Abstract
The profile of opioid- and cannabinoid receptors in neurons of the nucleus tractus solitarius (NTS) have been studied using the whole cell configuration of the patch clamp technique. Experiments with selective agonists and antagonists of opioid, opioid-receptor-like-1 (ORL-1) receptor and cannabinoid receptors indicated that μ-opioid, κ-opioid, ORL-1 and CB1, but not δ-opioid, receptors inhibit VDCCs currents in NTS. Application of DAMGO (μ-opioid receptor agonist), Orphanin FQ (ORL-1 receptor agonist) and WIN55,122 (CB1 receptor agonist) caused inhibition of VDCCs currents in a concentration-dependent manner with an IC50 of 390 nM, 220 nM and 2.2 μM, respectively. Intracellular dialysis of the Gαi-protein antibody attenuated DAMGO-, Orphanin FQ- and WIN55,122-induced inhibition of IBa. Both pretreatment with adenylate cyclase inhibitor and intracellular dialysis of the protein kinase A (PKA) inhibitor attenuated WIN55,122-induced inhibition of IBa, but not DAMGO- and Orphanin FQ-induced inhibition. Mainly N- and P/Q-type VDCCs were inhibited by both DAMGO and Orphanin FQ, while L-type VDCCs were inhibited by WIN55,122. These results suggest that μ- and κ-opioid receptors and ORL-1 receptor inhibit N- and P/Q-type VDCCs via Gαi-proteins β γsubunits, whereas CB1 receptors inhibit L-type VDCCs via Gαi-proteins involving PKA in NTS. [J Physiol Sci. 2006;56 Suppl:S155]
