KHAN, H.R.*; MATSUSHIMA, O.; ALKINDI, A.Y.A.; SALEUDDIN, A.S.M.: Effects of serotonin, FMRFamide-related and vasopressin-related neuropeptides on free amino acid mediated osmoregulation in a pulmonate snail.

Osmoregulatory roles of serotonin and FMRFamide-related (FaRPs) in invertebrates have been shown in previous studies. We have studied the effects of serotonin, five FaRPs and three vasopressin-related neuropeptides on free amino acid (FAA) mediated intracellular osmoregulation by the kidney of the pulmonate snail, Helisoma. The levels of various intracellular FAAs in isolated kidney tissue pieces were measured after 30 min in vitro treatment with serotonin or one of the above neuropeptides in physiological saline. For control, the tissues were treated in physiological saline alone. Compared to controls, the levels of FAAs increased significantly in various treatments. The treatments with neuropeptides were more effective than serotonin. The presence of immunoreative (IR) substance to arginine vasopressin and conopressin (vasopressin-related molluscan neuropeptide) were studied in the central nervous system (CNS) and kidney by immunocytochemistry. The IR neurons are present in all ganglia of the CNS except the buccal and pleural ganglia. Large IR neurons were found in the visceral and left parietal ganglia which innervate the kidney, and many IR fibers and varicosities in the kidney tissue were also seen. Osmoregulation by serotonin and the neuropeptides in the snail will be discussed.