[The cannabis pandemic: why use this expression? Epidemiology]. / La pandémie cannabique : pourquoi cette expression ? Epidémiologie.

Using the term of pandemic to characterize the current use of cannabis is fully warranted considering the results of recent surveys [Halte au cannabis. Paris: Odile Jacob; 2006]. A pandemic is defined as an epidemic affecting populations in a very wide geographical zone which may involve one or several continents.

[Illicit drugs, medications and traffic accidents]. / Drogues, médicaments et accidentologie.

The European Union (EU) has 25 member-states and 455 million inhabitants. Statistics on traffic accidents in the EU show that more than 45,000 people are killed annually, including 5200 in France. At the same time, nearly two million persons in the EU require medical treatment for traffic-accident-related injuries, including 109,000 in France. In addition, traffic accidents are the major cause of death of those individuals aged 15 to 24 years. One third of the EU inhabitants will be hospitalized during their life due to a traffic accident with a cost over 160 billion euro (2-3% of the Gross Domestic Product). An important contributing factor to crashes is the use of alcohol and/or illicit drugs or medication when driving, as they exert negative effects on cognition and psychomotor functions. For illicit drugs, abuse of cannabis with or without alcohol is a major concern for the EU. In fact, three million Europeans use cannabis daily and 80% of them drive after use. A number of French studies since 1999 have underlined the high prevalence of cannabis found in the blood of injured or killed drivers. From medical or judicial observations, it is clear that cannabis use increases the risk of traffic accidents. Many groups outside Europe have also shown the association between drug abuse and crashes. The number of casualties related to certain medicines, especially benzodiazepines remains at a high level, particularly in the elderly. In many countries the prevalence of medicinal drugs associated with car accidents is higher than with cannabis. Annex III of the European Union Council Directive of July the 29th 1991 in fact states that a driving license should not be issued to or renewed for applicants or drivers who are dependent on psychotropic substances or use them regularly. Recently, France has categorized the medicinal drugs available in the country by using three pictograms: level one yellow, "be careful"; level two orange, "be very careful"; level three red, "don't drive". It is an important campaign that increases awareness among the public and the medical professionals about the potential dangerous effects of medicinal drugs when driving. The EU objective of reducing the number of fatalities to 25,000 by 2010 will require strengthening measures against the use of alcohol, illicit and medicinal drugs by not well-informed drivers. It is not only a really great challenge, but also a significant investment towards improving public health in France as well as in Europe.

[Pharmacology, an innovative factor in therapeutic research]. / La pharmacologie, facteur d'innovation en recherche thérapeutique.

As members of the pharmacology training group set up by the committee of pharmacological science of the French Academy of Pharmacy, we examine the situation of pharmacology in drug discovery. Today, it is obvious that by integrating genome sequencing, cellular and molecular biology, and bioinformatics, pharmacology has become a cross-disciplinary science. Pharmacologists must become knowledgeable in a wide range of domains, using the major points in each to direct them towards the discovery and development of new therapeutic agents. It is also clear that pharmacology remains a major factor in the different steps of drug discovery, from the molecular and cellular stages, to clinical and pharmaceutical developments.

Short therapeutic window for MK-801 in transient focal cerebral ischemia in normotensive rats.

The present study investigates the role of N-methyl-D-aspartate (NMDA) receptors in a model of transient focal cerebral ischemia in normotensive rats. The left middle cerebral artery and both common carotid arteries were occluded for 60 min. Preliminary studies indicated that this gave reproducible infarctions of the cortex and striatum. These infarctions were the result of severe ischemia followed by complete reperfusion after clamp removal, as showed by striatal tissue Po2 monitoring. Microdialysis indicated that glutamate concentration increased immediately after occlusion and returned to the baseline value 40 min after clamp removal. MK-801 (1 mg kg-1 i.v.), an antagonist of the NMDA glutamatergic receptor, reduced the cortical infarct volume by 29% (p < 0.001) and the striatal infarct volume by 14% (p < 0.05) when given just prior to ischemia, but had no neuroprotective activity when given 30 min after the onset of ischemia. This short therapeutic window for MK-801 suggests that NMDA receptors play only a transient role in reversible focal ischemia in rats.

alpha-Phenyl-N-tert-butylnitrone attenuates excitotoxicity in rat striatum by preventing hydroxyl radical accumulation.

Various in vitro experiments have indicated that oxygen-derived free radicals may contribute to excitotoxic neuronal death. In the present study we induced excitotoxicity in rat striatum by perfusing glutamate at a high concentration through a microdialysis probe. We observed an increased formation of hydroxyl radicals (.OH) during the perfusion of the excitotoxin and an extensive striatal lesion 24 h after the insult. The spin trap, alpha-phenyl-N-tert-butylnitrone (PBN), attenuated both hydroxyl radical levels and the volume of the lesion. This result suggests that the neuroprotection may be due to a free radical scavenging mechanism. It also implies that PBN may be used in pathological situations involving excitotoxicity such as stroke, brain trauma, and chronic neurologic diseases.

