Rimonabant attenuates amphetamine sensitisation in a CCK2 receptor-dependent manner

CCK2-receptor deficiency impairs immune balance by influencing CD4+ T cells development by inhibiting cortical-thymic-epithelial-cells

Immune balance is crucial for an organism's survival and is inseparable from the regulation of the nervous system. Accumulating evidence indicates that cholecystokinin (CCK) plays an important role in mediating the immune response through the activation of cholecystokinin receptors (CCKRs). However, it remains unclear whether CCKRs deficiency may impair immune balance. Here, we showed that CCK2R-deficient adult mice were immunocompromised and had an increased risk of shock and even death in an endotoxemia (ETM)/endotoxin shock (ES) model. In addition, in both adult and juvenile mice, CCK2R deficiency not only influenced the development of CD4 single-positive (SP) thymocytes in thymic positive selection but also decreased the population of CD3+ CD4+ T cells in the spleen. More importantly, CCK2R deficiency inhibited the expression of major histocompatibility complex class II (MHC II) and CD83 on cortical thymic epithelial cells (cTECs) in juvenile and adult mice. Overall, our study suggests that CCK2R is essential for maintaining CD4+ T cell development in the thymus and reveals that CCK2R plays an important role in maintaining immune balance.

Cholecystokinin-Mediated Neuromodulation of Anxiety and Schizophrenia: A "Dimmer-Switch" Hypothesis

Cholecystokinin (CCK), the most abundant brain neuropeptide, is involved in relevant behavioral functions like memory, cognition, and reward through its interactions with the opioid and dopaminergic systems in the limbic system. CCK excites neurons by binding two receptors, CCK1 and CCK2, expressed at low and high levels in the brain, respectively. Historically, CCK2 receptors have been related to the induction of panic attacks in humans. Disturbances in brain CCK expression also underlie the physiopathology of schizophrenia, which is attributed to the modulation by CCK1 receptors of the dopamine flux in the basal striatum. Despite this evidence, neither CCK2 receptor antagonists ameliorate human anxiety nor CCK agonists have consistently shown neuroleptic effects in clinical trials. A neglected aspect of the function of brain CCK is its neuromodulatory role in mental disorders. Interestingly, CCK is expressed in pivotal inhibitory interneurons that sculpt cortical dynamics and the flux of nerve impulses across corticolimbic areas and the excitatory projections to mesolimbic pathways. At the basal striatum, CCK modulates the excitability of glutamate, the release of inhibitory GABA, and the discharge of dopamine. Here we focus on how CCK may reduce rather than trigger anxiety by regulating its cognitive component. Adequate levels of CCK release in the basal striatum may control the interplay between cognition and reward circuitry, which is critical in schizophrenia. Hence, it is proposed that disturbances in the excitatory/ inhibitory interplay modulated by CCK may contribute to the imbalanced interaction between corticolimbic and mesolimbic neural activity found in anxiety and schizophrenia.

Neuroinflammation as a possible link between cannabinoids and addiction

OBJECTIVE

Substance dependence disorder is a chronically relapsing condition characterised by neurobiological changes leading to loss of control in restricting a substance intake, compulsion and withdrawal syndrome. In the past few years, (endo)cannabinoids have been raised as a possible target in the aetiology of drug addiction. On the other hand, although the exact mechanisms of the genesis of addiction remain poorly understood, it is possible that neuroinflammation might also play a role in the pathophysiology of this condition. Studies demonstrated that (endo)cannabinoids act as immunomodulators by inhibiting cytokines production and microglial cell activation. Thus, in the present review, we explore the possible role of neuroinflammation on the therapeutic effects of cannabinoids on drug addiction.

METHODS

We conducted an evidence-based review of the literature in order to assess the role of cannabinoids on the neuroinflammatory hypothesis of addiction (terms: addiction, cannabinoids and inflammation). We searched PubMed and BioMedCentral databases up to April 2014 with no date restrictions.

RESULTS

In all, 165 eligible articles were included in the present review. Existing evidence suggests that disruption in cannabinoid signalling during the drug addiction process leads to microglial activation and neuroinflammation.

CONCLUSION

The literature showed that inflammation and changes in endocannabinod signalling occur in drug abuse; however, it remains uncertain whether these changes are causally or coincidentally associated with addiction. Additional studies, therefore, are needed to elucidate the contribution of neuroinflammation on the behavioural and neuroprotective effects of cannabinoids on drug addiction.

Effects of exogenous cholecystokinin octapeptide on acquisition of naloxone precipitated withdrawal induced conditioned place aversion in rats

Cholecystokinin octapeptide (CCK-8), a gut-brain peptide, regulates a variety of physiological behavioral processes. Previously, we reported that exogenous CCK-8 attenuated morphine-induced conditioned place preference, but the possible effects of CCK-8 on aversively motivated drug seeking remained unclear. To investigate the effects of endogenous and exogenous CCK on negative components of morphine withdrawal, we evaluated the effects of CCK receptor antagonists and CCK-8 on the naloxone-precipitated withdrawal-induced conditioned place aversion (CPA). The results showed that CCK2 receptor antagonist (LY-288,513, 10 µg, i.c.v.), but not CCK1 receptor antagonist (L-364,718, 10 µg, i.c.v.), inhibited the acquisition of CPA when given prior to naloxone (0.3 mg/kg) administration in morphine-dependent rats. Similarly, CCK-8 (0.1–1 µg, i.c.v.) significantly attenuated naloxone-precipitated withdrawal-induced CPA, and this inhibitory function was blocked by co-injection with L-364,718. Microinjection of L-364,718, LY-288,513 or CCK-8 to saline pretreated rats produced neither a conditioned preference nor aversion, and the induction of CPA by CCK-8 itself after morphine pretreatments was not significant. Our study identifies a different role of CCK1 and CCK2 receptors in negative affective components of morphine abstinence and an inhibitory effect of exogenous CCK-8 on naloxone-precipitated withdrawal-induced CPA via CCK1 receptor.