Metabotropic glutamate receptor 5 modulates behavioral and hypothermic responses to toluene in rats

A novel approach of substitution therapy with inhalation of essential oil for the reduction of inhalant craving: A double-blinded randomized controlled trial

Inhalants, which are neurotoxic central nervous system (CNS) suppressants, are frequently abused by young adults. Unlike other CNS depressants, including alcohol and opiates, no treatment is currently approved for inhalant dependence. In this report, a novel approach of substitution treatment for inhalant addiction was explored in a double-blinded, randomized, controlled crossover design to examine the effects of inhalation of essential oil and perfume on the reduction of cue-induced craving for inhalant in thirty-four Thai males with inhalant dependence. The craving response was measured by the modified version of Penn Alcohol Craving Score for Inhalants (PACS-inhalants). The participants (mean age ± SE = 27.9 ± 1.4) in this trial had used inhalant for 5.8 ± 1.1 years. Cravings could be induced in all participants by visual cues as assessed by ^50% increases in inhalant craving levels. Generalized estimating equations showed a significant suppressant effect of essential oil, but not perfume, on the craving response as compared with baseline cue-induced craving. Moreover, essential oil, but not perfume, had significant effects on physiological responses including decreasing pulse rate. It is concluded that inhaling essential oil as a substitution treatment for inhalant may be used as part of treatment programs for reducing inhalant craving.

The group II metabotropic glutamate receptor agonist LY379268 reduces toluene-induced enhancement of brain-stimulation reward and behavioral disturbances

RATIONALE

Toluene, a widely abused solvent with demonstrated addictive potential in humans, hasbeen reported to negatively modulate N-methyl-D-aspartate receptors (NMDARs) and alter glutamatergicneurotransmission. The group II metabotropic glutamate receptor (mGluR) agonist LY379268 has beenshown to regulate glutamate release transmission and NMDAR function and block toluene-induced locomotorhyperactivity. However, remaining unknown is whether group II mGluRs are involved in the toluene-induced reward-facilitating effect and other behavioral manifestations.

OBJECTIVES

The present study evaluated the effects of LY379268 on toluene-induced reward enhancement, motor incoordination, recognition memory impairment, and social interaction deficits.

RESULTS

Our data demonstrated that LY379268 significantly reversed the toluene-induced lowering of intracranial self-stimulation (ICSS) thresholds and impairments in novel object recognition, rotarod performance, and social interaction with different potencies.

CONCLUSIONS

These results indicate a negative modulatory role of group II mGluRs in acute toluene-induced reward-facilitating and behavioral effects and suggest that group II mGluR agonists may have therapeutic potential for toluene addiction and the prevention of toluene intoxication caused by occupational or intentional exposure.

Review of toluene action: clinical evidence, animal studies and molecular targets

It has long been known that individuals will engage in voluntary inhalation of volatile solvents for their rewarding effects. However, research into the neurobiology of these agents has lagged behind that of more commonly used drugs of abuse such as psychostimulants, alcohol and nicotine. This imbalance has begun to shift in recent years as the serious effects of abused inhalants, especially among children and adolescents, on brain function and behavior have become appreciated and scientifically documented. In this review, we discuss the physicochemical and pharmacological properties of toluene, a representative member of a large class of organic solvents commonly used as inhalants. This is followed by a brief summary of the clinical and pre-clinical evidence showing that toluene and related solvents produce significant effects on brain structures and processes involved in the rewarding aspects of drugs. This is highlighted by tables highlighting toluene's effect on behaviors (reward, motor effects, learning, etc.) and cellular proteins (e.g. voltage and ligand-gated ion channels) closely associated the actions of abused substances. These sections demonstrate not only the significant progress that has been made in understanding the neurobiological basis for solvent abuse but also reveal the challenges that remain in developing a coherent understanding of this often overlooked class of drugs of abuse.