MORPHOMETRIC STUDY OF GLYCINE-IMMUNOREACTIVE NEURONS AND TERMINALS INTHE RAT CUNEATE NUCLEUS

The distribution of glycine-immunoreactive (glycine-IR:) neurons and t heir associated axon terminals in the rat cuneate nucleus was studied using antiglycine postembedding immunoperoxidase labelling and immunog old staining, respectively. The immunoperoxidase-labelled glycine-IR n eurons were widely distributed in the entire rostrocaudal extent of th e nucleus. They made up 30.8% (9671/31368) of the neurons surveyed. Qu antitative evaluation showed that the percentage of glycine-IR neurons in the caudal level was significantly higher than that in the middle and rostral levels. The glycine-IR neurons were small cells (mean area = 198 +/- 1.9 mu m(2), n = 2862) with ovoid or spindle-shaped somata. Statistical analysis showed that the size of the glycine-IR neurons i n the rostral level was significantly smaller than that in the middle and caudal levels. Immunogold labelled glycine-IR terminals which cont ained predominantly pleomorphic synaptic vesicles were mostly small (m ean area = 1.24 +/- 0.03 mu m(2), n = 286) and they constituted 24.7% (286/1158) of the total terminals surveyed. They formed axodendritic, axosomatic and axoaxonic synapses with unlabelled elements. It is sugg ested from this study that glycine is one of the major neurotransmitte rs involved in the depression of synaptic transmission in the cuneate nucleus.