mGluR5-PLCβ4-PKCβ2/PKCγ pathways in hippocampal CA1 pyramidal neurons in pilocarpine model of status epilepticus in mGluR5+/+ mice

While it is generally accepted that phospholipase C (PLC) and protein kinase C (PKC) are down-stream proteins involved in metabotropic glutamate receptor 5 (mGluR5)-related signal transduction, we still do not know which subtype of PLC or PKC is specifically regulated after mGluR5 activation. In the present study in mGluR5 wild-type (mGluR5+/+) mice, we showed induced PKCβ2 or PKCγ expression at the border between the stratum oriens and alveus (O/A border) at 2 h during pilocarpine induced status epilepticus (SE), and in the stratum pyramidale in CA1 area at 1 day after pilocarpine induced SE; at 1 day, induced expression of PLCβ4 in the stratum pyramidale of CA1 area was observed. Furthermore, double labeling revealed the co-localization of induced PKCβ2 or PKCγ with mGluR5 or with induced PLCβ4 in the stratum pyramidale of CA1 area. These induced expression, however, were not found in mGluR5 mutant (mGluR5−/−) mice. It suggests that induced PLCβ4-PKCβ2/PKCγ at 1 day after pilocarpine induced SE in pyramidal neurons or PKCβ2 or PKCγ in interneurons at O/A border at 2 h during pilocarpine induced SE may be specifically linked to the activation of mGluR5. When compared to mGluR5+/+ mice, significant shorter latency (from pilocarpine injection to the occurrence of status epilepticus) and maintenance period (from beginning to the end of status epilepticus) for status epilepticus in mGluR5−/− mice were also demonstrated. It is possible that mGluR5 may play a negative role in initiation of status epilepticus by interacting with muscarinic acetylcholine receptor in mGluR5+/+ mice.