Effects of carbamazepine on self-administration of intravenously delivered cocaine in rats

An Effective Phytoconstituent Aconitine: A Realistic Approach for the Treatment of Trigeminal Neuralgia

Trigeminal neuralgia pain remains a challenge to treat. Natural compounds may be promising options for relieving pain. This study was aimed at investigating the effects of aconitine in a rat model of trigeminal neuralgia pain. Infraorbital nerve chronic constriction injury was performed in adult Wistar Albino rats. After the neuropathic pain developed, the rats were assigned to one of the treatment groups: carbamazepine 40 or 80 mg/kg; aconitine 0.25, 0.50, or 0.75 mg/kg; or saline injection (control group). Behavioral testing with von Frey filaments and the rotarod test were carried out before the surgical procedure and on the 24th to 29th postoperative days. Following the completion of tests, ipsilateral and contralateral spinal cords were harvested for Western blot analyses to assess NR-1 protein expression. ANOVA followed by Mann-Whitney U test was performed for the statistical analyses. P values of <0.05 were considered significant. Aconitine significantly reduced mechanical sensitivity in a dose-dependent manner. A significant reduction in motor coordination was noted for the higher doses of aconitine which was similar with the 40 and 80 mg/kg doses of carbamazepine. NR-1 expression was reduced in the ipsilateral spinal cord, whereas no significant difference was noted between the groups in the expression of NR-1 in the contralateral spinal cord. Aconitine had a significant pain relieving effect, which was similar to carbamazepine, in a dose-dependent manner. Aconitine may be an alternative pharmacological agent for the control of trigeminal neuralgia pain.

Mood stabilizers in the treatment of substance use disorders

Individuals suffering from drug addiction may also manifest features of bipolar spectrum disorders. Hyperthymic and cyclothymic temperaments may render individuals vulnerable to later development of substance abuse. Bipolar disorders themselves may be altered or precipitated by substance use, most notably by stimulants (amphetamines), alcohol, and cannabinoids. The clinical usefulness of mood stabilizers, particularly antiepileptics, has been established as safe and effective in substance abusers with and without comorbid mood disorders. Most studies on this issue have been of short duration and focused on the resolution of a currently manifest period of illness. Few studies have been conducted on the usefulness of these drugs on the long-term longitudinal course of these diseases, such as frequently encountered recurrent relapses into states of agitation, impulsivity, and/or dissatisfaction. As opposed to the clinical experience with traditional antidepressants and neuroleptics, antiepileptics do not induce counter-polar states (depressed patients abruptly turning manic or hypomanic; nor patients currently hypomanic or manic turning abruptly depressed). Many clinicians consider antiepileptic mood stabilizers to be the preferred category of medications for the treatment of such patients. Valproate appears to be a potentially fruitful medication to study in these dual diagnosis patients due to preliminary evidence demonstrating its anticraving efficacy.

GABA modulation of cocaine self-administration

Recent experiments suggest that GABA compounds produce a clinically relevant modulation of cocaine reinforcement. This review summarizes the results of a number of studies that examined the effect of the GABAB agonist baclofen on cocaine self-administration using a variety of schedules of reinforcement. The results demonstrate that baclofen causes a dramatic reduction in cocaine self-administration which does not appear to be accounted for by a general disruption of behavior. However, the effect is dependent on the unit injection dose of cocaine and on the response requirements of the schedule. These results predict that in a clinical setting any potential therapeutic effect of baclofen will interact with the cost and availability of cocaine.

Conditioned taste aversion is a confound in behavioral studies that report a reduction in the reinforcing effects of drugs

Pharmacologic agents with a potential to attenuate the reinforcing properties of drugs of abuse may have an important role in the treatment of drug addiction. The reduction of drug self-administration and sweet solution intake are two common animal models employed to screen for promising therapeutic agents. When these agents are effective in suppressing the behavior maintained by drugs of abuse, the cause is usually attributed to a neuronal mechanism such as the modification of neurotransmitters that subserve reinforcement. These experiments present data for an alternate interpretation which suggest that some of these agents produce a conditioned taste aversion (CTA) that acts as a confounding variable in the screening of potential therapeutic agents. Both carbamazepine and isradipine were shown to establish a CTA at doses reported to attenuate the reinforcing properties of drugs of abuse. It is concluded that CTA represents a potential experimental confound in studies of pharmacologic agents that appear to attenuate the reinforcing properties of drugs. These results suggest that screening for a CTA is necessary in any paradigm that measures the suppression of consummatory behavior in response to pharmacologic intervention.

Evaluation of ADCI against convulsant and locomotor stimulant effects of cocaine: comparison with the structural analogs dizocilpine and carbamazepine

Both the antiepileptic, carbamazepine, and the N-methyl-D-aspartate receptor antagonist, dizocilpine, have shown preclinical efficacy against behavioral and toxic effects of cocaine. Nonetheless, side effects or toxicity of these compounds either alone or in conjunction with cocaine are problematic. 5-Aminocarbonyl-10,11-dihydro-5h-dibenzo[a,d]cyclohepten-5,1 0-imine (ADCI), a molecular hybrid of these compounds, has been shown to have a broad anticonvulsant profile with a good protective index (behavioral TD50/anticonvulsant ED50). In male Swiss Webster mice, ADCI and dizocilpine produced dose-dependent protection against the convulsant effects of cocaine that were insensitive to carbamazepine. However, in contrast to dizocilpine, ADCI did not produce behavioral impairment on the inverted screen test demonstrating a protective index of greater than 15; the protective index for dizocilpine was 1.2. All three compounds attenuated the locomotor stimulant effects of cocaine without significantly decreasing locomotor activity on their own, although the cocaine antagonism was not always dose dependent. Only dizocilpine increased spontaneous locomotor activity when given alone and augmented the locomotor stimulant effects of cocaine. The results confirm the novel anticonvulsant activity of ADCI and its lack of phencyclidine-like behavioral side effects. The data also suggest a modest blocking action of these compounds against the locomotor stimulatory effects of cocaine.

