Melatonin: neuritogenesis and neuroprotective effects in crustacean x-organ cells.
Melatonin has both neuritogenic and neuroprotective effects in mammalian cell lines such as neuroblastoma cells. The mechanisms of action include receptor-coupled processes, direct binding and modulation of calmodulin and protein kinase C, and direct scavenging of free radicals. While melatonin is produced in invertebrates and has influences on their physiology and behavior, little is known about its mechanisms of action. We studied the influence of melatonin on neuritogenesis in well-differentiated, extensively-arborized crustacean x-organ neurosecretory neurons. Melatonin significantly increased neurite area in the first 24h of culture. The more physiological concentrations, 1 nM and 1 pM, increased area at 48 h also, whereas the pharmacological 1 μM concentration appeared to have desensitizing effects by this time. Luzindole, a vertebrate melatonin receptor antagonist, had surprising and significant agonist-like effects in these invertebrate cells. Melatonin receptors have not yet been studied in invertebrates. However, the presence of membrane-bound receptors in this population of crustacean neurons is indicated by this study. Melatonin also has significant neuroprotective effects, reversing the inhibition of neuritogenesis by 200 and 500 μM hydrogen peroxide. Because this is at least in part a direct action not requiring a receptor, melatonin's protection from oxidative stress is not surprisingly phylogenetically-conserved.
Department of Biology, Colby College, 5720 Mayflower Hill, Waterville, ME 04901, USA.
Gregory A
GA
Cary
Anne S
AS
Cuttler
Kirsten A
KA
Duda
Escar T
ET
Kusema
Jennifer A
JA
Myers
Andrea R
AR
Tilden
D000818:Animals; D060829:Arthropod Proteins / Q000378:metabolism; D003386:Brachyura / Q000187:drug effects* / Q000378:metabolism; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008550:Melatonin / Q000378:metabolism / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000378:metabolism / Q000494:pharmacology*; D009490:Neurosecretory Systems / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D044094:Receptors, Melatonin / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014363:Tryptamines / Q000494:pharmacology
D060829:Arthropod Proteins; D018696:Neuroprotective Agents; D044094:Receptors, Melatonin; D014363:Tryptamines; C057154:luzindole; D006861:Hydrogen Peroxide; D008550:Melatonin