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 [Ca(2+)](i) transient triggered by depolarization in acutely dissociated neurones of the rat dorsal raphe and periventricular hypothalamic nuclei that express NPFF(2) and NPFF(1) receptors, respectively, in the absence and presence of 10 nM of NPA-NPFF or NPVF, two peptides selective for NPFF(2) and NPFF(1) receptors, respectively. In dorsal raphe neurones, NPA-NPFF reduces the inhibition of Ca(2+) conductances by nociceptin while NPVF is inactive. In periventricular hypothalamic neurones, both peptides reduce the inhibition of Ca(2+) transients by nociceptin, NPVF having a significantly larger effect than NPA-NPFF.