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Effect of chronic inflammation on dorsal horn nociceptive neurons in aged rats.
J Neurophysiol. 2005 Jun; 93(6):3594-604.JN

Abstract

To elucidate the effect of chronic inflammation on spinal nociceptive neurons in the elderly, we compared nocifensive behavior, peripheral inflammatory responses, and spinal dorsal horn neuronal activities between the aged (29-34 mo) and adult (7-12 mo) male rats after injection of complete Freund's adjuvant (CFA) into the hind paw. Aged rats exhibited a significantly lower mechanical paw withdrawal threshold before inflammation. However, after CFA injection mechanical allodynia developed in both adult and aged rats after CFA injection. The changes of foot temperature and thickness after CFA injection were greater and lasted longer in aged than in adult rats. Sets of 124 wide dynamic range (WDR) neurons (aged: 59, adult: 65) and 26 nociceptive specific (NS) neurons (aged: 13, adult: 13) were recorded from the lumber spinal dorsal horn. NS neurons from the inflamed adult rats showed significantly higher responses to noxious mechanical stimulation than those in aged rats, whereas WDR neurons from inflamed adult and aged rats were similar. Background activity of WDR neurons from the adult rats increased after CFA, whereas WDR neurons of aged rats and NS neurons from either group were not. The afterdischarge followed by noxious mechanical stimulation was significantly greater for WDR neurons in both adult and aged rats, whereas no significant differences were observed in NS neurons. Two days after CFA injection, Fos expression increased similarly in aged and adult rats. Thus the aged rats showed enhanced peripheral inflammatory responses to CFA injection with only a slight change in dorsal horn neuronal activity. Together with our previous finding that nociceptive neurons in aged rats exhibit hyperexcitability, these results suggest that the dorsal horn nociceptive system becomes sensitized with advancing age and its excitability cannot be further increased by inflammation.

Authors+Show Affiliations

Department of Physiology, School of Dentistry, Nihon University, 1-8-13 Kandasurugadai, Chiyoda-ku Tokyo, 101-8310, Japan.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15659525

Citation

Kitagawa, Junichi, et al. "Effect of Chronic Inflammation On Dorsal Horn Nociceptive Neurons in Aged Rats." Journal of Neurophysiology, vol. 93, no. 6, 2005, pp. 3594-604.
Kitagawa J, Kanda K, Sugiura M, et al. Effect of chronic inflammation on dorsal horn nociceptive neurons in aged rats. J Neurophysiol. 2005;93(6):3594-604.
Kitagawa, J., Kanda, K., Sugiura, M., Tsuboi, Y., Ogawa, A., Shimizu, K., Koyama, N., Kamo, H., Watanabe, T., Ren, K., & Iwata, K. (2005). Effect of chronic inflammation on dorsal horn nociceptive neurons in aged rats. Journal of Neurophysiology, 93(6), 3594-604.
Kitagawa J, et al. Effect of Chronic Inflammation On Dorsal Horn Nociceptive Neurons in Aged Rats. J Neurophysiol. 2005;93(6):3594-604. PubMed PMID: 15659525.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of chronic inflammation on dorsal horn nociceptive neurons in aged rats. AU - Kitagawa,Junichi, AU - Kanda,Kenro, AU - Sugiura,Miho, AU - Tsuboi,Yoshiyuki, AU - Ogawa,Akiko, AU - Shimizu,Kohei, AU - Koyama,Natsu, AU - Kamo,Hiroshi, AU - Watanabe,Tatsuhisa, AU - Ren,Ke, AU - Iwata,Koichi, Y1 - 2005/01/19/ PY - 2005/1/22/pubmed PY - 2005/7/16/medline PY - 2005/1/22/entrez SP - 3594 EP - 604 JF - Journal of neurophysiology JO - J Neurophysiol VL - 93 IS - 6 N2 - To elucidate the effect of chronic inflammation on spinal nociceptive neurons in the elderly, we compared nocifensive behavior, peripheral inflammatory responses, and spinal dorsal horn neuronal activities between the aged (29-34 mo) and adult (7-12 mo) male rats after injection of complete Freund's adjuvant (CFA) into the hind paw. Aged rats exhibited a significantly lower mechanical paw withdrawal threshold before inflammation. However, after CFA injection mechanical allodynia developed in both adult and aged rats after CFA injection. The changes of foot temperature and thickness after CFA injection were greater and lasted longer in aged than in adult rats. Sets of 124 wide dynamic range (WDR) neurons (aged: 59, adult: 65) and 26 nociceptive specific (NS) neurons (aged: 13, adult: 13) were recorded from the lumber spinal dorsal horn. NS neurons from the inflamed adult rats showed significantly higher responses to noxious mechanical stimulation than those in aged rats, whereas WDR neurons from inflamed adult and aged rats were similar. Background activity of WDR neurons from the adult rats increased after CFA, whereas WDR neurons of aged rats and NS neurons from either group were not. The afterdischarge followed by noxious mechanical stimulation was significantly greater for WDR neurons in both adult and aged rats, whereas no significant differences were observed in NS neurons. Two days after CFA injection, Fos expression increased similarly in aged and adult rats. Thus the aged rats showed enhanced peripheral inflammatory responses to CFA injection with only a slight change in dorsal horn neuronal activity. Together with our previous finding that nociceptive neurons in aged rats exhibit hyperexcitability, these results suggest that the dorsal horn nociceptive system becomes sensitized with advancing age and its excitability cannot be further increased by inflammation. SN - 0022-3077 UR - https://www.unboundmedicine.com/medline/citation/15659525/Effect_of_chronic_inflammation_on_dorsal_horn_nociceptive_neurons_in_aged_rats_ L2 - https://journals.physiology.org/doi/10.1152/jn.01075.2004?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -