Expression of trkA and p75 nerve growth factor receptors in the adrenal gland.

High and low affinity nerve growth factor (NGF) receptors were localized to specific cells and processes within the adult rat adrenal gland. Protein immunoreactivity and mRNA for high affinity trkA receptors were found in a subpopulation of adrenergic chromaffin cells and the clustered ganglion cells which do not express nitric oxide synthase (NOS). These ganglion cells, a subpopulation of the NOS containing ganglion cells, and all chromaffin cells were immunoreactive for p75, the low affinity neurotrophin receptor. TrkA immunoreactivity was found in ganglion cell processes and in sensory innervation but not preganglionic sympathetic innervation. The overlapping but distinct patterns of trkA and p75 expression provide a basis for differential actions of neurotrophins within the adrenal gland.