SHORT-TERM MODULATION OF GLUTAMATERGIC SYNAPSES IN ADULT-RAT HIPPOCAMPUS BY NGF

NERVE growth factor promotes survival and differentiation of selected groups of neurones through long-term adaptive changes in cell function. While production of this neurotrophin in target cells in hippocampus is regulated in part by afferent glutamate neuronal input, we report now for the first time that nerve growth factor has a direct potentiating effect on spontaneous and depolarization-evoked release of glutamate from hippocampal nerve endings, accompanied by an increase in the excitatory postsynaptic potential of CA1 neurones. This correlated with increased incorporation of [P-32]phosphate into synapsin I. Reciprocal positive feedback between production of trophic factors in target cells by neurotransmitter released from afferent neuronal inputs and the modulation of presynaptic neurotransmitter release by target-derived trophic factors provides a novel mechanism for shortterm control over synaptic communication.