ABSTRACT
BDNF is a protein that allows the survival and differentiation of the central nervous system. In the present study, we have examined the postnatal development of BDNF -immunoreactive (IR) neuron system in the forebrain and the upper brain stem of the rat using immunohistochemistry. In the piriform cortex, claustrum, CA2 and 3, anterodorsal and paraventricular thalamic nucleus (nu.), ventromedial hypothalamic nu. and substantia nigra, BDNF-IR neurons were detected at postnatal day 1. BDNF-IR neurons in the anterior olfactory n., layers V and VI of the neocortex, claustrum, dentate gyrus, basolateral amygdaloid nu., paraventricular hypothalamic nu., mammillary nu. first appeared at postnatal 1 week of age and tended to increase in number as the rats grew. BDNF -IR neurons in ventromedial and paraventricular hypothalamic nu., mammillary nu., and substantia nigra decreased in number and none or only a few BDNF-IR neurons were seen in these areas of the adult rats. However, after treatment of colchicine, these areas showed numerous BDNF-IR neurons. BDNF-IR axon terminals were found in the septal nu., central amygdaloid nu., bed nu., of the stria terminalis, anterior ventral, anterior medial, interanteromedial and paravertricular thalamic nu., at postnatal day 1 and in dentate gyrus and paraventricular hypothalamic nu., at 1 week of age, respectively. These terminals in general continued to increase in number as the rats grew. Our results showed that BDNF immunoreactivity increased in various regions of the postnatally developing rat brain and suggest that BDNF might play an important role in neuronal maturation.