High cardiac zinc levels in spontaneously hypertensive rats.

OBJECTIVES: Higher cardiac zinc levels have been observed previously in spontaneously hypertensive rats (SHR) compared with Wistar-Kyoto (WKY) rats. However, this difference was established in adult males only and needed to be confirmed on a larger number of animals of both sexes. We also explored the respective roles of genetic and environmental factors in the genesis of this zinc anomaly as well as the causal relations with hypertension. DESIGN: Cardiac zinc levels were determined in adult male and female SHR and WKY rats originating from various colonies and submitted to various experimental conditions (anaesthesia, stress). These determinations were also performed in 3-week prehypertensive SHR and in adult Wistar rats submitted or not to deoxycorticosterone acetate-salt-induced hypertension. METHOD: Zinc levels were measured by flame atomic absorption spectrophotometry. RESULTS: In adults, cardiac zinc content was significantly higher in SHR than in WKY rats irrespective of sex and experimental conditions. In young prehypertensive rats, the difference between SHR and WKY cardiac zinc levels was also very significant. Experimental hypertension induced in Wistar rats did not entail any significant rise in cardiac zinc levels. CONCLUSIONS: These findings indicated that the higher cardiac zinc of SHR is not secondary to blood pressure elevation. High erythrocyte zinc, previously described in SHR, together with the present data suggest the occurrence of a primary genetic defect leading to high intracellular zinc in SHR. The possible role of this zinc anomaly in the development of hypertension and/or cardiac hyperplasia is discussed.

The neuroprotective effect of a nitric oxide inhibitor in a rat model of focal cerebral ischaemia.

Recent data showed that glutamate toxicity in primary cortical cultures is mediated by nitric oxide. In order to investigate the effect of inhibition of NO synthase on focal cerebral ischaemia in rats, we studied the histological consequences of a middle cerebral artery (MCA) occlusion after post-operative treatment with NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase. We found a significant reduction of cortical (-43%) and striatal (-25%) necrotic volumes induced by MCA occlusion, indicating that NO synthesis plays an important role in the neurotoxic cascade leading to neuronal damage after focal cerebral ischaemia in rats.

iNOS contribution to the NMDA-induced excitotoxic lesion in the rat striatum.

1. The aim of this study was to assess whether an excitotoxic insult induced by NMDA may induce an iNOS activity which contributes to the lesion in the rat striatum. 2. For this purpose, rats were perfused with 10 mM NMDA through a microdialysis probe implanted in the left striatum. Microdialysate nitrite content, striatal Ca-independent nitric oxide synthase activity and lesion volume were measured 48 h after NMDA exposure in rats treated with dexamethasone (DXM) (3 mg kg(-1) x 4) or aminoguanidine (AG) (100 mg kg(-1) x 4). 3. A significant increase in microdialysate nitrite content and in the Ca-independent NOS activity was observed 48 h after NMDA infusion. Both these increases were reduced by DXM and AG. The NMDA-induced striatal lesion was also reduced by both treatments. 4. Our results demonstrate that NMDA excitotoxic injury induces a delayed, sustained activation of a Ca-independent NOS activity. This activity is blocked by DXM and AG, strongly suggesting the involvement of iNOS. The fact that AG and DXM reduce the NMDA-elicited lesion suggests that iNOS contributes to the brain damage induced by excitotoxic insult.

Dose- and time-dependence of L-NAME neuroprotection in transient focal cerebral ischaemia in rats.

1. In this study the effect of the dose and administration time of NG-nitro-L-arginine methyl ester (L-NAME), an NO-synthase inhibitor, in a model of transient focal cerebral ischaemia in rats was investigated. 2. Two injections of L-NAME were given, of 1, 3 and 10 mg kg-1, 5 min and 3 h after the onset of ischaemia. None of the doses gave any striatal neuroprotection, but 1 and 3 mg kg-1 L-NAME reduced the infarcted volume in the cortex (by 26%, P < 0.01 for 1 mg kg-1 and 21%, P < 0.05 for 3 mg kg-1), whereas 10 mg kg-1 had no neuroprotective effect. 3. Single injections of L-NAME 1 mg kg-1, given 5 min or 3 h after ischaemia onset, had similar neutoprotective effects on the cortical infarction as did the repeated injections. 4. L-NAME 1 mg kg-1 given 3, 6 or 9 h after ischaemia induction reduced the cortical infarct volume by 19% (P < 0.01) when given 3 h after ischaemia, by 21% (P < 0.01) when given at 6 h, and by 16% (P < 0.05) when given at 9 h, but had no neuroprotective activity when given 12 h after ischaemia. 5. Thus a low dose of L-NAME is neuroprotective in a model of transient focal ischaemia, with a wide therapeutic window, much larger than that found or MK-801.

