KHAN, H.; ALKINDI, A.Y.A.; SALEUDDIN, A.S.M.; Canad. Mem. Chiropractic Coll., Toronto, Canada; Sultan Qaboos Univ., Al-Khod, Oman; York Univ., Toronto, Canada: Neurosecretory (NS) cells of the reproductive centers in the central nervous system (CNS) of Helisoma (Mollusca: Pulmonata): Immunocytochemical and physiological studies using Aplysia (Mollusca: Opisthobranchia) egg-laying hormone (ELH).

The CNS of Helisoma consists of 11 ganglia encircling the esophagus. The superior part of the CNS is the paired cerebral ganglia and the cerebral commissure. Previously, we have shown that the caudodorsal NS cells (CDCs) of the cerebral ganglia are involved in the regulation of egg-laying (Khan et al. 1990. Can. J. Zool. 68:1233). A fluorescent dye, Lucifer Yellow (LY) was microinjected into the CDCs to explore their axonal pathways. Most LY injected CDC axons were seen to terminate in the cerebral commissure; however, many axons were also seen in other ganglia of the CNS, and in the visceral nerve. The LY microinjection studies in the CDCs revealed their complex axonal distribution. Antibodies against Aplysia ELH were immunocytochemically used to stain the CNS and reproductive system of Helisoma. Immunoreactive material (IR) was seen in the CDCs, various parts of the CNS and the reproductive system. The common hermaphroditic duct that transports eggs and sperms, which is the thinnest part of the reproductive system, displayed intense IR material. Various parts of the reproductive system were treated with synthetic ELH at physiological concentrations in vitro culture medium. These treatments produced visible contraction of the tracts. It has been suggested that the CDCs of Helisoma are homologous to the egg-laying centers of other mollusks, such as Aplysia, and that ELH-like peptide produces muscle contractions of the reproductive tract of Helisoma (Supported by grants from: NSERC, Canada and York University).