Neuropeptide FF receptors couple to a cholera toxin-sensitive G-protein inrat dorsal raphe neurones

In rat dorsal raphe neurones, nociceptin (300 nM) reduced the peak [Ca2+](i ) transient, triggered by depolarization, by 36.7 +/- 1.8% (n = 46). This e ffect of nociceptin decreased to 16.7 +/- 2.9% (n = 18) after pre-treatment of the neurones with pertussis toxin (5 mug/ml, 2-6 h) but was unchanged ( 37.4 +/- 2.1%, n = 44) after pre-incubation with cholera toxin (5 mug/ml, 2 -6 h). This suggests that, in dorsal raphe neurones, the ORL1 receptor coup les to inhibitory (G(i/o)) G-proteins. The neuropeptide FF analogue, [D-Tyr (1), (N-Me)Phe(3)]neuropeptide FF (10, 100, 1000 nM), acted as an anti-opio id and reduced the effect of nociceptin (300 nM, 30 s) by 62.0 +/- 3.3% (n = 28). Following pre-incubation with cholera toxin (5 mug/ml, 2-6 h) [D-Tyr (1), (N-Me)Phe(3)] neuropeptide FF was unable, at the three concentrations tested, to block nociceptin activity. We conclude that, in rat dorsal raphe neurones, neuropeptide FF receptors couple to stimulatory G-proteins (G(s) ). (C) 2001 Elsevier Science B.V. All rights reserved.