Neuropeptide FF receptors 1 and 2 exert an anti-opioid activity in acutely dissociated rat dorsal raphe and periventricular hypothalamic neurones

We measured the reduction by nociceptin of the [Ca2+](i) transient triggered by depolarization in acutely dissociated neurones of the rat dorsal raphe and periventricular hypothalamic nuclei that express NPFF2 and NPFF1 receptors, respectively, in the absence and presence of 10 nM of NPA-NPFF or NPVF, two peptides selective for NPFF2 and NPFF1 receptors, respectively. In dorsal raphe neurones, NPA-NPFF reduces the inhibition of Ca2+ conductances by nociceptin while NPVF is inactive. In periventricular hypothalamic neurones, both peptides reduce the inhibition of Ca2+ transients by nociceptin, NPVF having a significantly larger effect than NPA-NPFF. These results demonstrate that activation of both NPFF1 and NPFF2 receptors has the same cellular anti-opioid effect. (C) 2003 Elsevier Ireland Ltd. All rights reserved.