LS-2-P-1507 Presence and Distribution of Ghrelin Receptor in the Nervous System of Pomacea canaliculata

Growth hormone secretagogue-receptor 1a (GHS-R1a), a member of the G-protein couple receptor family, is a natural receptor for gastrointestinal hormones, especially ghrelin peptide. The ghrelin-GHS-R1a complex has an ability to stimulate the releasing of growth hormone from the pituitary gland. In vertebrates, GHS-R1a has been identified in the central nervous system, mainly the hypothalamus. In the present study, the immunohistochemistry technique was used to examine the localization and distribution of GSH-R1a in the nervous system of the golden apple snail, Pomacea canaliculata. Pairs of the snail ganglia were investigated, including cerebral, buccal, and pleuropedal ganglia. Histologically, the snail neuronal cells had been classified into four types, according to their sizes into NR1-4 (small-, medium-, large-sized neurons and giant neuron, respectively). From the immunoperoxidase technique, the immunoreactivity of GHS-R1a was identified in the neurons housed in the pleuropedal ganglion. In contrast, no immunoreactive neurons were observed in the cerebral and buccal ganglia. The immunoreactivity showed a strongly staining only in the NR1 and NR3. The immunoreactive neurons was scattered throughout the pleuropedal ganglion. However, the highest number of the immunoreactive neurons was observed at the peripheral of the neuropil. This result was confirmed by the immunofluorescence technique. In summary, we have demonstrated that GHS-R1a was localized and distributed in the ganglion of this gastropod mollusk. We suggest that ghrelin peptide which is a ligand for this receptor could play a physiological function in this species.