On the other hand, the late phase of CF elimination has been shown to require the metabotropic glutamate receptor subtype 1 (mGluR1)–to–protein kinase Cγ (PKCγ) cascade in PCs26–31, involves activation of the immediate early geneArc22,32, and is regulated by GABAergic inhibition of the PC soma by basket cells33 (Figure 2). This evidence concerns the gene GRM1 and cystic fibrosis.