The role of calcium channels in drug dependence

Genetics Influences Drug Consumption in Medication Overuse Headache, Not in Migraine: Evidence From Wolframin His611Arg Polymorphism Analysis

Background: The Wolframin His611Arg polymorphism can influence drug consumption in psychiatric patients with impulsive addictive behavior. This cross-sectional study aims to assess the prevalence of the Wolframin His611Arg polymorphism in MOH, a secondary headache belonging to the spectrum of addictive disorders, episodic migraine (EM), and healthy subjects (HS), and its influence on drug consumption.

Methods: One-hundred and seventy-two EM, 107 MOH, and 83 HS were enrolled and genotyped for the Wolframin His611Arg polymorphism. Subjects were classified as homozygous for allele His (H/H subjects), homozygous for allele Arg (R/R subjects), and heterozygous (H/R subjects), regrouped as R/R and carriers of allele H (non-R/R), and matched for clinical data.

Results: There were no differences in allelic distributions between the three groups (p = 0.19). Drug consumption and other clinical characteristics were not influenced by the Wolframin His611Arg polymorphism (p = 0.42; β = 0.04) in the EM group. Among the MOH population, R/R subjects consumed more analgesics (p < 0.0001; β = −0.38), particularly combination drugs (p = 0.0001; d = 2.32).

Discussion: The Wolframin His611Arg polymorphism has a similar prevalence between the MOH, EM, and HS groups. The presence of the R/R genotype does not influence symptomatic drug consumption in EM, whereas it determines an increased use of symptomatic drugs in the MOH group, in particular combination drugs (i.e., drugs containing psychoactive compounds).

Conclusions: Our findings are consistent with the hypothesis that the Wolframin His611Arg polymorphism plays its effect only in the MOH population, influencing the impulsivity control underlying addictive behavior.

Alleviation of Morphine Withdrawal Signs but Not Tolerance by the Essential Oil of Kelussia odoratissima Mozaff

The aim of the present study was to assess the effects of chronic and acute treatment of the essential oil (EO) of Kelussia odoratissima Mozaff. on the development of morphine tolerance and dependence in mice. Mice were rendered tolerant to and dependent on morphine by subcutaneous injection of morphine over a period of 5 days. Tolerance was assessed using the tail-pinch test and withdrawal signs of morphine were precipitated by injecting naloxone 2 h after the final morphine injection. Repeated injection of the EO of K. odoratissima (5 and 10 mg/kg) for 4 days significantly suppressed morphine-withdrawal jumps, a sign of the development of dependence to opiate as assessed by naloxone precipitation withdrawal on day 5 of testing. A single injection (25, 50, 100 mg/kg) of the EO on day 5, 1 h prior to morphine failed to produce any significant change in morphine withdrawal signs. Neither the acute nor the chronic administration of EO of the K. odoratissima did significantly influence the development of tolerance to the analgesic effect of morphine. Alleviation in morphine signs of withdrawal after chronic injection with K. odoratissima is indicative of reversal of neuronal adaptation that takes place during morphine presence in the brain.

Role of calcium in morphine dependence and naloxone-precipitated withdrawal in mice

PURPOSE

To explore the role of calcium in morphine withdrawal syndrome using various agents affecting calcium levels in cytoplasm.

METHODS

Mice were rendered dependent on morphine by subcutaneous injection of morphine, and withdrawal was induced 4 hours later by injecting the opioid antagonist, naloxone. Mice were observed for 30 minutes for signs of withdrawal, ie, characteristic jumping, hyperactivity, urination, and diarrhea. Various calcium channel blockers were injected intraperitoneally 30 minutes before naloxone to evaluate their influence on the severity of the withdrawal syndrome. We also tested the effect of combination levodopa-carbidopa pretreatment and its interaction with a selective alpha-1 blocker, terazosin, on naloxone-precipitated withdrawal in mice acutely dependent on morphine.

RESULTS

A significant dose-dependent attenuation of naloxone-induced morphine withdrawal syndrome was observed with calcium channel blockers, ie, verapamil 20 mg/kg (P < 0.05) and diltiazem 30 mg/kg (P < 0.01). Combination levodopa-carbidopa pretreatment facilitated the morphine withdrawal syndrome, and this was found to be blocked by terazosin, although not to a statistically significant (P > 0.05) extent.

