Secretory activity and serotonin innervation of subcommissural organ

We investigated immunohistochemically the subcommissural organ (SCO) glycoprotein secretion, its serotoninergic (5-HT) innervation and the possible control of this innervation upon the SCO activity in lizards (Agama impalearis, Saurodactylus mauritanicus and Eumeces algeriensis). Inside the SCO, interspecific differences in the intensity and the distribution of both secretary product and 5-HT nerve fibers were observed. Compared with Agama and Eumeces, the SCO of Saurodactylus displayed intense secretory products and several 5-HT fibers. In Saurodactylus, i.p. injection of parachlorophenylalanine, a potent inhibitor of 5-HT synthesis, produced a marked decrease of SCO secretory product. We report in this study species differences of the lizard SCO secretory activity and its possible physiological control by 5-HT innervation, as previously demonstrated in mammals.