Estradiol attenuates ATP-induced increase of intracellular calcium through group II metabotropic glutamate receptors in rat DRG neurons

摘要

Estradiol attenuates the ATP-induced increase of intracellular calcium concentration ([Ca²⁺]i) in rat dorsal root ganglion (DRG) neurons by blocking the L-type voltage gated calcium channel (VGCC). Since ATP is a putative nociceptive signal, this action may indicate a site of estradiol regulation of pain. In other neurons, 17β-estradiol (E2) has been shown to modulate L-type VGCC through a membrane estrogen receptor-group II metabotropic glutamate receptor (mGluR2/3). The present study investigated whether the rapid estradiol attenuation of ATP-induced increase [Ca²⁺]i requires the mGluR2/3. Previously we showed that DRG (L1-S3) express ERα, P2X3 and mGluR2/3 receptors. DRG were acutely dissociated by enzyme digestion and grown in short-term culture for imaging analysis. DRG neurons were stimulated twice, once with ATP (50 μM) for 5 seconds, and then again in the presence of E2 (100 nM) or E2 (100 nM) + (100nM), an mGluR2/3 inhibitor. ATP induced transient increase in [Ca²⁺]i (216.3 ± 41.2 nM). This transient could be evoked several times in the same DRG neurons if separated by a 5 min washout. Treatment with estradiol significantly attenuated the ATP-induced [Ca²⁺]i in 60% of the DRG neurons, to 163.3±20.9 nM (p<0.001). Co-application of E2 and the mGluR2/3 inhibitor blocked the 17β-estradiol-attenuation of the ATP-induced [Ca²⁺]_i transient (209.1±32.2 nM, p>0.05). These data indicate that the rapid action of E₂ in DRG neurons is dependent on the mGluR_2/3, and demonstrate that membrane estrogen receptor-α initiated signaling involves tan interaction with mGluRs.