A dynamic and quantitative study of pattern visual evoked potentials and gamma-aminobutyric acid neurones in the lateral geniculate nucleus and the visual cortex of monocular deprivation cats.

PURPOSE

To assess the effects of monocular lid closure during critical period on cortical activity.

METHOD

Pattern visual evoked potentials (PVEP) of the normal and the monocular deprivation (MD) cats were dynamically measured and the number of gammaaminobutyric acid immunopositive (GABA-IP) neurones of the area 17 of the visual cortex and the lateral geniculate nucleus (LGN) was quantitatively compared by using immunohistochemical method (ABC).

RESULTS

The amplitude of the N1-P1 attenuated in deprived eyes (DE), NE/DE at postnatal week (PNW) 7-8 (P < 0.05), NE/DE at PNW 15-16 (P < 0.01); while P1 latency delayed, NE/DE at PNW 7-8 (P > 0.05), NE/DE at PNW 15-16 (P< 0.05). The numbers of GABA-IP neurones in layer A1 of the ipsilateral LGN and in layer A of the contralateral LGN, compared to those in the corresponding normal laminae, were not significant at PNW 7-8 and PNW 11-12 (P > 0.05), while in the same cats a reduction in the number of GABA-IP neurones was found in layer IV of area 17 at PNW 11-12 (P < 0.05). However, with longer survival of 3-4 weeks in duration, the numbers of GABA-IP neurones in the deprived laminae of LGN were remarkably reduced (P < 0.05).

CONCLUSIONS

The amplitude of N1-P1 components is sensitive to the effects of monocular deprivation. Monocular deprivation in cats during critical period leads to dramatic changes of the number of GABA-IP neurones in the LGN and cortical layer IV receiving inputs from the deprived eye in cats. The deprivation-induced reduction in GABA-IP neurones is delayed in the LGN compared with the visual cortex. PVEP of the MD cats is consistent with the damage of its GABA system in visual cortex.