Abstracts

Rationale: TRPC6 is a Ca2+-permeable non-selective cation channel expressed in the molecular layer of the dentate gyrus (DGML) in the hippocampus. TRPC6 activation has been linked to dendritic growth and seems to be a key player in the formation of excitatory synapses. Temporal lobe epilepsy (TLE) involves functional changes to the dentate gyrus, including mossy fiber sprouting, hilar cell loss, interneuronal loss, and aberrant granule cell proliferation and development. With this study we therefore sought to determine how TRPC6 expression is affected in the pilocarpine mouse model of TLE. Methods: Age matched male mice were injected i.p. with 300 mg/kg pilocarpine following injection of 1mg/kg scopolamine. Mice were kept in status epilepticus for 2 hours, and then administered 10 mg/kg diazepam. Mice were intracardially perfused with 4% PFA and brains sectioned at 35 μm, then stained with a primary antibody specific for TRPC6 (Alomone Labs). Results: Optical density of bright field images was assessed with ImageJ and different groups compared with one-way ANOVA. TRPC6 expression levels and pattern were thus determined. Brains were processed at different time points after pilocarpine induced status epilepticus: 1 day, 7 days, and 8 weeks.Our findings show a significant TRPC6 staining reduction in the DGML of the 7 day group, with no changes detected at 1 day or after 8 weeks. Epileptogenesis was confirmed in the 8-week group by the presence of mossy fiber sprouting. Mossy fiber boutons were labeled for zinc transporter 3 and sprouting was detected in the inner DGML. Neuronal cell loss was confirmed with NeuN stain. Conclusions: These results provide evidence regarding TRPC6 modulation during epileptogenesis of TLE and open further questions on the functional consequences of its reduction. Due to its association with excitatory synapses, TRPC6 down regulation may be a neuroprotective mechanism during the epileptogenic process. Drug based activation or inhibition of TRPC6 could lead to future clinical applications in TLE.