N-methyl-D-aspartate receptors in motoneurones after unilateral axotomy in the neonatal rat.
Quantitative autoradiography was used to characterise the binding of the N-methyl-D-aspartate receptor antagonist [3H]dizocilpine maleate in the ventral horns of the lumbar spinal cord of normal, sham-operated, and axotomized neonatal rats. Specific binding sites were revealed on the cell membranes of the motoneurones. In the normal neonate both the Bmax and the Kd values for the binding declined over the first 14 days of life. At 14 days the Kd value was similar to that in adult rats. Unilateral sciatic nerve section was performed in neonates on the day of birth. Axotomy caused the death of approximately 53% of motoneurones. The Bmax and Kd values for [3H]dizocilpine maleate binding declined in the first 2 weeks on operated and contralateral sides in both axotomized and sham-operated animals. However, the specific binding per motoneurone was significantly higher on the sectioned side in axotomized animals at all times examined after the day of birth. The results are consistent with two populations of NMDA receptors with different binding affinities being present in motoneurones at birth, and the lower affinity receptor gradually disappearing over the first few days. The lower affinity receptor may be responsible for the plasticity of motoneurones during embryonic and neonatal life, and for determining which motoneurones die after axotomy.
Hughes
S
S
Department of Physiology, Medical School, University of Birmingham, UK.
Lowrie
M B
MB
Smith
M E
ME
D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D019771:Axotomy; D016291:Dizocilpine Maleate / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000378:metabolism; D007839:Functional Laterality / Q000502:physiology; D008161:Lumbosacral Region; D009046:Motor Neurons / Q000378:metabolism* / Q000648:ultrastructure; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012584:Sciatic Nerve / Q000293:injuries*; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism*; D014316:Tritium
D018691:Excitatory Amino Acid Antagonists; D016194:Receptors, N-Methyl-D-Aspartate; D014316:Tritium; D016291:Dizocilpine Maleate