CONCLUSION

The results indicate that calcium plays an important role in the genesis of morphine dependence and withdrawal, and suggest the usefulness of calcium channel blockers in the management of morphine withdrawal syndrome.

Calcium channel antagonists suppress cross-tolerance to the anxiogenic effects of D-amphetamine and nicotine in the mouse elevated plus maze test

The purpose of the current experiments was to examine the anxiety-related effects of repeated amphetamine and nicotine administration using the mouse elevated plus maze (EPM). d-amphetamine was administered daily for 8 days (2 mg/kg, i.p.). On the 9th day, mice were challenged with amphetamine (2 mg/kg, i.p.) or nicotine (0.1 mg/kg, s.c.), and were tested 30 min after this last injection. Additionally, a distinct group of mice was pretreated with nicotine (0.1 mg/kg, s.c., 6 days). These mice were subjected to nicotine (0.1 mg/kg, s.c.) or amphetamine (2 mg/kg, i.p.) challenge on the seventh day to see if full crossover effects developed after the pretreatment of both psychostimulant drugs. Moreover, the L-type voltage-dependent calcium channel antagonists nimodipine (5 and 10 mg/kg, i.p.), flunarizine (5 and 10 mg/kg, i.p.), verapamil (5 and 10 mg/kg, i.p.) and diltiazem (5 and 10 mg/kg, i.p.) were injected prior to each injection of chronic d-amphetamine or nicotine. We observed cross-tolerance to the anxiogenic effects of d-amphetamine and nicotine that was blunted by a pretreatment with calcium channel blockers. Overall our findings imply that similar neural calcium-dependent mechanisms are involved in the anxiety-related responses to chronic amphetamine and nicotine injections. As anxiety seems to be an important factor for the development of psychostimulant dependence, the L-type VDCC antagonists can offer an interesting approach for the pharmacotherapy of addiction, including amphetamine and/or nicotine dependence.

The wolframin His611Arg polymorphism influences medication overuse headache

Homozygosis for wolframin (WFS1) mutations determines Wolfram syndrome (WS), and common polymorphisms of WFS1 are associated with psychiatric illnesses and dependence behaviour. To test the influence of WFS1 polymorphisms on medication overuse headache (MOH), a chronic headache condition related to symptomatic drugs overuse, we analyzed 82 MOH patients for the WFS1 His611Arg polymorphism, and performed a comparison between clinical features of Arg/Arg (R/R) and non-R/R individuals. Individuals harbouring the R/R genotype showed significantly higher monthly drug consumption (t=-3.504; p=0.00075) and more severe depressive symptoms on the BDI questionnaire (t=-3.048; p=0.003) than non-R/R. WFS1 polymorphism emerged as the only significant predictor of drug consumption, at the multivariate regression analysis (F=12.277; d.f.=1,80; p=0.00075, adjusted R2=0.122). These results implicate WFS1 in the clinical picture of MOH, may be through an influence on need for drugs as in other conditions of abuse behaviour.

Effects of acute and chronic nicotine on elevated plus maze in mice: Involvement of calcium channels

The current experiments examined the anxiety-related effects of acute and repeated nicotine administration using the elevated plus maze test in mice. Nicotine (0.1 mg/kg s.c., 5 and 30 min after injection; 0.5 mg/kg, s.c., 5 min after injection) had an anxiogenic effect, shown by specific decreases in the percentage of time spent on the open arms and in the percentage of open arm entries. Tolerance developed to this anxiogenic action after 6 days of daily nicotine administration (0.1 mg/kg, s.c.). Five minutes after the seventh injection, an anxiolytic effect was observed, i.e., specific increases in the percentage of time spent on the open arms and in the percentage of open arm entries. L-type voltage-dependent calcium channel antagonists nimodipine (5 and 10 mg/kg, i.p.), flunarizine (5 and 10 mg/kg, i.p.), verapamil (5, 10, 20 mg/kg) and diltiazem (5, 10, 20 mg/kg, i.p.) were also injected prior to an acute low dose of nicotine or to each injection of chronic nicotine. Our results revealed that calcium channel blockers dose-dependently attenuated both an anxiogenic effect of nicotine as well as the development of tolerance to this effect. Our results suggest that neural calcium-dependent mechanisms are involved in the anxiety-related responses to acute and chronic nicotine injection that may ultimately lead to addiction and smoking relapse in human smokers.

