Effect of sympathectomy on the expression of NMDA receptors in the spinal cord.
The expression of NMDA receptors in the intermediolateral (IML) region of the upper thoracic spinal cord, was studied in 3 week old rats. The effect of section of the cervical sympathetic nerve on neuronal cell number and receptor expression was examined up to two weeks after the operation. Age-matched sham-operated and unoperated animals were used as controls. It was shown using quantitative autoradiography with the NMDA receptor antagonist [(3)H]MK-801 (dizocilpine maleate), that there was a marked downregulation of receptors in all groups of animals, beginning at approximately 4 weeks of age. However after sympathectomy, which resulted in the death of 44% of neurones in the IML by 7 days, there was a significant increase in receptor density per neurone compared to sham-operated controls. In the control animals there was a significant increase in the Kd value of the binding between 21 and 24 days after birth indicating an increased expression of a low affinity receptor, but no such increase was seen after axotomy. The results are consistent with two populations of NMDA receptors being transiently expressed in the IML in developing animals, and the higher affinity receptor being down-regulated between 4 and 5 weeks of age. The presence of the high affinity receptor subtype may predispose neurones to die after axotomy.
Young
M M
MM
Department of Physiology, The Medical School, University of Birmingham, Birmingham, UK.
Smith
M E
ME
Coote
J H
JH
D000818:Animals; D002452:Cell Count; D002572:Cervical Plexus / Q000601:surgery*; D016291:Dizocilpine Maleate / Q000378:metabolism*; D018691:Excitatory Amino Acid Antagonists / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism* / Q000601:surgery; D013562:Sympathectomy; D013904:Thoracic Vertebrae / Q000601:surgery
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate