NERVE GROWTH-FACTOR (NGF) ACUTELY ENHANCES HIGH-VOLTAGE ACTIVATED CALCIUM CURRENTS IN MOLLUSCAN NEURONS

1. Nerve growth factor (NGF) is a member of a family of molecules (the neurotrophins) that can regulate the survival and/or outgrowth of man y vertebrate cells. NGF also induces outgrowth from Lymnaea neurons un der experimental conditions. Recent studies have shown that the neurot rophins can also acutely modulate some physiological properties of adu lt neurons. Here we examined the actions of NGF on high-voltage-activa ted (HVA) Ca2+ currents in Lymnaea motoneurons. 2. NGF induced a dose- dependent and reversible increase in HVA Ca2+ currents within 2 min. 3 . The threshold dose of the NGF-induced enhancement of HVA Ca2+ curren ts ranged between 1 and 1,000 pg/ml. In the most sensitive cells, the response saturated at doses higher than 1 ng/ml. 4. The results indica te that neurotrophins acutely modulate voltage-gated Ca2+ currents in molluscan neurons through a high affinity signal transduction pathway. The data support the existence of neurotrophins in invertebrates. Mor eover, this property of NGF may explain the neuromodulatory actions of neurotrophins ohserved in various preparations.