DOWN-REGULATION OF METABOTROPIC GLUTAMATE-RECEPTOR 1A IN MOTONEURONS AFTER AXOTOMY

AXOTOMIZED motoneurons display drastic modifications in synaptic struc ture and function related to their disconnection from the periphery an d establishment of a regenerative metabolic functional mode. The molec ular basis of these modifications is not fully understood. Here we des cribe changes in metabotropic glutamate receptor la (mGluR1a)-immunore activity 3, 7 or 14 days after unilateral sciatic transection. mGluR1a -immunoreactivity was distributed throughout the somatic cytoplasm and somatodendritic membrane of uninjured motoneurons and was significant ly reduced in axotomized motoneurons. This reduction was observed at 3 days and grew progressively over 2 weeks. These findings suggest that downregulation of mGluR1a could contribute to reduced excitatory neur otransmission in axotomized motoneurons.