Diazepam Protects Against the Enhanced Toxicity of Cocaine Adulterated With Atropine

Epilepsy and intellectual disability linked protein Shrm4 interaction with GABABRs shapes inhibitory neurotransmission

Shrm4, a protein expressed only in polarized tissues, is encoded by the KIAA1202 gene, whose mutations have been linked to epilepsy and intellectual disability. However, a physiological role for Shrm4 in the brain is yet to be established. Here, we report that Shrm4 is localized to synapses where it regulates dendritic spine morphology and interacts with the C terminus of GABA_B receptors (GABA_BRs) to control their cell surface expression and intracellular trafficking via a dynein-dependent mechanism. Knockdown of Shrm4 in rat severely impairs GABA_BR activity causing increased anxiety-like behaviour and susceptibility to seizures. Moreover, Shrm4 influences hippocampal excitability by modulating tonic inhibition in dentate gyrus granule cells, in a process involving crosstalk between GABA_BRs and extrasynaptic δ-subunit-containing GABA_ARs. Our data highlights a role for Shrm4 in synaptogenesis and in maintaining GABA_BR-mediated inhibition, perturbation of which may be responsible for the involvement of Shrm4 in cognitive disorders and epilepsy.

Mutations in the gene encoding Shrm4 are associated with epilepsy and intellectual disability. The authors show that Shrm4 interacts with GABA_B receptors and regulates tonic inhibition in the hippocampus, and knockdown of Shrm4 in rats leads to anxiety-like behaviour and seizures.

Effects of pretreatment with etomidate, ketamine, phenytoin, and phenytoin/midazolam on acute, lethal cocaine toxicity

OBJECTIVE

To evaluate the effects of etomidate, ketamine, phenytoin, and phenytoin/midazolam in a mouse model of acute cocaine toxicity.

METHODS

We performed a randomized controlled study consisting of five groups (n = 25 each) of rats that received intraperitoneal injections of normal saline solution, 5 mg/kg ketamine, 7.5 mg/kg etomidate, 40 mg/kg phenytoin, and 40 mg/kg phenytoin and 2 mg/kg midazolam 10 minutes before cocaine hydrochloride (105 mg/kg). Following cocaine administration, a blinded observer watched the animals for 30 minutes to assess seizures (popcorn jumping, tonic-clonic activity, or loss of righting reflex), and lethality for 30 minutes.

RESULTS

The number of animals with seizures was lower in the etomidate (60%), phenytoin (40%), and phenytoin/midazolam (40%) groups (P<0.001). The etomidate (24%) and phenytoin/midazolam (16%) treatments were most effective in preventing lethality (P<0.001). Conversely, compared to the vehicle group (72%), cocaine-induced lethality was higher in the ketamine (84%) and phenytoin (92%) groups. All treatments prolonged the time to seizure, but this effect was most pronounced in the etomidate and phenytoin/midazolam groups, which also had the longest average time to lethality.

DISCUSSION

The present study provides the first experimental evidence supporting the use of etomidate to treat cocaine-induced seizures. Notably, ketamine and phenytoin were ineffective. Our findings suggest that premedication with etomidate, phenytoin, and phenytoin/midazolam reduced seizure activity in an acute cocaine toxicity mouse model.