Localization of molluscan R15α2 peptide immunoreactivity in the mammalian brain

Abstract

The R15 neuropeptides have been identified in the marine mollusc Aplysia californica. They compose a new family of neuropeptides acting on the cardiovascular, digestive, respiratory, reproductive and nervous system. In this report we show that one of the members of the R15 neuropeptide family, the α2 peptide is conserved in lower mammals. We have identified R15α2 immunoreactive neurons in the neurosecretory cell groups of the hypothalamus and in the brainstem of the hedgehog ( Erinaceus europaeus). The majority of labeled cells were localized to the anterior periventricular part of the paraventricular nucleus and the accessory neurosecretory cell groups in the lateral hypothalamus as well as to the dorsal part of the nucleus tractus solitarii. In the paraventricular nucleus, R15α2 immunoreactive neurons also exhibit immunoreactivity for oxytocin, cortocotropin releasing factor, vasoactive intestinal polypeptide and for the FMRFamide-related peptide which we found to be conserved in the hedgehog brain as well. No complete colocalization of R15α2 with any of the neuroactive substances tested, is observed. The highest degree of coexistence occurs with FMRFamide-related peptide, followed by vasoactive intestinal polypeptide, oxytocin and corticotropin releasing factor.