Attenuation of naloxone-induced Vc pERK hyper-expression following capsaicin stimulation of the face in aged rat.
In order to clarify the effect of age-related change in trigeminal nociception, phosphorylation of extracellular signal-regulated kinase (pERK) in trigeminal spinal subnucleus caudalis (Vc) and upper cervical spinal cord neurons were studied in the aged rats following subcutaneous capsaicin injection into the whisker pad. A large number of pERK-LI cells was expressed in the superficial laminae of Vc and upper cervical spinal cord in adult and aged rats following subcutaneous capsaicin injection into the whisker pad region. The number of pERK-LI cells was largest at about 2.0mm caudal from the obex and gradually decreased in their numbers in more rostral and caudal sections. The rostro-caudal distribution profile of pERK-LI cells expressed after subcutaneous capsaicin injection into whisker pad was similar in adult and aged rats. The number of pERK-LI cells was slightly, but not significantly larger in aged rats compared with that of adults. Pretreatment with naloxone significantly increased the number of capsaicin-induced pERK-LI cells in adult rats but not in aged rats. The present findings suggest that the descending modulation system impaired with advancing age, resulting in the abnormal pain sensation in aged rats.
Suzuki
Ikuko
I
Department of Physiology, School of Dentistry, Nihon University, 1-8-13 Kandasurugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
Kitagawa
Junichi
J
Noma
Noboru
N
Tsuboi
Yoshiyuki
Y
Kondo
Masahiro
M
Honda
Kuniya
K
Kanda
Kenro
K
Hasegawa
Momoko
M
Saito
Kazunobu
K
Okamoto
Ryuzo
R
Iwata
Koichi
K
D000375:Aging / Q000502:physiology*; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects* / Q000378:metabolism; D005145:Face / Q000294:innervation; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009434:Neural Pathways / Q000187:drug effects / Q000503:physiopathology; D010146:Pain / Q000503:physiopathology*; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D011916:Rats, Inbred F344; D018689:Sensory System Agents / Q000494:pharmacology; D014275:Trigeminal Caudal Nucleus / Q000187:drug effects / Q000378:metabolism
D009292:Narcotic Antagonists; D018689:Sensory System Agents; D009270:Naloxone; D048049:Extracellular Signal-Regulated MAP Kinases; D002211:Capsaicin