The distribution of glutamic acid, a transmitter candidate, and other amino acids in the dorsal sensory neuron of the cat

Abstract

The distribution of free glutamate in the dorsal sensory neurons is consistent with both a transmitter role and a metabolic role for this substance in the dorsal root projections to the neurons in the spinal grey and primary sensory nuclei of the medulla. There is more free glutamate in the dorsal root or dorsal root ganglion than in the distal sensory root. These data indicate that there must be a differential flow mechanism in the dorsal sensory neuron directing more free glutamate towards the cord where synaptic contacts are made. Free glutamate levels are highest in regions of dorsal root termination. Although the dorsal root ganglion appears to be much like central grey tissue in total free amino acid content, there are differences in levels of individual amino acids between cortical grey, spinal grey, and the dorsal root ganglion. Glutamine levels were highest in the dorsal root ganglion. Several other amino acids also were higher in the dorsal root ganglion than in the dorsal root tissue.