion (MPG), a large coalescent pelvic ganglion that contains both sympathetic and parasympathetic components which innervates pelvic organs. However, the presence of GABA(A) R in the MPG has never been demonstrated directly by morphological studies. In the present study, we used immunohistochemistry to demonstrate the existence of GABA(A) R beta2/3 subunits for the first time in the rat MPG. We also analyzed the neurochemical properties of MPG neurons expressing GABA(A) R beta2/3 subunits. GABA(A) R beta2/3-immunoreactive (-IR) neurons occupied 27.4+/-7.0% of the whole neuronal population, and many of these (77.6%) were co-localized with tyrosine hydroxylase (TH). Likewise, most (86.5%) of TH-IR neurons were GABA(A) R beta2/3-positive. GABA(A) R beta2/3 subunits were also expressed in a few VIP- or NOS-IR neurons, the cholinergic or non-adrenergic, non-cholinergic (NANC) neurons. These results suggest that GABA(A) Rs are involved in the modulation of most sympathetic, noradrenergic neurons and also a subset of VIP and NOS neurons of the rat MPG.

Although nerve injury is known to up- and down-regulate some metabotropic receptors in vagal afferent neurons of the nodose ganglia (NG), the functional significance has not been elucidated. In the present study, thus, we examined whether nerve injury affected receptor-mediated Ca2+ channel modulation in the NG neurons. In this regard, unilateral vagotomy was performed using male Sprague-Dawley rats. One week after vagotomy, Ca2+ currents were recorded using the whole-cell variant of patch-clamp technique in enzymatically dissociated NG neurons. In sham controls, norepinephrine (NE)-induced Ca2+ current inhibition was negligible. Following vagotomy, however, the NE responses were dramatically increased. This phenomenon was in accordance with up-regulation of alpha2A/B-adrenergic receptor mRNAs as quantified using real-time RT-PCR analysis. In addition, neuropeptide Y (NPY) and prostaglandin E2 responses were moderately augmented in vagotomized NG neurons. The altered NPY response appears to be caused by up-regulation of Y2 receptors negatively coupled to Ca2+ channels. In contrast, nerve injury significantly suppressed opioid (tested with DAMGO)-induced Ca2+ current inhibition with down-regulation of micro-receptors. Taken together, these results demonstrated for the first time that the profile of neurotransmitter-induced Ca2+ channel modulation is significantly altered in the NG neurons under pathophysiological state of nerve injury.