Expression patterns and behavioral effects of conopressin and APGWamide in the nudibranch Berghia stephanieae.

The highly conserved oxytocin/vasopressin family of nonapeptides plays many roles across the animal kingdom, from osmoregulation to reproductive physiology. We investigated the expression patterns and pharmacological effects of the gastropod ortholog of this peptide, conopressin, along with another peptide involved in gastropod reproduction, APGWamide, in the nudibranch Berghia stephanieae. A brain transcriptome was used to identify and annotate the gene sequences for the peptides and one conopressin receptor. In-situ hybridization chain reaction showed that many neurons in the brain expressed these peptides. However, the peptide genes were co-expressed by only three neurons, which were in the right cerebral ganglion, the same side on which the reproductive organs are located. A conopressin receptor (BSCPR1) was expressed in a prominent population of APGWamide expressing neurons. Placing animals in a solution containing the APGWamide peptide caused minimal behavioral changes. However, exposure to conopressin reduced locomotion, increased gut contractions, and caused voiding at high concentration. The genes for these peptides and BSCPR1 were expressed in cells in the digestive system. BSCPR1 was also expressed by a line of neurons on the anterior portion of the radula and would be contacted during feeding. APGWamide-expressing neurons were found in the genital ganglion. All three genes expressed in cells on sensory appendages. These results are consistent with the conopressin playing a variety of roles in the brain and the body and being involved in both reproduction and digestion. This study sheds light on the function of this ancient nonapeptide in a new-to-neuroscience invertebrate species.