Neuropeptide Y actions and the distribution of Ca2+-dependent Cl- conductance in rat dorsal root ganglion neurons.

Neuropeptide Y (NPY) increases the excitability of 'small', nociceptive, dorsal root ganglion (DRG) neurons. This effect, which may contribute to the etiology of 'neuropathic' pain, has been attributed to attenuation of Ca2+-sensitive K+ conductance(s) (gK,Ca) following suppression of Ca2+ entry via N-type Ca2+ channels. A problem arises with this conclusion because rat DRG neurons normally contain high intracellular Cl- and some of them express a Ca2+-dependent Cl- conductance (gCl,Ca). In this study, we find that in rat DRG neurons increasing intracellular Cl- does not attenuate the effect of 1 microM NPY because gCl,Ca is not found in 'small' DRG cells and the peptide failed to affect the gCl,Ca found in 'large' cells. Thus, the presence of gCl,Ca in a subpopulation of 'large' DRG neurons does not alter the conclusion that excitatory effects of NPY result from attenuation of gK,Ca.