Mechanisms of bupivacaine inhibition of glutamate-induced intracellular calcium elevation in primary cultured rat hippocampal astrocytes

This research investigated the mechanism by which bupivacaine inhibits glutamate-induced intracellular free Ca²⁺ increases in primary cultured hippocampal astrocytes. Immunofluorescence was used to demonstrate the expression of metabotropic glutamate receptor (mGluR5 receptor) on neurons and astrocytes. Calcium imaging was used to measure the alteration of intracellular free Ca²⁺ (Ca²⁺_i) in primary cultured rat hippocampal neurons and astrocytes. The animal experiments were approved by the Animal Experiments Ethical Committee of Hebei Medical University. The results showed that mGluR5 receptor was abundantly expressed in the primary cultured rat neurons and astrocytes. Bupivacaine (300 μmol·L^-1) significantly inhibited 1 mmol·L^-1 glutamate-inducedCa²⁺_i increase in astrocytes (P<0.01). 2-Methyl-6-(2-phenylethynyl)-pyridine (MPEP) (10 μmol·L^-1) completely abolished the increase ofCa²⁺_i induced by 1 mmol·L^-1 glutamate in the astrocytes (P<0.01), while the inhibitory effect on neurons was only 10%-20%. Bupivacaine (300 μmol·L^-1) completely inhibited theCa²⁺_i increase induced by mGluR5 receptor agonists (RS)-3,5-dihydroxyphenylglycine (DHPG) (50 μmol·L^-1) and (RS)-2-chloro-5-hydroxyphenylglycine sodium salt (CHPG) (1 mmol·L^-1) in astrocytes (P<0.01). In addition, bupivacaine inhibited the CHPG-inducedCa²⁺_i increase in a dose-dependent manner in astrocytes with an IC₅₀ of 100 μmol·L^-1. The results from this study indicate that bupivacaine inhibits glutamate-inducedCa²⁺_i elevation by acting on the mGluR5 receptor in primary cultured hippocampal astrocytes.