Pharmacotherapy of cocaine abuse: preclinical development

Preclinical models of behavioral and toxic effects of cocaine are reviewed and their potential for predicting compounds with efficacy and safety in the medical management of cocaine abuse and toxicity is assessed. Many of the existing models appear to be good predictors of the effects of compounds against specific behavioral or toxicological actions of cocaine. However, the utility of the models for prediction of the efficacy of new therapeutic entities must await clinical validation as no accepted or standard pharmacotherapy currently exists. Preclinical data generated by these models with drugs currently under clinical investigation for cocaine abuse treatment as well as with other compounds are reviewed. These compounds include buprenorphine, bromocriptine, desmethylimipramine, carbamazepine, dopaminergic agonists, antagonists and partial agonists, dopamine reuptake inhibitors, sigma ligands, serotonin antagonists, and excitatory amino acid antagonists. Preclinical information on several drug classes appears sufficiently promising to warrant further evaluation. These include dopamine agonists and partial agonists, D1 receptor antagonists, selective sigma ligands, and modulators of the N-methyl-D-aspartate subtype glutamate receptor.

Carbamazepine attenuates cocaine-induced increases in dopamine in the nucleus accumbens: an in vivo dialysis study

Carbamazepine's effects on cocaine-induced increases in dopamine overflow in the nucleus accumbens were studied using in vivo microdialysis in anesthetized rats. Rats were chronically treated with a diet containing carbamazepine or no drug for one week prior to microdialysis procedures. The basal levels of dopamine in the nucleus accumbens did not differ between groups; however, the increases in dopamine following cocaine administration (4 mg/kg i.v.) were significantly reduced by carbamazepine. In addition, basal levels of dihydroxyphenyl acetic acid (DOPAC) were significantly diminished in the carbamazepine group and a trend in the same direction was observed for homovanilic acid (HVA). These results are consistent with reports that carbamazepine might decrease dopamine synthesis. Further studies are required to determine the mechanism of carbamazepine's inhibition of cocaine-induced dopamine overflow and its potential clinical implications.

Pharmacogenetic assessment of the effects of carbamazepine on cocaine-kindled and cocaine-induced seizures

The effects of chronic carbamazepine (CBZ) on the development and expression of cocaine-kindled seizures and seizures produced by an acute injection of cocaine were evaluated in BALB/cByJ, C57Bl/6J and SJL/J mice. The repeated administration of a subconvulsant dose of cocaine initially resulted in the development of an increased sensitivity to the convulsant effects of cocaine in the three strains. Chronic, dietary carbamazepine attenuated this initial sensitization to cocaine-induced seizures. While the continued administration of cocaine resulted in a relatively permanent sensitization to cocaine-induced seizures among SJL mice, tolerance to cocaine-induced seizures ultimately developed among C57 mice and to a lesser degree among BALB mice. Genetic factors were found to mediate the effects of chronic CBZ on the development of sensitization and/or tolerance to the convulsant effects of cocaine. Among BALB mice, chronic CBZ appears to have eliminated the development of tolerance to cocaine-induced seizures and allowed an underlying sensitization to be manifest. Among SJL mice, however, the sensitization observed following repeated cocaine injections was reduced, but not eliminated. Genetic factors were also found to be associated with the effects of CBZ on seizures induced by the acute administration of cocaine. BALB and C57 mice, but not SJL mice, chronically treated with dietary CBZ were less susceptible to a consulvant dose of cocaine than their corresponding dietary controls for at least 72 h after stopping CBZ administration. In addition, there were genotype-specific lethal effects associated with the concurrent administration of CBZ and cocaine.

The use of pharmacogenetic techniques in drug abuse research

Pharmacogenetics, the study of genetic factors underlying individual differences in response to drugs, has proven useful for demonstrating that there are large genetic differences in response to a number of abused drugs. Pharmacogenetics also provides a number of useful tools for studying mechanisms underlying the effects of drugs. This review discusses pharmacogenetic techniques with potential utility for drug abuse research and provides examples of their use in studies of the effects of acute and chronic nicotine, cocaine and opiate administration. The importance of using genetically standardized animal models in behavioral and pharmacological research is also discussed.

Carbamazepine produces nonspecific effects on cocaine self-administration in rats

Anecdotal evidence in humans suggest that carbamazepine suppresses cocaine-induced rush and craving. Such claims are unsupported in controlled trials using a placebo control. In the present study, rats were trained to self-administer i.v. cocaine in daily 2-hr sessions in which every tenth lever press delivered 1 mg/kg cocaine. After responding was stable, they were injected before each session with the vehicle for 2 days followed by carbamazepine for 2 days. At a 7 mg/kg dose, carbamazepine was without effect, whereas 15 mg/kg suppressed responding for cocaine only on the second (day 4) day of carbamazepine treatment. With 4 consecutive days of treatment, carbamazepine (15 mg/kg) reduced cocaine-maintained responding slightly, but significantly. In another group of animals trained to lever-press for food reinforcement, carbamazepine (15 mg/kg) also significantly decreased the rate of responding, suggesting that the suppression of responding was not specific to cocaine-reinforced behavior.