7-Nitroindazole potentiates c-fos expression induced by muscle tendon vibration in the spinal cord.

Introduction: Expression of c-fos initiated by muscle proprioceptive signaling was studied in rats after inhibition of neuronal nitric oxide synthase (nNOS) with administration of 7-nitroindazole (7-NI).
Methods: Fos-immunoreactive (Fos-ir) neurons were visualized immunohistochemically in the lumbar cord after vibration of the Achilles tendon and/or 7-NI systemic injections.
Results: The total number of Fos-ir interneurons and motoneurons (per slice) was significantly greater in the 7-NI-pretreated and tendon-vibrated (7-NI + Tv) group than in the isolated tendon vibration group (Tv group). The greatest increases in the number of Fos-ir neurons were found in the L4 (+100%) and L5 (+105%) segments (P < 0.05).
Conclusions: Suppression of NO release after introduction of 7-NI was associated with potentiation of Fos immunoreactivity induced by muscle proprioceptive signaling within distinctive regions of the spinal cord.
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