Meeting Abstract

P1.82  Sunday, Jan. 4  Neuroprotective and neuritogenic effects of melatonin on crustacean x-organ cells CARY, Gregory; CUTTLER, Anne; KUSEMA, Escar; MYERS, Jennifer; DUDA, Kirsten; TILDEN, Andrea*; University of Washington; Colby College; Colby College; Colby College; Colby College; Colby College artilden@colby.edu

The vertebrate pineal hormone melatonin has protective effects in the mammalian nervous system. These effects are both receptor-mediated and non-receptor-mediated. Melatonin has not been extensively studied in invertebrates; however, invertebrates do produce melatonin, with daily variations that suggest a circadian pattern as in vertebrates. Crustaceans respond to exogenous melatonin with changes in activity patterns, glucose metabolism, and cardiac rate, all of which are influenced also by well-characterized neuropeptide products of the x-organ/sinus gland system in the eyestalk. We studied the influence of melatonin on neurite growth of x-organ cells from the fiddler crab Uca pugilator. In culture, these cells grow neurites with extensive arborizations within the first 48 hr. Melatonin, 1 M, 1nM, and 1 pM, significantly increased neurite growth versus control cells after 24 hr in culture. The physiological concentrations, 1 nM and 1 pM, increased growth at 48 hr also, whereas the pharmacological 1M dosage showed desensitizing effects by this time. Luzindole, a vertebrate melatonin receptor antagonist, had agonist-like activity in these crustacean cells, indicating a potentially different type of membrane receptor from vertebrates. Melatonin also had protective effects, reversing the neurite-inhibiting administration of hydrogen peroxide. This neuroprotective influence of melatonin is likely due to the ubiquitous ability of melatonin to scavenge free radicals directly. Results of this study indicate roles of melatonin in the crustacean nervous system that are analogous to its roles in the vertebrate nervous system.