Axotomized motoneurons display drastic modifications in synaptic structure and function related to their disconnection from the periphery and establishment of a regenerative metabolic functional mode. The molecular basis of these modifications is not fully understood. Here we describe changes in metabotropic glutamate receptor 1a (mGluR1a)-immunoreactivity 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 significantly 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 neurotransmission in axotomized motoneurons.