Expression of brain-derived neurotrophic factor in catecholaminergic neurons of the rat lower brainstem after colchicine treatment or hemorrhage

Widespread brain-derived neurotrophic factor messenger RNA expression has been detected in the region of catecholamine groups of the rat lower brainstem, while few brain-derived neurotrophic factor-immunoreactive cells were found in this area. In the present study, a double-color immunofluorescence technique for brain-derived neurotrophic factor and tyrosine hydroxylase after colchicine treatment was employed to evaluate the possible presence of brain-derived neurotrophic factor immunoreactivity in the catecholaminergic cells of the rat lower brainstem. We detected many new brain-derived neurotrophic factor-immunoreactive cells in the A1, A2, A4, A6- A10 and C1-C3 cell groups and in the other lower brainstem nuclei where, without colchicine treatment, brain-derived neurotrophic factor messenger RNA was expressed, but not brain-derived neurotrophic factor immunoreactivity. In addition, the catecholaminergic neurons were found to express brain-derived neurotrophic factor immunoreactivity with the co-existence being greatest, in percentage terms, in medullary catecholaminergic cell groups. Hypotensive hemorrhage, which activates medullary catecholaminergic neurons, induced the expression of brain-derived neurotrophic factor immunoreactivity in catecholaminergic neurons (A1/C1 and C2). The results demonstrate that brain- derived neurotrophic factor is regulated by neuronal activity in medullary catecholaminergic cell groups involved in central cardiovascular regulation.