Canonical transient receptor potential channels (TRPCs) are receptor-operated cation channels that are activated in response to phospholipase C signaling. Although TRPC1 is ubiquitously expressed in the brain, TRPC4 expression is the most restrictive, with the highest expression level limited to the lateral septum. The subunit composition of neuronal TRPC channels remains uncertain because of conflicting data from recombinant expression systems. Here we report that the large depolarizing plateau potential that underlies the epileptiform burst firing induced by metabotropic glutamate receptor agonists in lateral septal neurons was completely abolished in TRPC1/4 double-knockout mice, and was abolished in 74% of lateral septal neurons in TRPC1 knockout mice. Furthermore, neuronal cell death in the lateral septum and the cornu ammonis 1 region of hippocampus after pilocarpine-induced severe seizures was significantly ameliorated in TRPC1/4 double-knockout mice. Our data suggest that both TRPC1 and TRPC4 are essential for an intrinsic membrane conductance mediating the plateau potential in lateral septal neurons, possibly as heteromeric channels. Moreover, excitotoxic neuronal cell death, an underlying process for many neurological diseases, is not mediated merely by ionotropic glutamate receptors but also by heteromeric TRPC channels activated by metabotropic glutamate receptors. TRPC channels could be an unsuspected but critical molecular target for clinical intervention for excitotoxicity.

Summary Objective Canonical transient receptor potential (TRPC) channels constitute a family of cation channels that exhibit a regional and cell-specific expression pattern throughout the brain. It has been reported previously that TRPC3 channels are effectors of the BDNF/trkB signaling pathway. Given the long postulated role of BDNF in epileptogenesis, TRPC3 channels may be a critical component in the underlying pathophysiology of seizure and epilepsy. In this study, we investigated the precise role of TRPC3 channels in pilocarpine-induced Status Epilepticus (SE). Methods The role of TRPC3 channels was investigated using TRPC3 knockout (KO) mice and TRPC3-selective inhibitor Pyr3. Video and EEG recording of pilocarpine-induced seizures were performed. Results We found that genetic ablation of TRPC3 channels reduces behavioral manifestations of seizures and the root-mean-square (RMS) power of SE, indicating a significant contribution of TRPC3 channels to pilocarpine-induced SE. Furthermore, the reduction in SE in TRPC3KO mice is caused by a selective attenuation of pilocarpine-induced theta activity which dominates both the pre-ictal phase and SE phase. Pyr3 also caused a reduction in the overall RMS power of pilocarpine-induced SE and a selective reduction in the theta activity during SE. Significance Our results demonstrate that TRPC3 channels unequivocally contribute to pilocarpine-induced SE and could be a novel molecular target for new anti-convulsive drugs.

PCC activity is the most sensitive indicator of biotin status tested to date. In future pregnancy studies, the use of lymphocyte PCC activity data should prove valuable in the assessment of biotin status.

This article describes the discovery and development of the first highly selective, small molecule antagonist of the muscarinic acetylcholine receptor subtype I (mAChR1 or M1). An M1 functional, cell-based calcium-mobilization assay identified three distinct chemical series with initial selectivity for M1 versus M4. An iterative parallel synthesis approach was employed to optimize all three series in parallel, which led to the development of novel microwave-assisted chemistry and provided important take home lessons for probe development projects. Ultimately, this effort produced VU0255035, a potent (IC50 = 130 nM) and selective (>75-fold vs. M2-M5 and > 10 μM vs. a panel of 75 GPCRs, ion channels and transporters) small molecule M1 antagonist. Further profiling demonstrated that VU0255035 was centrally penetrant (BrainAUC/PlasmaAUC of 0.48) and active in vivo, rendering it acceptable as both an in vitro and in vivo MLSCN/ MLPCN probe molecule for studying and dissecting M1 function.

Background: Marginal biotin deficiency may be a human teratogen. A biotin status indicator that is not dependent on renal function may be useful in studies of biotin status during pregnancy. A previous study of experimental biotin deficiency suggested that propionyl-coenzyme A carboxylase (PCC) activity in peripheral blood lymphocytes (PBLs) is a sensitive indicator of biotin status. Objective: We examined the utility of measuring PCC activity and the activation of PCC by biotin in detecting marginal biotin deficiency. Design: Marginal biotin deficiency was induced in 7 adults (3 women) by egg-white feeding for 28 d. Blood and urine were obtained on days 0, 14, and 28 (depletion phase) and 44 and 65 (repletion phase). PBLs were incubated with (activated) or without (control) biotin before PCC assay. The activation coefficient of PCC is the ratio of PCC activity in activated PBLs to that in control PBLs. The significance of differences for all measurements was tested by repeated-measures analysis of variance with Fisher's post hoc test and Bonferroni correction. Results: Changes in the urinary excretion of biotin and of 3-hydroxyisovaleric acid confirmed that marginal biotin deficiency was successfully induced. By day 14, PCC activity had decreased (P 0.0001) to below the lower limit of normal in all subjects. By day 28, the activation coefficient of PCC had increased significantly (P ҃ 0.003) and was above the upper limit of normal in 6 of 7 subjects. Conclusion: PCC activity is the most sensitive indicator of biotin status tested to date. In future pregnancy studies, the use of lymphocyte PCC activity data should prove valuable in the assessment of biotin status.Am J Clin Nutr 2006;84:384 -8.