Amphetamine and chlorpromazine modify cerebral insulin levels in rats

Antipsychotic-Induced Dysregulation of Glucose Metabolism Through the Central Nervous System: A Scoping Review of Animal Models

The use of antipsychotic drugs is associated with adverse metabolic effects. Disruptions in glucose metabolism such as hyperglycemia and insulin resistance have been shown to occur with antipsychotic use, independent of changes in body weight or adiposity. The regulation of whole-body glucose metabolism is partly mediated by the central nervous system. In particular, the hypothalamus and brainstem are responsive to peripheral energy signals and subsequently mediate feedback mechanisms to maintain peripheral glucose homeostasis. In this scoping review of preclinical in vivo studies, we aimed to explore central mechanisms through which antipsychotics dysregulate glucose metabolism. A systematic search for animal studies identified 29 studies that met our eligibility criteria for qualitative synthesis. The studies suggest that antipsychotic-induced changes in autonomic nervous system activity, certain neurotransmitter systems, expression of neuropeptides, and central insulin action mediate impairments in glucose metabolism. These findings provide insight into potential targets for the mitigation of the adverse effects of antipsychotics on glucose metabolism.

Phentermine induces conditioned rewarding effects via activation of the PI3K/Akt signaling pathway in the nucleus accumbens

RATIONALE

Phentermine is structurally similar to methamphetamine and is widely used as an anti-obesity drug in the USA and many other countries. The potential for reward of phentermine has been noted; however, the mechanisms of phentermine dependence have not been established.

OBJECTIVES

Here, we investigated the rewarding and dopaminergic behavioral responses to phentermine in mice and found that phentermine produced conditioned rewarding effects through the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in the nucleus accumbens (NAc).

METHODS

The impact of phentermine was assessed using conditioned place preference (CPP) test, climbing behavior test, and western blot analysis.

RESULTS

Phentermine 1 and 3 mg/kg (i.p.) significantly increased CPP. Phentermine, a known dopamine releaser, boosted apomorphine-induced climbing behavior in mice, and methamphetamine (i.p.) also increased apomorphine-induced dopaminergic behavior. Phentermine and methamphetamine increased the level of expression of the dopamine transporter (DAT) and phospho-Akt proteins to a similar degree in the NAc of CPP mice. To determine whether the conditioned rewarding effects of phentermine were mediated through the PI3K/Akt pathway, we assessed the effects of the Akt inhibitor LY294002 on phentermine-induced place preference and climbing behavior. LY294002 (1 and 3 μg/site, i.c.v.) reduced phentermine-induced CPP and phentermine-increased climbing behavior. However, LY294002 did not change CPP and climbing behavior itself and also did not decrease apomorphine-induced climbing behavior in mice. Further, LY294002 decreased the phentermine-increased levels of DAT protein and phosphorylation of Akt in the NAc of CPP mice.

CONCLUSIONS

Thus, these findings suggest that phentermine induces conditioned rewarding effects via activation of the PI3K/Akt signaling pathway in the NAc.

Increased incidence of neuroleptic-induced perioral movements in the rat by hyperglycemia

It has been suggested that Tardive dyskinesia (TD) is associated with abnormal glucose metabolism. To investigate further the issue the effects of alloxan-induced hyperglycemia on the incidence and severity of haloperidol-induced perioral movements were studied in the rat. Hyperglycemic rats showed significantly higher incidence and severity of rating of abnormal perioral movements than did control rats. Severity ratings of perioral movements were significantly correlated with blood glucose levels in the hyperglycemic rats. These findings suggest that hyperglycemia may increase the severity of neuroleptic-induced perioral movements, and support the possibility that glucose intolerance may increase the risk of TD.

Levels of insulin in the brains of rats modified by chronic administration of amphetamine, haloperidol and sulpiride

Rats treated with two classic neuroleptic drugs at therapeutic doses, haloperidol (0.05 mg/kg/day i.p.) and sulpiride (3 mg/kg/day i.p.) showed a marked decline in cerebral levels of insulin (0.085 +/- 0.02 ng/g and 0.120 +/- 0.04 ng/g wet weight respectively) compared to the control group (0.383 +/- 0.05 ng/g wet weight), while rats given D-amphetamine bitartrate chronically (20 mg/kg/day p.o.) showed an increase in cerebral insulin (0.55 +/- 0.04 ng/g wet weight). Combining treatment with each neuroleptic drug and amphetamine, at the same doses, produced a significant decrease in cerebral levels of insulin (P less than 0.001) as in the amphetamine animals. In the groups of rats treated with haloperidol, sulpiride and both of these drugs combined with amphetamine, there was a slight increase in levels of serum insulin, more so in the neuroleptic groups. Serum glucose values did not vary.