@article {Rhim7608, author = {H Rhim and RJ Miller}, title = {Opioid receptors modulate diverse types of calcium channels in the nucleus tractus solitarius of the rat}, volume = {14}, number = {12}, pages = {7608--7615}, year = {1994}, doi = {10.1523/JNEUROSCI.14-12-07608.1994}, publisher = {Society for Neuroscience}, abstract = {We have investigated the coupling between opioid receptors and different types of Ca2+ channels in neurons acutely isolated from the nucleus tractus solitarius (NTS) of the rat. Using fura-2-based imaging we found that Ca2+ transients evoked by depolarization with 50 mM KCl were suppressed by the mu-opioid receptor agonist D-Ala2,N-MePhe4,Gly5- ol-enkephalin (DAMGO) and less effectively by the kappa-receptor agonist U-69,593. The delta-receptor agonist D-Pen2,D-Pen5-enkephalin (DPDPE) was ineffective. In whole-cell voltage-clamp recordings from these neurons, depolarizing voltage steps elicited high-threshold Ca2+ currents that could be distinguished pharmacologically into different components. Part of the current could be blocked by dihydropyridines, part by omega-conotoxin-GVIA and part by omega-agatoxin-IVA. This suggests that the neurons contained L-, N-, and P/Q-type Ca2+ channels. DAMGO and U-69,593 both blocked part of the Ca2+ current but DPDPE was ineffective. Perfusion of GTP-gamma-S into the cells produced a rapid rundown of the Ca2+ current and occluded further effects of the opioid agonists, suggesting the involvement of a G-protein in the coupling mechanism. Inhibition of L-channels did not alter the effect of DAMGO. On the other hand inhibition of N-channels occluded about 80\% of the effect of DAMGO. Inhibition of the P/Q-current occluded the remainder of the DAMGO effect. Thus, it appears that activation of opioid receptors can inhibit N- and P/Q-type Ca2+ channels but not L-channels in these cells. It is likely that such effects are important in opioid- mediated inhibition of transmitter release in the brain.}, issn = {0270-6474}, URL = {https://www.jneurosci.org/content/14/12/7608}, eprint = {https://www.jneurosci.org/content/14/12/7608.full.pdf}, journal = {Journal of Neuroscience} }