Stimulation of growth of new axonal sprouts from lesioned monoamine neurones in adult rat brain by nerve growth factor

Abstract

A strong stimulating effect of intraventricularly administered NGF proteins has been demonstrated on the growth of new axonal sprouts from lesioned central catecholamine and indolamine neurones in the adult rat. The effect was observed as an increase in the growth of the lesioned ascending noradrenaline, dopamine, and indolamine neurone systems into a denervated iris transplanted to the caudal diencephalon. The response was similar with high molecular (7S) and low molecular (2.5S and the β-subunit of 7S NGF) NGF preparations, and it was dose-dependent. The results suggest that NGF, given as a single injection at the time of transplantation and axonal lesioning, did not alter the time sequence of events in the growth process ( i.e. the time necessary for the initiation of sprouting) but rather that it accelerated or potentiated the outgrowth of the new axonal sprouts during the time when it normally occurred. It is suggested that the NGF sensitivity of regenerating central noradrenaline, dopamine, and indolamine neurones might reflect a general dependence of these neurones on endogenous NGF during ontogenesis and regeneration.