Possible involvement of endogenous opioid system located downstream of α7 nicotinic acetylcholine receptor in mice with physical dependence on nicotine

Effect of Withania somnifera (L.) Dunal aqueous root extract on reinstatement using conditioned place preference and brain GABA and dopamine levels in alcohol dependent animals

ETHNOPHARMACOLOGICAL RELEVANCE

Withania somnifera (L.) Dunal (WS), a known'Rasayana' (rejuvenating agent) as per Ayurveda is prescribed to promote health, to increase longevity and to hasten recovery in disease convalescent stages. WS has demonstrated protective effect on alcohol dependence and withdrawal anxiety in previous experimental studies.

AIM OF THE STUDY

To evaluate effect of WS on conditioned place behavioral paradigm (model of relapse) and on GABA and dopamine levels in critical brain areas in alcohol dependent animals.

METHODOLOGY

Following Animal Ethics Committee permission, the mice (n = 24) were divided into the following study groups for experiment 1: 1 -distilled water (vehicle control), 2 -WS and 3 -Naltrexone. They were conditioned on conditioned place preference (CPP) using alcohol (2 gm/kg)/saline (1 ml) administered intraperitoneally for 8 days. WS and Naltrexone were administered during the period of extinction (6-8 days). Effect of WS (650 mg/kg) on reinstating behaviour of mice (time spent in alcohol paired compartment) primed with alcohol injection was noted. In experiment 2, effect of WS (450 mg/kg/) on GABA and dopamine levels in the midbrain, striatum and cortex (ng/gm) were measured in alcohol dependent rats (n = 24) following the first phase of standardisation assay (n = 36). The rats were made alcohol dependent for 15 days (intermittent access model) and WS was administered concurrently. GABA and dopamine levels were measured on Day 16.

RESULTS

WS group showed decrease in time spent in alcohol paired compartment alike Naltrexone and it differed significantly compared to the distilled water control group (p < 0.05) Alcohol-dependent rats showed significant decrease in GABA and increase in dopamine levels vs distilled water in the midbrain, striatum and cortex. WS and Naltrexone administration showed rise in GABA and fall in dopamine in all the isolated brain parts in the respective groups (p < 0.05 vs alcohol treated group).

CONCLUSION

Withania somnifera protected animals from relapse and showed beneficial effects on the brain neurotransmitters involved in alcohol dependence. The study provides substantial evidence for its potential application in alcohol use disorder.

Interactions between nicotine and drugs of abuse: a review of preclinical findings

Polysubstance abuse is common among substance-use disorder patients, and nicotine is one of the most commonly co-used substances. Epidemiological and clinical laboratory studies suggest that nicotine, when combined with other drugs of abuse, increases intake of one or both substances. This review focuses on the preclinical literature regarding nicotine's interaction with alcohol, stimulants (i.e., cocaine, amphetamines), opioids (i.e., morphine, heroin), and Δ⁹-tetrahydrocannabinol (THC). The current understanding of how these various classes of abused drugs may interact with nicotine on behavioral, physiological, and pharmacological indices that may be important in maintaining co-use of one or both substances in human populations are highlighted. Suggestions as to future areas of research and gaps in knowledge are offered.

Postoperative hyperalgesia does not predict persistent post-sternotomy pain; observational study based on clinical examination

BACKGROUND

Persistent post-sternotomy pain is a common problem, but the risk of developing it varies among patients. We sought to find out whether the risk of persistent post-sternotomy pain could be predicted by measuring the area of acute sensory dysfunction around the sternotomy wound. The secondary aim was to determine risk factors for persistent post-sternotomy pain.

PATIENTS AND METHODS

Hundred patients who were scheduled to undergo elective coronary artery bypass surgery were recruited to the study. Patients were excluded if they had undergone previous cardiac surgery or if they lacked co-operation. Preoperative pain scores were determined and the patients filled in questionnaires about depression, anxiety, and pain. The area of sensory dysfunction around the sternotomy wound was assessed by pin prick on postoperative day 4. The presence of persistent post-sternotomy pain was determined at a follow-up evaluation at 4-6 months after surgery.

