CARBACHOL MIMICS EFFECTS OF SENSORY INPUT ON TYROSINE PHOSPHORYLATIONIN CORTEX

WE have recently shown that in the gustatory cortex of the rat, taste learning enhances protein tyrosine phosphorylation and taste memory is blocked by muscarinic antagonists. A major protein whose tyrosine pho sphorylation is stimulated by taste learning in cortex is a 180 kDa sy naptic glycoprotein identified as the NMDA receptor subunit 2B (NR2B). Here we report that microinjection of carbachol into the taste cortex modulates protein tyrosine phosphorylation similarly to the effect of unfamiliar taste, and that a 180 kDa protein whose tyrosine phosphory lation is enhanced in vivo by carbachol is NR2B. These data, combined with our previous findings, are in line with the hypothesis that musca rinic input plays a role in encoding new items in memory, and that tyr osine phosphorylation of NR2B is involved in this process.