Expression of mutant beta2 nicotinic receptors during development is crucial for epileptogenesis.

Autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE) is a focal form of epilepsy characterized by seizures occurring during non-REM sleep. We have developed and characterized the first mouse model for ADNFLE type III carrying the V287L mutation of the beta2 subunit of neuronal nicotinic receptor. Mice expressing mutant receptors show a spontaneous epileptic phenotype by electroencephalography with very frequent interictal spikes and seizures. Expression of the mutant beta2 subunit is driven by a neuronal-specific tetracycline-controlled promoter, which allows planned silencing of transgene expression in a reversible fashion and tracking the involvement of mutant receptor in crucial phases of epileptogenesis. We found that restricted silencing during development is sufficient to prevent the occurrence of epileptic seizures in adulthood. Our data indicate that mutant nicotinic receptors are responsible for abnormal formation of neuronal circuits and/or long-lasting alteration of network assembly in the developing brain, thus leading to epilepsy.

Diazepam protects against the enhanced toxicity of cocaine adulterated with atropine.

We examined the toxicity of cocatropine (cocaine/atropine mixture) and the therapeutic potential of diazepam on some behavioral and physiological parameters in rats. Atropine (20 and 60 mg/kg) or cocaine (40 mg/kg) alone did not induce any seizure or death, but the combination significantly increased both, after both acute and binge treatment. There was a significant increase of EEG mean total spectral power in cocatropine- in comparison with cocaine-treated animals. Hyperlocomotion was observed in non-seizuring rats treated with cocaine or cocatropine. Cocaine, atropine 60, and cocatropine (40 + 20 and 40 + 60) all induced hyperthermic effects in non-seizuring rats, while cocatropine (40 + 60)-seizuring animals had hypothermia. An initial hypertensive and tachycardiac effect within 15 min was followed by a secondary fall in the cocatropine (40 + 60) group. Cocatropine toxicity was partially or fully reversed by diazepam (5 mg/kg), given intraperitoneally after the first seizure. The present findings provide, for the first time, details of a synergistic toxic effect of the cocaine/atropine mixture and of the potential of diazepam for treating cocatropine-related hospital emergencies.

Hallucinatory and rewarding effect of salvinorin A in zebrafish: kappa-opioid and CB1-cannabinoid receptor involvement.

RATIONALE: The hallucinatory effect and potential abuse of salvinorin A, the major ingredient of Salvia divinorum, has not been documented in animals. OBJECTIVE: The effects of salvinorin A on the zebrafish (Danio rerio) model, through its swimming behavior and conditioned place preference (CPP) task, was studied. MATERIALS AND METHODS: Swimming activity was determined in a squared observational chamber after an i.m. treatment of salvinorin A (0.1-10 microg/kg). For the CPP test, zebrafish were given salvinorin A (0.2 and 1 microg/kg) or vehicle and evaluated in a two-compartment chamber. RESULTS: Salvinorin A (0.1 and 0.2 microg/kg) induced accelerated swimming behavior in comparison with vehicle, whereas a "trance-like" effect, at doses as 5 and 10 microg/kg, was obtained. Pretreatment with the kappa-opioid antagonist, nor-binaltorphimine (nor-BNI; 10 mg/kg) and the cannabinoid type 1 (CB(1)) antagonist, rimonabant (1 mg/kg), blocked salvinorin A-induced both stimulating and depressive effects obtained at a dose of 0.2 and 10 microg/kg, respectively. In the CPP test, salvinorin A (0.2 and 0.5 microg/kg) produced an increase in the time spent in the drug-associated compartment. A dose of 1 microg/kg produced no effect, whereas a dose of 80 microg/kg induced aversion. Pretreatment with nor-BNI or rimonabant fully reversed the reinforcing properties of salvinorin A (0.5 microg/kg). CONCLUSIONS: Taken together, these results indicate that salvinorin A, as is sometimes reported in humans, exhibits rewarding effects, independently from its motor activity, suggesting the usefulness of the zebrafish model to study addictive behavior. These effects appear mediated by activation of both kappa-opioid and cannabinoid CB(1) receptors.

Vanilloid VR1 receptor is involved in rimonabant-induced neuroprotection.

