Brain-derived neurotrophic factor messenger RNA is expressed in the septum, hypothalamus and in adrenergic brain stem nuclei of adult rat brain and is increased by osmotic stimulation in the paraventricular nucleus.

We have detected scattered brain-derived neurotrophic factor mRNA-producing neurons in the medial septal nucleus, which contains cholinergic neurons that are responsive to brain-derived neurotrophic factor and nerve growth factor. In the brainstem, many adrenergic neurons showed a positive signal for brain-derived neurotrophic factor messenger RNA. Several hypothalamic nuclei contain brain-derived neurotrophic factor messenger RNA-positive neurons, among them paraventricular, median preoptic, vetromedial and dorsomedial nuclei. Osmotic stimulus, which activates vasopressin-producing neurons increased brain-derived neurotrophic factor messenger RNA levels in the paraventricular nucleus demonstrating that this factor is regulated by neuronal activity not only in the hippocampus and cortex but also in the hypothalamus.