Galanin receptor/Neuropeptide Y receptor interactions in the dorsal raphe nucleus of the rat

The aim of this study was to evaluate by quantitative receptor autoradiography the interactions between Neuropeptide Y Y1 (NPY Y1) and Galanin (GAL) receptors in the dorsal raphe nucleus (DRN) where both GAL receptors and NPY Y1 receptors exist. The ability of the GAL receptor antagonist M35 to block the GAL action was also evaluated. Double immunocytochemical staining of 5-hydroxytryptmine and c-Fos and stereology techniques were used to study the specific cell activation in the DRN after the intracerebroventricular coinjections of GAL and the NPY Y1/Y5 agonist [125I] Leu31,Pro34PYY.GAL (0.3 nM) decreases [125I] Leu31,Pro34PYY binding in the DRN by 48% (p < 0.01) as shown by quantitative receptor autoradiography. This effect was reversed with the GAL receptor antagonist M35. Intracerebroventricular coinjections of NPY Y1/Y5 agonist and GAL reduced the c-Fos expression in the serotoninergic cells induced by the NPY Y1/Y5 agonist in DRN. These results indicate the existence of antagonistic interactions between GAL receptors and NPY Y1 receptors in the DRN that may be of relevance in mood disorders.

► GAL decreases [125I] Leu31,Pro34PYY agonist binding in the DRN.
► The GAL antagonist M35 reverses the effect produced by GAL on NPY Y1/Y5 binding.
► The coinjection of NPY Y1/Y5 agonist and GAL reduced the c-Fos IR in DRN.
► The coinjection of NPY Y1/Y5 agonist and GAL reduced the c-Fos IR serotoninergic cell bodies in DRN.
► These results indicate the existence of an antagonistic interaction GALR/NPY Y1 receptors in the DRN.