NEUROTRANSMITTERS AND LOCAL CIRCUITS IN SOMESTHESIS

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The proposed research's focus is on the issue of identification of neurotransmitters in a subpopulation of spinal genglia neurons, their central representation, especially at the level of the cuneate nucleus of cats, and the intrinsic circuitry of this nucleus. One of the aims of the research is to identify dorsal ganglion neurons that use glutamate as neurotransmitter, to establish their percentage and whether these are primarily related to cutaneous, muscle or joint afferents. Histochemical, autoradiographic and immunocytochemical techniques will be used and, in most experiments, a combination of more than one approach will be employed in order to doublelabel neurons. The second aim of the research is to study the pattern of arborization, collateralization, termination and the neurotransmitter of individual, electrophysiologically-identified primary afferents from the forelimb into the cuneate nucleus of cats. Also for this general project different experimentl strategies will be employed but the emphasis is on intracellular recording and staining with horseradish peroxidase. The third and final aim of the research is to define, from an investigation on processes that contain glutamic acid decarboxylase and are, therefore, presumed to use GABA as inhibitory neurotransmitter, the intrinsic circuitry of the cuneate n. and to elucidate the anatomical substrate of integrative mechanisms in it. The general goal of the research is to contribute to an understanding of basic functional properties of the somatosensory system in mammals a task that is made especially worth when considering that the bulk of the research on somesthesis is at the level of the thalamus and cerebral cortex. The degree of significance of such a research is by necessity going to be conditioned by the understanding of the mechanisms operating at a pre-thalamic level, i.e. in dorsal column nuclei and spinal cord.