Recently, a potential neuroprotective effect of rimonabant, independent of the CB1 receptor interaction, has been proposed. In the present study, the role of transient receptor potential channel vanilloid subfamily member 1, named VR1, on neuroprotective effect of rimonabant, on global cerebral ischemia in gerbils, was investigated. Rimonabant (0.05-3 mg kg-1), given i.p. 5 min after recirculation, dose dependently antagonized the ischemia-induced decrease in electroencephalographic (EEG) total spectral power and restored relative frequency band distribution 7 days after ischemia. Rimonabant (0.125-0.5 mg kg-1) fully prevented ischemia-induced hyperlocomotion 1 day after ischemia and memory impairment evaluated in a passive avoidance task, 3 days after ischemia. At 7 days after ischemia, the survival of pyramidal cells, in the CA1 subfield, was respectively 91 and 96%, in the animals given rimonabant 0.25 and 0.5 mg kg-1, compared to the vehicle group. Higher doses were not protective. The protection induced by rimonabant followed a bell-shaped curve, the maximal active doses being 0.25 and 0.5 mg kg-1. Capsazepine (0.01 mg kg-1), a selective VR1 vanilloid receptor antagonist, completely reversed rimonabant-induced neuroprotective effects against EEG flattening, memory impairment and CA1 hippocampal neuronal loss. These findings suggest that VR1 vanilloid receptors are involved in rimonabant's neuroprotection even if other mechanisms can contribute to this effect.

Capsaicin exhibits neuroprotective effects in a model of transient global cerebral ischemia in Mongolian gerbils.

1. Capsaicin, the irritant principle of hot peppers, is a vanilloid agonist known to activate the transient receptor potential channel vanilloid subfamily member 1 (VR1), recently reported to be involved in neurodegeneration. The present study investigated the role of VR1 in a model of global cerebral ischemia in gerbils. 2. Over the dose range tested, capsaicin (0.01, 0.025, 0.05, 0.2 and 0.6 mg kg(-1)), given 5 min after recirculation, dose-dependently antagonized the ischemia-induced electroencephalographic total spectral power decrease and restored relative frequency band distribution evaluated 7 days after ischemia. 3. Capsaicin, at all tested doses, fully prevented ischemia-induced hyperlocomotion evaluated 1 day after ischemia. 4. Capsaicin dose-dependently antagonized ischemia-induced memory impairment evaluated in a passive avoidance task, 3 days after ischemia. 5. Capsaicin showed a dose-dependent hypothermic effect evaluated for 2 h after recirculation. 6. At 7 days after ischemia, a progressive survival of pyramidal cells in the CA1 subfield in capsaicin-treated gerbils, with a maximum of 80%, at a dose of 0.2 mg kg(-1), was obtained. 7. The selective VR1 antagonist, capsazepine (0.01 mg kg(-1)), reversed capsaicin-induced protective effects, in a competitive manner. 8. These results suggest that the neuroprotective effect of capsaicin may be attributable, at least in part, to VR1 desensitization and provide a valuable target for development of interventional pharmacological strategies.

Delta9-tetrahydrocannabinol-induced conditioned place preference and intracerebroventricular self-administration in rats.

On the basis of contradictory findings on the rewarding effects of Delta9-tetrahydrocannabinol (Delta9-THC) in laboratory animals, the effect of the compound on conditioned place preference and intracerebroventricular (i.c.v.) self-administration in a free-choice procedure, using a wide range of doses (0.015-6 mg/kg for conditioned place preference test and 0.01-1 microg/2 microl/infusion for i.c.v. self-administration), was studied in Wistar rats. The present results showed that Delta9-THC induced reward in both tests, but only at the lowest tested doses (0.075-0.75 mg/kg i.p. for conditioned place preference test and 0.01-0.02 microg/infusion for i.c.v. self-administration). This effect was fully antagonised by i.p. pretreatment with the cannabinoid CB1 receptor antagonist, SR 141716A [N-piperidino-5-(4-chlorophenyl)1-(2,4-dichlorophenyl)-4 methyl pyrazole 3-carboxamide] (0.25-1 mg/kg), and the opiate receptor antagonist, naloxone (0.5-2 mg/kg), suggesting the involvement of both endocannabinoid and opioid systems. In conclusion, these findings demonstrate, for the first time, that low doses of Delta9-THC can act as an effective reinforcer in Wistar rats providing a reliable animal model of human marijuana abuse.

Post-ischemic treatment with cannabidiol prevents electroencephalographic flattening, hyperlocomotion and neuronal injury in gerbils.

The potential activity of cannabidiol, a non-psychoactive constituent of marijuana, in preventing damage caused by cerebral ischemia was studied. Cannabidiol (1.25-20 mg/kg) was given 5 min after 10 min bilateral carotid occlusion in freely-moving awake gerbils. Seven days after ischemia, it antagonized the electroencephalographic flattening of total spectral power, with a dose-dependent bell-shaped curve; the neuroprotective effect was greatest with 5 mg/kg. One day after ischemia cannabidiol completely antagonized ischemia-induced hyperlocomotion, at all doses. Rectal temperature did not change during the first hour after occlusion. Histological examination showed complete survival of CA1 neurons in cannabidiol-treated gerbils. These findings suggest a potential therapeutic role of cannabidiol in cerebral ischemia, though the clear mechanism of action remains to be elucidated.