OPTICAL IMAGING OF DYNAMIC HORIZONTAL SPREAD OF EXCITATION IN RAT AUDITORY-CORTEX SLICES

Optical recordings using a voltage-sensitive dye (RH482) were conducte d in brain slice preparations to investigate spatiotemporal patterns o f excitation in the rat auditory cortex. Electrical stimulation of the border between the white matter and layer VI evoked vertical as well as horizontal spreading responses. While Velocities of vertical and ho rizontal propagation of excitation were similar to those reported in n on-disinhibited preparations, the horizontal propagation was widesprea d and strong especially in layers II/III in auditory cortex slices. Th is horizontal spread was blocked by 6-cyano-7-nitroquinoxaline-2,3-dio ne (CNQX) but not by D-2-amino-5-phosphonopentanoic acid (D-AP5). Thes e results suggest that the horizontal responses, especially in layers II/III, are prominent and are mediated primarily by non-N-methyl-D-asp artic acid (NMDA) receptors in the auditory cortex. (C) 1997 Elsevier Science Ireland Ltd.