THE MARGINAL NUCLEI OF THE SPINAL-CORD IN TURTLES - NEURON ASSEMBLIESIN WHICH GAMMA-AMINOBUTYRIC-ACID AND NITRIC-OXIDE SYNTHASE ARE COLOCALIZED

Conspicuous nerve-cell assemblies, identified as the marginal nuclei d escribed in other sauropsidans, were found all along the spinal cord o f turtles. gamma-aminobutyric acid (GABA) and nitric oxide synthase (N OS) activities were colocalized within these neurons, which also react ed positively to reduced nicotinamide adenine dinucleotide phosphate-d iaphorase stains. The marginal nuclei neurons may, thus, play an inhib itory function mediated by their GABA terminals and a long-distance mo dulatory function mediated by NO liberation.