NITRIC OXIDE-STIMULATED INCREASE IN INTRACELLULAR CGMP MODULATES GAP JUNCTION COUPLING IN RAT NEOCORTEX

IN the present study we demonstrate that gap junction coupling between developing layer II/III pyramidal cells in rat sensorimotor cortex is strongly modified by the nitric oxide (NO)/cyclic guanosine monophosp hate (cGMP) system. Dye coupling was revealed by intracellular injecti on of the gap junction-permeable tracer neurobiotin into single neuron es. Following incubation of slices with sodium nitroprusside, a source of NO, the size of dye-coupled cell clusters was significantly reduce d. In many cases, 2-3 cells remained strongly dye-coupled. These effec ts were blocked by intracellular injection of the guanylyl cyclase inh ibitor cystamine and mimicked by both application of the membrane-perm eant cGMP analogue 8-Br-cGMP and intracellular injection of cGMP. cGMP injection also induced a 60% increase in neuronal input resistance. T hese results indicate that NO modulates gap junction coupling in the d eveloping neocortex via stimulation of guanylyl cyclase.