Capsaicin-induced neuronal degeneration: silver impregnation of cell bodies, axons, and terminals in the central nervous system of the adult rat.

摘要: Capsaicin is a neurotoxic substance valued in neurobiological research because of its ability to selectively damage small unmyelinated primary sensory neurons. Previous work has indicated that systemic capsaicin administration causes permanent neuronal degeneration neonatal rats, but evidence similar effect adults equivocal and incomplete. Therefore, we used silver impregnation, method labels degenerating neurons, examine the central nervous system adult rats after treatment. Adult were injected with single intraperitoneal dose (50 or 90 mg/kg) vehicle solution killed 6, 12, 18, 24, 48, 96, 240 hours later. Sections brain spinal cord stained Carlsen-de Olmos cupric method. As reported previously, sections revealed areas known be innervated by small-diameter fibers: substantia gelatinosa dorsal horn trigeminal nucleus, solitary nucleus tract, lateral borders area postrema. In addition, axon terminal was observed several discrete forebrain hindbrain not previously associated capsaicin-induced either rats: inferior olive, olivary pretectal interpeduncular suprachiasmatic septum/medial accumbens region. Furthermore, cell bodies intrafascicular ventromedial midbrain tegmentum, supramammillary posterior hypothalamic area. Unilateral nodose ganglionectomy produced staining on denervated side very induced bilaterally capsaicin. unilateral 1 month prior injection greatly attenuated ipsilateral confirming hypothesis damages vagal neurons innervating this nucleus. Capsaicin-induced long-lasting, since second two treatments spaced 4.5 months apart no additional degeneration.