Intrastriatal and intraventricular infusion of brain-derived neurotrophic factor in the cynomologous monkey: distribution, retrograde transport and co-localization with substantia nigra dopamine-containing neurons.

The distribution and retrograde transport of brain-derived neurotrophic factor was examined using magnetic resonance imaging guided stereotaxic intracerebroventricular and intrastriatal infusion in the cynomologous monkey. Two intracerebroventricular animals were infused with brain-derived neurotrophic factor at a dose of 3 micrograms/h for 21 and 28 days. A third intracerebroventricular animal received sequential infusions of 15, 30 and 60 micrograms/h brain-derived neurotrophic factor each for seven days using an Alzet 2002 minipump. For the multiple intrastriatal animals (n = 5) a dose of 3 micrograms/h was infused into each site. One intrastriatal monkey was infused with vehicle solution of 10 mM phosphate-buffered saline pH 7.4 for 14 days resulting in no brain-derived neurotrophic factor immunoreactivity. Following the lower dose intracerebroventricular infusion, brain-derived neurotrophic factor immunoreactivity was confined to the ventricular ependymal layer. In the sequential higher dose intracerebroventricular case, the cannula was located mainly within the lateral ventricle, although there was damage to the ependymal wall and adjacent caudate nucleus. Brain-derived neurotrophic factor immunoreactivity revealed spread of injectate within the ipsilateral and to a lesser extent the contralateral caudate nucleus, septum, orbital cortex and ventricular ependymal wall. In this case, retrogradely labelled brain-derived neurotrophic factor neurons were found within the parafascicular thalamus and substantia nigra, pars compacta, as well as within cortex, vertical limb of the diagonal band and nucleus basalis. Brain-derived neurotrophic factor intrastriatal infusion retrogradely labelled perikarya within sensory motor cortex, parafascicular thelamus and substantia nigra, pars compacta. Sections from these cases dual-immunoreacted for brain-derived neurotrophic factor and tyrosine hydroxylase, the synthesizing enzyme for dopamine, revealed a subpopulation of pars compacta dopaminergic neurons which contained retrogradely transported brain-derived neurotrophic factor. These findings indicate that a select subgroup of nigral dopamine neurons retrogradely transport brain-derived neurotrophic factor in the primate. Furthermore it remains to be determined whether select nigral cells are responsive to the trophic influences of brain-derived neurotrophic factor in the normal and neuropathologic condition.