NERVE GROWTH-FACTOR MAINTAINS REGULATION OF INTRACELLULAR CALCIUM IN NEONATAL SYMPATHETIC NEURONS BUT NOT IN MATURE OR AGED NEURONS

We examined the effects of nerve growth factor on the regulation of in tracellular calcium levels of superior cervical ganglion neurons in te rms of postnatal maturation and ageing. Rat superior cervical ganglion neurons from three age groups (neonatal: 0 to one-day-old, young adul t: three to six-month-old, and aged: more than 24-month-old) were diss ociated and cultured in the presence or absence of 100 ng/ml of nerve growth factor. Intracellular free calcium levels ([Ca2+](i)) were meas ured using the fura-2 microfluorometry. Nerve growth factor treatment increased the resting [Ca2+](i) of neonatal neurons, although it had n o effect on those of mature and aged neurons. We further examined the effects of nerve growth factor on the transient increase of [Ca2+](i) induced by methacholine (0.1 mM), caffeine (20 mM) or high-potassium m edium (40 mM K+). Nerve growth factor pre-treatment significantly incr eased the population of neonatal superior cervical ganglion neurons wh ich responded to methacholine, whereas almost all young adult and aged neurons responded to methacholine regardless of pre-treatment of nerv e growth factor. Caffeine induced a cyclic alteration of [Ca2+](i) (os cillation) in 45% of the neonatal superior cervical ganglion neurons w hen they were maintained without nerve growth factor, but nerve growth factor treatment suppressed the oscillation to 10% of neurons. In con trast to neonatal neurons, all of the young adult and aged neurons sho wed only a transient increase of [Ca2+](i) in response to caffeine ind ependent of nerve growth factor treatment. There was no significant ef fect of nerve growth factor on K+ depolarization-induced [Ca2+](i) ele vations at any of the ages studied. Nerve growth factor did not substa ntially alter the pattern of the transients induced by these three age nts. Our results indicate that exogenous nerve growth factor is necess ary to maintain normal acetylcholine receptor-mediated [Ca2+](i) respo nses as well as Ca2+-induced Ca2+ release from intracellular calcium s torage in neonatal superior cervical ganglion neurons. In mature super ior cervical ganglion neurons, Ca2+ homeostasis becomes independent of exogenous nerve growth factor, and Ca2+ homeostasis and its independe ncy are well preserved in aged neurons. (C) 1997 IBRO. Published by El sevier Science Ltd.