a , Measurements of PI hydrolysis stimulated by 100 µM ACPD in untransfected PC12 cells, and in PC 12 cells transfected with either mGlu1 or mGlu5 receptors show similar levels of functional receptor expression in mGlu1 and mGlu5-expressing cells. b, Serum deprivation (48 h) decreases viability only in mGlu1-expressing PC12 cells. This is counteracted by the addition of 1 mM glutamate, and is mimicked by 300 µM CPCCOEt, but not by 10 µM MPEP, 1 µM MK801 or 10 µM NBQX. Data shown are means with error bars representing S.E.M. from three independent experiments. **p<0.001 as compared to untransfected cells (a) or to serum containing controls (b) using Student’s t-test.