Short-latency drinking and increased Na appetite after intracerebral microinjections of NGF in rats

Abstract

NERVE GROWTH FACTOR (NGF) is a polypeptide trophic factor for peripheral sympathetic and sensory neurones^1,2. Apparent NGF^3–5 and NGF receptors^6,7 have also been identified in the brain, and intracerebral administration of NGF in the adult rat produces marked biochemical⁸ and morphologica^9,10 changes in brain tissue. These findings, taken together with the observations that central injections of NGF facilitate behavioural recovery from brain damage^11,12, indicate that this polypeptide may have an important role in brain function. It has been observed that rats given intraventricular injections of up to 2.3 µg NGF drink copiously (M.E.L. and G. Guroff, unpublished observations). Perkins et al.¹³ reported that diencephalic application of crystalline NGF (1–15 µg) resulted in an intense polydipsia. The present report confirms the observations of M.E.L. and Guroff, and extends the findings of Perkins et al.¹³ by using solutions of NGF instead of crystals. It also describes for the first time a second phenomenon produced by intracranial administration of NGF, namely an intense appetite for aversive concentrations of sodium solutions.