Chronic morphine treatment increases the expression of the neural cell adhesion molecule in the dorsal horn of the mouse spinal cord.
It is well known that prolonged exposure to morphine results in tolerance to morphine-induced antinociception. In the present study, we found that mice that were tolerant to morphine-induced antinociception exhibited an increase in immunoreactivity for the neural cell adhesion molecule in the dorsal horn of the spinal cord, which was highly overlapped with immunoreactivity for the increased metabotropic glutamate receptor 5 induced by morphine. These findings support the idea that repeated stimulation of mu-opioid receptors increases the expression of neural cell adhesion molecule and metabotropic glutamate receptor 5. This phenomenon leads to the enhanced excitatory synaptic transmission in the dorsal horn of the spinal cord, and in turn suppresses the morphine-induced antinociception.
Suzuki
Masami
M
Department of Toxicology, Hoshi University School of Pharmacy and Pharmaceutical Sciences, 2-4-41 Ebara, Tokyo 142-8501, Japan.
Narita
Minoru
M
Narita
Michiko
M
Niikura
Keiichi
K
Suzuki
Tsutomu
T
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005786:Gene Expression Regulation / Q000187:drug effects*; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D009020:Morphine / Q000008:administration & dosage*; D009294:Narcotics / Q000008:administration & dosage*; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism*; D020671:Posterior Horn Cells / Q000187:drug effects*; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology*
D009294:Narcotics; D019006:Neural Cell Adhesion Molecules; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D009020:Morphine