Pharmacological and molecular characterization of P2X receptors in rat pelvic ganglion neurons

Abstract

1 The presence and characteristics of P2X receptors on neurons of the rat major pelvic ganglia (MPG) have been studied using whole cell voltage-clamp, in situ hybridization and immunohistochemistry. 2 Rapid application of ATP (100 mM) to isolated rat MPG neurons induced moderately large inward currents (0.33 ± 5.3 nA) in 39% of cells (108/277). The response to ATP occurred very rapidly, with an increase in membrane conductance, and desensitized slowly. 3 The concentration-response curve for ATP yielded an EC 50 of 58.9 mM. The agonist pro®le was ATP52MeSATP=ATPgS4BzATP, while a,b-MeATP, b,g-MeATP, UTP and ADP were all inactive at concentrations up to 100 mM. 4 The response to ATP was antagonized by suramin (pA 2 =5.6), reactive blue-2 (IC 50 =0.7 mM) and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS). 5 Lowering the pH from 7.4 to 6.8 produced a marked potentiation (to 339% of control) of the responses to ATP (30 mM), while raising the pH to 8.0 attenuated the responses (to 20% of control). The EC 50 s for ATP were 28.8, 58.9 and 264 mM at pH 6.8, 7.4 and 8.0, respectively. 6 Co-application of ATP with Zn 2+ produced a marked enhancement of the responses to ATP, with an EC 50 of 9.55 mM. In the presence of Zn 2+ (30 mM), the EC 50 for ATP was decreased to 4.57 mM. 7 In situ hybridization revealed that the P2X receptor transcripts levels in rat MPG neurons are P2X 2 4P2X 4 4P2X 1 , P2X 3 , P2X 5 and P2X 6 . The immunohistochemical staining revealed a small number of neurons with strong P2X 2 immunoreactivity. 8 In conclusion, our results indicate that there are P2X receptors present on MPG neurons. The pharmacological characteristics of these receptors, the in situ hybridization and immunohistochemical evidence are consistent with them being of the P2X 2 subtype, or heteromultimers, with P2X 2 being the dominant component.

Neural Control of the Lower Urinary Tract

“…Although 2-MeSATP and ATP are approximately equipotent in rat neurons α,β-me-ATP evokes only small responses consistent with the immunohistochemical data indicating that high levels of P2X2 receptors but not P2X1 or P2X3 receptors are expressed in these ganglia (737). On the other hand at least three types of P2X receptors are expressed in guinea pig pelvic ganglia (P2X2, P2X3, and P2X2/3) (736).…”

“…Patch clamp recordings in dissociated neurons from the rat and rabbit pelvic ganglia (475), and guinea pig bladder ganglia (737) revealed that ATP evokes a rapid depolarization or inward current via P2X receptors. Although 2-MeSATP and ATP are approximately equipotent in rat neurons α,β-me-ATP evokes only small responses consistent with the immunohistochemical data indicating that high levels of P2X2 receptors but not P2X1 or P2X3 receptors are expressed in these ganglia (737).…”

Molecular Physiology of P2X Receptors

“…About 40% of rat pelvic ganglion cells show robust responses to ATP that have all the characteristics of the P2X 2 receptor, including potentiation by protons and zinc, ineffectiveness of ␣␤meATP, and block by suramin (IC 50 ϳ1 M) and PPADS; these cells also express abundant P2X 2 receptor immunoreactivity, and it is concluded that homomeric P2X 2 receptors probably underlie the response (518). In more recent studies, Zhong et al (517) have shown that guinea pig pelvic ganglion neurons differ substantially from those of the rat.…”

Purinergic signalling in the urinary tract in health and disease

“…P2X receptors have been demonstrated in pelvic ganglion neurones of rat [762] and guinea-pig [761]. In the rat, evidence from the pharmacological characteristics of pelvic ganglion neurones in response to P2 agonists and antagonists recorded with the whole cell voltage-clamp technique combined with in situ hybridisation and immunohistochemistry led to the conclusion that P2X2 receptors are the predominant P2X subtype present in about 39 % of the neurones.…”