Immunocytochemical detection of newly generated neurons in the perilesional area of cortical infarcts after intraventricular application of brain-derived neurotrophic factor.

The adult brain responds to focal infarction with proliferation of glial subpopulations. In addition, cells that express the immature neuronal marker doublecortin have been found consistently in the perileisonal zone. We investigated whether application of brain-derived neurotrophic factor (BDNF) would influence this perilesional proliferative response. Photothrombotic infarcts were induced in the sensorimotor forelimb and hindlimb cortex of adult rats. Brain-derived neurotrophic factor or vehicle was continuously infused intraventricularly for 2 weeks after the infarct using osmotic minipumps. Proliferating cells were labeled by daily intraperitoneal injections of bromodeoxyuridine during the first 2 weeks and were quantified at days 14 and 42 using semiautomatic stereology. Triple immunofluorescence with antibodies against immature and mature neuronal and glial markers was used to identify the proliferating cell populations. On day 14 after intraventricular BNDF application, the numbers of doublecortin-positive cells were doubled in the perilesional zone. On day 42, BDNF-treated animals had a small number of mature neurons in these areas, whereas vehicle-treated controls did not. Behavioral analysis with a battery of sensorimotor tests revealed, however, that the alterations in the perilesional cellular response were not associated with an improved functional outcome.