Developmental alterations in thermal nociceptive threshold and the distribution of immunoreactive calcitonin gene-related peptide and substance P after neonatal administration of capsaicin in the rat.
Age-dependent changes in thermal nociceptive threshold, as determined by the hot plate test, occurred in rats treated neonatally with capsaicin. From 4 weeks of age, hot plate latency increased to a maximum at 8 weeks of age and then declined to control values by 16 weeks of age. Although substantially diminished by 10 days of age, calcitonin gene-related peptide (CGRP)-like immunoreactivity increased in laminae I and II between 8 and 16 weeks of age. In addition, a dense plexus of CGRP-like immunoreactive fibers appeared in laminae III and IV. Similar changes in substance P-like immunoreactivity were not observed. The parallel timecourse of these alterations suggests that CGRP is involved in nociceptive processing in the spinal cord.
Hammond
D L
DL
Department of Central Nervous System Diseases Research, G.D. Searle & Co., Skokie, IL 60077.
Ruda
M A
MA
D000375:Aging / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin / Q000494:pharmacology*; D006358:Hot Temperature; D007150:Immunohistochemistry; D009479:Neuropeptides / Q000378:metabolism*; D009619:Nociceptors / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012684:Sensory Thresholds; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D013373:Substance P / Q000378:metabolism*
D009479:Neuropeptides; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide; D002211:Capsaicin