THE DISTRIBUTION OF NEUROTROPHIN RECEPTOR TRKC-LIKE IMMUNOREACTIVE FIBERS AND VARICOSITIES IN THE RHESUS-MONKEY BRAIN

The distribution of immunoreactivity for the neurotrophin receptor tyr osine kinase TrkC was examined in the brain of the adult rhesus monkey . TrkC-like immunoreactivity was widespread and consisted primarily of varicose fibers. The most dense populations of fibers were in the bas al forebrain (in the cholinergic cell groups Ch1, Ch2 and Ch4), in the raphe complex throughout its rostrocaudal extent, and in the locus co eruleus. Other fibers were present in the thalamus, hypothalamus, cent ral gray matter of the midbrain, dorsal midline of the brainstem and t he cerebral cortex. The only neuronal cell bodies with consistent labe ling were located in the lateral hypothalamus. Purkinje cells in the c erebellum showed variable labeling. Specific labeling of varicosities and cell bodies was abolished by omission of the primary antiserum or by preabsorption with the TrkC peptide antigen. We conclude that TrkC- like immunoreactivity can be detected in a wide variety of subcortical locations in the adult rhesus monkey. Labeling was particularly promi nent in the vicinity of the major cholinergic, serotonergic and adrene rgic nuclei, known from other studies to be vulnerable in the ageing b rain. This suggests that the ligand for TrkC, neurotrophin-3, may pers ist as a survival factor for critical neurons into adulthood. (C) 1998 IBRO. Published by Elsevier Science Ltd.