Loss of NADPH-diaphorase containing neurones after reversible focal ischaemia in rats delayed by L-NAME.

In the present study, NADPH-diaphorase histochemistry was used to assess the temporal evolution of the number of nitric oxide (NO)-synthase containing neurones after reversible focal cerebral ischaemia in rats. The number of NADPH-diaphorase containing neurones was reduced by 50% and 90% respectively 6 and 24 h after ischaemia. L-NAME, a NO-synthase inhibitor, prevented the loss of NADPH-diaphorase containing neurones observed 6 h after ischemia but not 24 h after ischaemia, suggesting that in the early phase, nitric oxide is involved in this phenomenon.

Calcium-independent NO-synthase activity and nitrites/nitrates production in transient focal cerebral ischaemia in mice.

1. The temporal changes in constitutive NO-synthase (cNOS) and in calcium-independent NO-synthase activities were studied in mice subjected to 2 h of transient focal cerebral ischaemia. The changes in brain nitrites/nitrates (NOx) content were also studied. 2. NOS activities were measured by the conversion of L-[14C]-arginine to L-[14C]-citrulline. Brain NOx contents were investigated by the Griess colourimetric method. 3. cNOS activity in the infarcted cortical area was significantly reduced after 6 h of reperfusion and this activity remained attenuated for up to 10 days after ischaemia. A calcium-independent NOS activity began to increase 48 h after reperfusion, reached a maximum at 7 days and returned to baseline at 10 days. 4. There was a significant increase of brain NOx content beginning after 3 days of reperfusion. This increase was maximal at 7 days and returned to baseline at 10 days. 5. Thus, ischaemia followed by recirculation leads to a rapid, prolonged drop in cNOS activity in the infarcted cortex. There is also a substantial appearance of calcium-independent NOS activity in the later phase of transient ischaemia, leading to an important increase of NOx production.

Reduction of the neurological deficit in mice with traumatic brain injury by nitric oxide synthase inhibitors.

This study investigates the effect of the NO synthase inhibitors, NG-nitro-L-arginine methyl ester (L-NAME) and 7-nitroindazole (7-NI), on the neurological deficit 24 h after a moderate closed head injury in mice. Low doses of L-NAME or 7-NI given soon after the injury significantly reduced the neurological deficit compared to the vehicle-treated group. L-Arginine (300 mg/kg) did not alter the neurological deficit, but reversed the protective effects of both L-NAME and 7-NI when given at the same time. Both L-NAME and 7-NI had dose-related effects. The neuroprotective effects of L-NAME and 7-NI occurred when the drugs were given 5, 30, or 60 min after brain injury, but not when treatment was begun 2 h after brain injury, suggesting a short therapeutic window for both drugs. These results suggest that NO synthesis by neuronal NO synthase plays an important role in the early neurotoxic cascade leading to neurological deficit following traumatic brain injury.

Reduction of the neurological deficit in mice with traumatic brain injury by nitric oxide synthase inhibitors.

This study investigates the effect of the NO synthase inhibitors, NG-nitro L-arginine methyl ester (L-NAME) and 7-nitro indazole (7-NI), on the neurological deficit 24 h after a moderate closed head injury in mice. Low doses of L-NAME or 7-NI given soon after the injury significantly reduced the neurological deficit compared to the vehicle-treated group. L-Arginine (300 mg/kg) did not alter the neurological deficit, but reversed the protective effects of both L-NAME and 7-NI when given at the same time. Both L-NAME and 7-NI had dose-related effects. The neuroprotective effects of L-NAME and 7-NI occurred when the drugs were given 5, 30, or 60 min after brain injury, but not when treatment was begun 2 h after brain injury, suggesting a short therapeutic window for both drugs. These results suggest that NO synthesis by neuronal NO synthase plays an important role in the early neurotoxic cascade leading to neurological deficit following traumatic brain injury.

Striatal dopamine participates in glutamate-induced hydroxyl radical generation.

Using a microdialysis technique we showed that the exposure of the rat striatum to glutamate yields hydroxyl radicals and results in striatal damage. We postulated that dopamine release is enhanced by glutamate perfusion and that the enzymatic metabolism of dopamine may account for this hydroxyl radical formation. The inhibition of monoamine oxidases by i.p. co-administration of clorgy-line and deprenyl reduced hydroxyl radical production induced by glutamate perfusion, but significantly increased the striatal damage. Our results suggest that the enzymatic metabolism of dopamine participates in glutamate-induced hydroxyl radical generation but that other by-products of dopamine may be responsible for the aggravation of the striatal injury.