Blockade of the expression of mecamylamine-precipitated nicotine withdrawal by calcium channel antagonists

The present study focused on the evaluation of nicotine abstinence syndrome in mice and on the influence of calcium channel blockers on the expression of the somatic signs of nicotine withdrawal. Our experimental protocol consisted of intermittent administration of nicotine, 2.5 mgkg(-1), subcutaneously (s.c.), four times daily for 7 days. In attempt to precipitate nicotine abstinence, mice were given one injection of mecamylamine (3 mgkg(-1), intraperitoneally (i.p.)), 1h after the last nicotine injection, on the test day (day 8) in the morning. Additionally, body weight changes, locomotor activity and anxiogenic responses in the elevated plus maze test were also evaluated in nicotine withdrawn mice. Our data shown that the L-type calcium channel antagonists, nimodipine, verapamil, flunarizine and diltiazem (5 and 10 mgkg(-1), i.p., each), injected before mecamylamine administration, dose-dependently attenuated the expression of nicotine withdrawal signs. Moreover, 24h after terminating nicotine treatment, we also observed additional nicotine abstinence measures, such as loss of body weight followed by a slight body weight gain, decrease of spontaneous locomotor activity and anxiogenic responses. These findings obtained using our valuable rodent model of nicotine dependence suggest the involvement of calcium-dependent mechanisms in the expression of mecamylamine-precipitated nicotine abstinence syndrome.

Deletion of N-type calcium channels alters ethanol reward and reduces ethanol consumption in mice

N-type calcium channels are modulated by acute and chronic ethanol exposure in vitro at concentrations known to affect humans, but it is not known whether N-type channels are important for behavioral responses to ethanol in vivo. Here, we show that in mice lacking functional N-type calcium channels, voluntary ethanol consumption is reduced and place preference is developed only at a low dose of ethanol. The hypnotic effects of ethanol are also substantially diminished, whereas ethanol-induced ataxia is mildly increased. These results demonstrate that N-type calcium channels modulate acute responses to ethanol and are important mediators of ethanol reward and preference.

Nimodipine in opiate detoxification: a controlled trial

OBJECTIVE

To evaluate the use of L-type calcium channel blockers (CaCB) in out-patient opiate detoxification.

DESIGN

Controlled trial with sequential allocation of patients to groups.

METHODS

Three groups of individuals subject to opiate detoxification were involved: (1) the experimental group (n=30) received a course of nimodipine and dextropropoxiphen; (2) one control group (n=20) was detoxified with a course of dextropropoxiphen and benzodiazepine; and (3) a second control group (n=30) was treated with a standard course of alpha-2-adrenergic agents and naltrexone. In all cases, the detoxification course was scheduled to last 7 days.

RESULTS

All the groups showed a significant opiate withdrawal syndrome (OWS) during detoxification (follow-up effect: Lambda=0.04; F6.52=201.89; P < 0.001), but from the first day the group treated with CaCB manifested fewer symptoms than the control groups (treatment effect: F2.57=97.99; P < 0.001). From the start, the intensity of the OWS was reduced by half in the CaCB group (M=6.67) compared with that manifested by the two other groups (M approximately 13). The clinical impression of the evolution of the detoxification was that it was comfortable and free of complications (significant side-effects were not observed).

CONCLUSIONS

The results of the study suggest that the use of calcium channel blockers (CaCB) may be an effective method in opiate detoxification. Full randomized trials are warranted.

