Mobilisation of intracellular Ca2+ by mGluR5 metabotropic glutamate receptor activation in neonatal rat cultured dorsal root ganglia neurones

The ability of metabotropic glutamate receptor activation to mobilise intracellular calcium was investigated in cultured dorsal root ganglion (DRG) neurones from neonatal rats using the calcium sensitive fluorescent dye Fura-2. L-glutamate (10 mu M) caused sustained and oscillatory increases in intracellular calcium concentration ([Ca2+](i)) in a subpopulation of cultured DRG neurones. The oscillatory responses were not blocked by combined application of the ionotropic glutamate receptor antagonists MK 801 (2 mu M) and CNQX (20 mu M) Oscillations in [Ca2+](i) were also observed following application of the nonselective metabotropic glutamate receptor (mGluR) agonist, trans-(1S,3R)-1-aminocyclopentane-1S, 3R-dicarboxylic acid (1S,3R)-ACPD, 20 mu M) and the mGluR, agonist (RS)-2-chloro-5-hydroxyphenylglycine (CHPG, 500 CIM) These responses were blocked by the selective Group I mGluR antagonist (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA) (100 mu M) and Ca2+ release channel inhibitors ryanodine (100 CIM) and dantrolene (10 mu M). The predominantly Group II agonist (2S,2'R,3'R)-2-(2'3'-dicarboxy-cyclopropyl)glycine (DCG-IV, 100 mu M) failed to produce Ga2+ transients alone but suppressed responses to CHPG. Reverse transcriptase PCR techniques, using primers specific to Group I mGluRs, revealed the presence of mGluR, but not mGluR, mRNA in these cells. Therefore, glutamate can cause a slowly activating and reversible mobilisation of [Ca2+], in sensory neurones by activation of ionotropic receptors, and can induce oscillatory calcium transients by selectively activating metabotropic glutamate receptors that are likely to be of the mGluR, subtype. (C) 2000 Elsevier Science Ltd. All rights reserved.