A hydrochloride salt obtained by reaction of 2-methyl-6-(phenylethynyl)pyridine with one equivalent of hydrochloric acid. Potent and highly selective non-competitive antagonist at the mGlu5 receptor subtype (IC50 = 36 nM) and a positive allosteric modulator at mGlu4 receptors. Centrally active following systemic administration in vivo. Reverses mechanical hyperalgesia in the inflamed rat hind paw.