- The mGluR5 antagonist 6-methyl-2-(phenylethynyl)pyridine decreases ethanol consumption via a protein kinase C epsilon-dependent mechanism. Olive, M.F., McGeehan, A.J., Kinder, J.R., McMahon, T., Hodge, C.W., Janak, P.H., Messing, R.O. Mol. Pharmacol. (2005)