MESSENGER-RNAS CODING FOR NEUROTRANSMITTER RECEPTORS AND VOLTAGE-GATED SODIUM-CHANNELS IN THE ADULT-RABBIT VISUAL-CORTEX AFTER MONOCULAR DEAFFERENTIATION

It has been postulated that, in the adult visual cortex, visual inputs modulate levels of mRNAs coding for neurotransmitter receptors in an activity-dependent manner, To investigate this possibility, we perform ed a monocular enucleation in adult rabbits and, 15 days later, collec ted their left and right visual cortices, Levels of mRNAs coding for v oltage-activated sodium channels, and for receptors for alpha-amino-3- hydroxy-5-methylisoxazol-4-propionic acid (AMPA), N-methyl-D-aspartate (NMDA), gamma-aminobutyric acid (GABA), and glycine were semiquantita tively estimated in the visual cortices ipsilateral and contralateral to the lesion by the Xenopus oocyte/voltage-clamp expression system. T his technique also allowed us to study some of the pharmacological and physiological properties of the channels and receptors expressed in t he oocytes, In cells injected with mRNA from left of right cortices of monocularly enucleated and control animals, the amplitudes of current s elicited by kainate or AMPA, which reflect the abundance of mRNAs co ding for kainate and AMPA receptors, were similar, There was no differ ence in the sensitivity to kainate and in the voltage dependence of th e kainate response, Responses mediated by NMDA, GABA, and glycine were unaffected by monocular enucleation. Sodium channel peak currents, ac tivation, steady-state inactivation, and sensitivity to tetrodotoxin a lso remained unchanged after the enucleation, Our data show that mRNAs for major neurotransmitter receptors and ion channels in the adult ra bbit visual cortex are not obviously modified by monocular deafferenti ation. Thus, our results do not support the idea of a widespread dynam ic modulation of mRNAs coding for receptors and ion channels by visual activity in the rabbit visual system.