Lectrical and Optical Study of Nerve Impulse-evoked Tp-induced, P2x-receptor-mediated Sympathetic Eurotransmission at Single Smooth Muscle Cells in Ouse Isolated Vas Deferens

bstract—Simultaneous electrophysiology and confocal miroscopy were used to investigate purinergic neurotransmision at single smooth muscle cells (SMCs) in mouse isolated as deferens, and to explore the relationship between two igh-resolution P2X-receptor-mediated measures of per ulse ATP release: transient peaks in the first time derivative f the rising phase of excitatory junction potentials (EJPs) ecorded in single SMCs (‘discrete events’; DEs) and neuroefector Ca transients (NCTs) in the impaled SMCs. This study shows that discrete events represent neuroransmitter release onto the impaled cell. First, the median mplitude of the first derivative of the EJP was larger when here was a coincident NCT in the impaled cell, compared ith instances when no coincident NCT occurred. Second, he time-to-peak amplitude of the first derivative was shorter f there was a coincident NCT in the impaled cell, compared ith when no coincident NCT was observed within the field. Surprisingly, first derivative amplitude increased with the istance (of the corresponding NCT) from the microelecrode. The microelectrode did not locally inhibit the funcional quantal size as there was no effect of distance on the ormalized NCT amplitude. When the significant effect of istance (between the microelectrode and NCTs) on the first erivative amplitude was removed, there was no correlation etween the unstandardized residual (of distance vs. first erivative amplitude) and NCT amplitude. The absence of a correlation between DE and NCT ampliudes suggests that the NCT amplitude is a poor measure of uantal size. The usefulness of NCTs hence lies primarily in ocating neurotransmitter release and measuring changes in ocal release probability. © 2007 IBRO. Published by Elsevier td. All rights reserved.