Nitric oxide: an endogenous anticonvulsant substance.

In the present study, we examine the involvement of the L-arginine-nitric oxide pathway in seizure activity termination. Convulsions were induced reproducibly by intracerebroventricular administration of N-methyl-D-aspartate to conscious mice. The duration of the seizure activity was increased by inhibition of the NO-pathway or by intracerebroventricular injection of methylene blue, an inhibitor of guanylate cyclase activity. This increased duration in seizure activity was reversed by co-administration of L-arginine or by intracerebroventricular injection of guanosine 3':5' cyclic monophosphate (cGMP). These results suggest that nitric oxide produced in response to NMDA receptor activation leads to an increase in cGMP which induces the seizure activity termination.

Involvement of dopaminergic receptors in quinolinate-induced striatal lesions.

The purpose of this study was to examine the effects of blockade (sulpiride) and activation (quinpirole) of dopaminergic D2 (DA2) receptors on brain lesions subsequent to excessive activation of glutamate (GLU) receptors. Striatal lesions were produced by direct injection of quinolinic acid, an endogenous GLU receptor agonist. Sulpiride (100 mg kg-1 i.p., 30 min before quinolinic acid injection and 1 h after) significantly (p < or = 0.05) reduced the volume of the lesion by around 20%. Quinpirole (1.25 mg kg-1 i.p., 30 min before quinolinic acid injection) had no effect. The protective action of DA2 receptor blockade strongly suggests that quinolinic acid-induced excitotoxicity may be partly modulated by DA2 receptors.

Effect of kynurenic acid on the ischaemia-induced accumulation of glutamate in rat striatum.

We examined the effect of kynurenic acid, a broad spectrum antagonist of excitatory amino acid receptors, on striatal extracellular glutamate and aspartate accumulation induced by a 30 min forebrain ischaemia in rats. Kynurenic acid, given systemically (500 mg kg-1, i.p.) or administered in situ through the dialysis probe (10 mM), markedly depressed the ischaemia-induced increase in glutamate and aspartate concentrations. These results indicate that, during forebrain ischaemia, local glutamate receptors play a major role in glutamate and aspartate accumulation in the striatum. Ischaemia-induced increase in extracellular concentrations of these excitatory amino acids may be due in part to a positive glutamatergic feedback loop via activation of NMDA and/or non-NMDA receptors.

Competitive NMDA receptor blockers reduce striatal glutamate accumulation in ischaemia.

Our previous studies have shown that kynurenic acid, a broad-spectrum antagonist of excitatory amino acid receptors, depressed the ischaemia-induced accumulation of glutamate and aspartate in rat striatum. In the present experiments we examined the effect of two competitive N-methyl-D-aspartate (NMDA) receptor antagonists on striatal extracellular glutamate concentrations induced by a 30 min '4-vessel occlusion' ischaemia in rats. Local perfusion with 2-amino-5-phosphonovalerate (AP5; 300 microM) and with 2-amino-7-phosphonoheptanoate (AP7; 300 microM), using a microdialysis fibre markedly reduced the ischaemia-induced increase in glutamate concentrations. These results indicate that, during forebrain ischaemia the NMDA receptor type mediates glutamate and aspartate accumulation in rat striatum.

Deleterious Ca-independent NOS activity after oxidative stress in rat striatum.

The aim of this study was to assess whether oxidative stress induces deleterious NOS activity in the central nervous system (CNS). For this purpose, the mitochondrial toxin malonate, which promotes free radical production, was infused into the left striatum of rats. Forty-eight hours after injection, an increase in Ca-independent NOS activity was observed in the injected striatum. This increase was blocked by alpha-phenyl-tert-butyl-nitrone, a free radical scavenger, and by aminoguanidine, an inhibitor of NOS 2. Both these drugs reduced the malonate-induced striatal necrotic volume. These results suggest that in the CNS oxidative stress can induce a Ca-independent NOS, probably of type 2, which contributes to the lesion.

Enhancement of endogenous excitatory amino acids by theophylline does not modify the behavioral and histological consequences of forebrain ischemia.

The neuroprotective role of endogenous adenosine during forebrain ischemia elicited by 4-vessel occlusion in rats was assessed using the adenosine antagonist, theophylline (32 mg/kg). Despite an increase in the release of glutamate in the hippocampus during ischemia, theophylline did not alter the neurological and histological outcomes. These results indicate that endogenous adenosine does not act as an endogenous neuroprotector by modulating glutamate release in this model.