AN UNUSUAL EFFECT OF APPLICATION OF THE AMINO-ACID L-ARGININE ON CAT VISUAL CORTICAL-CELLS

IONTOPHORETIC application of L-arginine (L-Arg) resulted in a profound decrease in visually elicited and spontaneous activity in 22 of 77 (2 9%) cells in area 17 of the anaesthetized/paralysed cat. Duration was long, and cells did not recover pre-application activity levels, indic ating permanent decline. This effect was obtained without change in th e extracellularly recorded waveform, demonstrating that this did not r esult from depolarization block. In the remaining 55 cells, applicatio n of L-Arg alone, at levels capable of eliciting inhibition as describ ed above, was without effect. In 29 cells, L-Arg application was able to reverse the effect of inhibition of nitric oxide (NO) production. P opulations of cells showing the depressive effect described above and those affected by NO modulation levels were mutually exclusive.