Effect of muscle pain on c-fos expression and NADPH-diaphorase activity in the spinal cord

• Published in: Fiziolohichnyi zhurnal (Kiev, Ukraine : 1994) Ukraine : 1994), 2004, Vol.50 (6), p.62-75
• Main Author: Maznychenko, A V
• Format: Article
• Language: Ukrainian
• Subjects: Animals; Capsaicin - administration & dosage; Capsaicin - pharmacology; Cats; Disease Models, Animal; Immunohistochemistry; NADPH Dehydrogenase - metabolism; Neck Muscles - innervation; Neck Muscles - metabolism; Neural Pathways - metabolism; Neurons - enzymology; Neurons - metabolism; Pain - metabolism; Proto-Oncogene Proteins c-fos - biosynthesis; Spinal Cord - enzymology; Spinal Cord - metabolism
• ISSN: 2522-9028

Capsaicin (Sigma, 5 mg/l ml) was unilaterally injected into dorsal neck muscles (mm. trapezius, splenius) of the cat (n = 6) anesthetized with alpha-chloralose. The laminar distribution of Fos- immunoreactive (Fos-ir) and NADPH-d-reactive neurons was studied in the sections of the cervical and lumbar segments. In comparison to sham operated animals (n = 2), 2 h after capsaicin injection the significant c-fos expression was found throughout the cervical cord (C1 - C8) ipsilaterally and lumbar cord bilaterally (L1 - L7), while the predominant mean number of Fos-ir neurons was detected in the C1 - C4 and L3-L6 segments. In cervical spinal cord, c-fos expression was three times more than in lumbar spinal cord. Dorsal neck noxious stimulation produced widespread c-fos expression in the large and small labeled cells within lamina 1, at the neck of the dorsal horn (lamina V) and also in the medial part of the intermediate zone (lamina VII) where cells of origin of the long crossed and uncrossed descending propriospinal pathways to the lumbar cord were known to be localized. The main accumulations of NADPH-d-reactive cells were registered within the marginal zone (laminae I and II) and medial part of the intermediate zone (lamina VII). Fos-ir neurons were co-distributed with NADPH-d-reactive cells within the marginal zone, and the neck of the dorsal horn, however, double-staining spinal neurons were not registered. These results strongly suggest that the revealed c-fos expression in cervical and lumbar segments depends on the activity of vanilloid receptors of the cervical muscles and confirmed the anatomical coupling of both regions through long propriospinal pathways which may be underlying in the cervico-lumbar nociceptive processing. An influence of the spino-cerebro-spinal loop on modulation c-fos expression in these regions is not excluded also.