Metabotropic glutamate receptor/phospholipase C pathway is increased in rat brain at the end of pregnancy

Wistar pregnant rats were sacrificed at the end of pregnancy and the status of metabotropic glutamate receptors/phospholipase C (mGluR/PLC) pathway was studied in brain from pregnant and non-pregnant female rats. Pregnancy causes a significant increase in metabotropic glutamate receptors number, determined by radioligand binding assay, without significant changes on receptor affinity. Similar increase in mGluR1 type was obtained by immunoblotting assay using specific anti-mGluR1 antibody. However, no significant differences were observed in mGluR5 type, suggesting that the increase detected by radioligand assays could be due to mGluR1 up-regulation. On the other hand, a significant increase in the α subunit of Gq protein was also detected in pregnant rats by immunoblotting assays. Real-time PCR experiments revealed a significant increase in gene expression of metabotropic glutamate receptors and Gq proteins. Neither protein level nor gene expression of phospholipase C β1 isoform was altered in pregnant rats. However, an increase in basal and agonist-stimulated phospholipase C activity was observed in membranes from pregnant rats. These results suggest that gestational period causes the up-regulation of both metabotropic glutamate receptors and coupled Gq-protein and, in turn, an increase in phospholipase C activity.