RESULTS

The sizes of the area of hyperalgesia or overall sensory dysfunction were not associated with persistent post-sternotomy pain. Independent risk factors for persistent post-sternotomy pain were found to be smoking and high pain score on postoperative day 1. The prevalence of persistent post-sternotomy pain in our study population was 38% analyzed by only the questionnaire and 15% according to the clinical examination.

CONCLUSION

Measuring the area of hyperalgesia in the acute phase does not give any additional information on the risk of developing a persistent post-sternotomy pain. We do thus not recommend measuring the area in this particular group of patients. Evaluation of pain by only a questionnaire risks to overestimate the presence of persistent post-sternotomy pain as compared to clinical examination.

Combination of Levo-Tetrahydropalmatine and Low Dose Naltrexone: A Promising Treatment for Prevention of Cocaine Relapse

Relapse to drug use is often cited as the major obstacle in overcoming a drug addiction. Whereas relapse can occur for a myriad of reasons, it is well established that complex neuroadaptations that occur over the course of addiction are major factors. Cocaine, as a potent dopamine transporter blocker, specifically induces alterations in the dopaminergic as well as other monoaminergic neurotransmissions, which lead to cocaine abuse and dependence. Evidence also suggests that adaptations in the endogenous opioids play important roles in pathophysiology of cocaine addiction. Following this evidence, we investigated a combination medication, levo-tetrahydropalmatine (l-THP) and low dose naltrexone (LDN), targeting primarily dopaminergic and endogenous opioid systems as a cocaine-relapse-prevention treatment. In the present study Wistar rats were used to assess the effects ofl-THP and LDN on cocaine self-administration, drug-seeking behavior during cocaine reinstatement, spontaneous locomotion, and effects on the endogenous opioid system. We determined that the combination ofl-THP and LDN reduces drug-seeking behavior during reinstatement more potently thanl-THP alone. Additionally, the combination ofl-THP and LDN attenuates the sedative locomotor effect induced byl-THP. Furthermore, we revealed that treatment with the combination ofl-THP and LDN has an upregulatory effect on both plasmaβ-endorphin and hypothalamic POMC that was not observed inl-THP-treated groups. These results suggest that the combination ofl-THP and LDN has great potential as an effective and well-tolerated medication for cocaine relapse prevention.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

Lack of GABAB receptors modifies behavioural and biochemical alterations induced by precipitated nicotine withdrawal

The nicotine (NIC) withdrawal syndrome is considered to be a major cause of the high relapse rate among individuals undergoing smoking cessation. The aim of the present study was to evaluate a possible role of GABAB receptors in NIC withdrawal, by comparing GABAB1 knockout mice and their wild-type littermates. We analysed the time course of the global withdrawal score, the anxiety-like effects, monoamine concentrations, the brain-derived neurotrophic factor (BDNF) expression, the corticosterone plasmatic levels and [(3)H]epibatidine binding sites during NIC withdrawal precipitated by mecamylamine, a nicotinic receptor antagonist (MEC). In NIC withdrawn wild-type mice, we observed a global withdrawal score, an anxiety-like effect in the elevated plus maze, a decrease of the striatal dopamine and 3,4-dihydroxyphenylacetic acid concentrations, an increase of corticosterone plasma levels, a reduction of BDNF expression in several brain areas and an increase of [(3)H]epibatidine binding sites in specific brain regions. Interestingly, the effects found in NIC withdrawn wild-type mice were absent in GABAB1 knockout mice, suggesting that GABAB1 subunit of the GABAB receptor is involved in the regulation of the behavioural and biochemical alterations induced by NIC withdrawal in mice. These results reveal an interaction between the GABAB receptors and the neurochemical systems through which NIC exerts its long-term effects.