Effects of calcium channel blockers on behaviors induced by the N-methyl-D-aspartate receptor antagonist, dizocilpine, in rats

The present study assessed the ability of voltage-sensitive calcium channel (VSCC) blockers to affect the behavioral effects of the noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist, dizocilpine, in male Wistar rats. Dizocilpine produced dose-dependent increases in locomotor activity. Nimodipine, verapamil, and flunarizine suppressed dizocilpine-facilitated vertical activity, while horizontal activity was attenuated by verapamil and nimodipine but not flunarizine. Repeated dizocilpine injections resulted in the development of sensitization to its locomotor stimulating properties. Development of sensitization was not context specific, and was observed following repeated exposures to 0.1 but not 0.056 or 0.3 mg/kg of dizocilpine. Nimodipine retarded the development of sensitization to dizocilpine's stimulating effects on horizontal activity, while verapamil suppressed sensitization to the vertical stimulating effects of dizocilpine. Flunarizine had no significant effects on sensitization to dizocilpine's locomotor stimulating properties. In rats trained to discriminate between injections of 0.056 mg/kg of dizocilpine and vehicle, none of the tested VSCC blockers was able to completely antagonize the discriminative stimulus properties of dizocilpine. Nimodipine, when administered in combination with the training dose of dizocilpine, modestly decreased the dizocilpine-lever selection. Dizocilpine dose dependently decreased the self-determined stimulation threshold implanted in rats with electrodes into the ventral tegmental area. Nimodipine exhibited some tendency to block the facilitating effects of dizocilpine, while verapamil and flunarizine had no effects. In summary, in the present experiments VSCC blockers exerted only modest interactions with the behavioral effects of dizocilpine, and it is unlikely that VSCC blockers have remarkable potential as adjunct treatment aimed at correcting the negative side effects of NMDA receptor antagonists (e.g., dizocilpine).

The pharmacology of ion channels: with particular reference to voltage-gated Ca2+ channels

Ion channels are molecular machines that serve as principal integrating and regulatory devices for the control of cellular excitability. They are also major targets for drug action. The basic aspects of ion channel structure and pharmacological control are reviewed and illustrated with specific reference to a major class of therapeutic agents and molecular tools--the clinically available Ca2+ channel antagonists.

Differentiation of the inhibitory effects of calcium antagonists on abnormal behaviors induced by methamphetamine or phencyclidine

The abnormal behaviors induced by methamphetamine (MAP: 1 mg/kg) or phencyclidine (PCP: 10 mg/kg) were measured using behavioral analysis following the microinjection of one of three calcium (Ca) antagonists (nifedipine: Nif, nicardipine: Nic and flunarizine: Flu) into the rat caudate putamen or amygdala. The intraperitoneal administration of MAP or PCP induced abnormal behaviors in a time-dependent manner; the maximum locomotor activity was measured 30-45 min after the administration of MAP or PCP. This hyperactivity was sustained for more than 2 h. Following microinjection of these Ca antagonists into the caudate putamen, each showed a different pattern of inhibition on MAP- or PCP-induced abnormal behaviors. Nic and Flu were effective at reducing these abnormal behaviors, in contrast, Nif was ineffective. In particular, the inhibitory effect of Nic was stronger than that of Flu. Microinjection of these Ca antagonists into the amygdala did not show any reductive effect on the hyperactivity induced by MAP or PCP. These results demonstrate that these Ca antagonists have different pharmacological properties and that both L- and T-type Ca2+ channels modulate the dopamine release in the rat caudate putamen. These results further lead us to suggest the presence of a subtype of L-type Ca2+ channels in the caudate putamen.

Insulin-like growth factor I expression alters acute sensitivity and tolerance to ethanol in transgenic mice

We compared some biobehavioral effects of ethanol in transgenic mice that overexpress insulin-like growth factor I (IGF-I) in brain and in those that exhibit ectopic: brain expression of IGF binding protein I with those in non-transgenic littermate controls. Ethanol-induced sleep in IGF-I transgenic mice was significantly shorter, and in IGF binding protein 1 transgenic mice significantly longer, than in controls. A similar tendency, though not significant, was observed for ethanol-induced hypothermia. The groups did not differ in the degree of ethanol-induced ataxia. IGF-I transgenic mice did not acquire tolerance to either the hypothermic or hypnotic effects of ethanol following 7-day ethanol treatment. In contrast, tolerance in IGF binding protein 1 transgenic mice was significantly more pronounced than in controls. There were no significant differences among the three groups in the peak blood alcohol concentrations or the overall blood alcohol curves following acute ethanol challenge. In general, these data support the prediction made that chronically elevated exposure to IGF-I in IGF-I transgenic mice renders them less susceptible to the effects of ethanol than their non-transgenic siblings, and that overexpression of IGF binding protein 1 has the opposite effect.