The effects of pulsing magnetic fields on pineal melatonin synthesis in a teleost fish (brook trout, Salvelinus fontinalis)

Based on findings in various mammalian species, where exposure to electroma gnetic fields decreased the nocturnal synthesis of the pineal secretory pro duct melatonin, we investigated the effects of magnetic field (MF) exposure in a teleost fish, the brook trout (Salvelinus fontinalis). Fields were ge nerated by Helmholtz coils (maximum flux density 40 mu T, frequency 1 Hz, 2 00 ms on, 800 ms off). Melatonin concentrations were estimated by a specifi c radioimmunoassay. MF exposure significantly increased night-time pineal ( P < 0.001) and serum (P < 0.01) melatonin levels, as compared with the cont rols. It is suggested that either the pineal glands are directly affected, i.e. by an increased Ca2+-influx into pineal photoreceptors, or that the re sponses are indirect since induced currents, caused by the rapid rise and d ecay of the generated MF, may have disturbed the sensory system for electri c fields. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.