Laboratory diagnosis of toluene-based inhalants abuse

Effects of drugs of abuse on channelrhodopsin-2 function

Channelrhodopsins are light activated ion channels used extensively over the past decade to probe the function of genetically defined neuronal populations and distinct neural circuits with high temporal and spatial precision. The widely used Channelrhodopsin-2 variant (ChR2) is an excitatory opsin that undergoes conformational changes in response to blue light, allowing non-selective passage of protons and cations across the plasma membrane thus leading to depolarization. In the addiction neuroscience field, opsins such as ChR2 provide a means to disambiguate the overlapping circuitry involved in mediating the reinforcing and aversive effects of drugs of abuse as well as to determine the plasticity that can occur in these circuits during the development of dependence. Although ChR2 has been widely used in animal models of drug and alcohol self-administration, direct effects of drugs of abuse on ChR2 function may confound its use and lead to misinterpretation of data. As a variety of neuronal ion channels are primary targets of various drugs of abuse, it is critical to determine whether ChR2-mediated currents are modulated by these drugs. In this study, we performed whole-cell electrophysiological recordings in HEK293 cells expressing the commonly used ChR2(H134R) variant and examined the effects of various drugs of abuse and other commonly used agents on light-induced currents. We found no differences in ChR2-mediated currents in the presence of 30 μM nicotine, 30 μM cocaine, 100 μM methamphetamine or 3 mM toluene. Similarly, ChR2 currents were insensitive to 30 mM ethanol but higher concentrations (100-300 mM) produced significant effects on the desensitization and amplitude of light-evoked currents. Tetrahydrocannabinol (1-10 μM) and morphine (30-100 μM) significantly inhibited ChR2 currents while the cannabinoid receptor antagonist AM-251 had no effect. The sodium channel blocker tetrodotoxin (5 μM) and the generic channel blocker/contrast agent gadolinium chloride (10 mM) also reduced ChR2 currents while the divalent ion magnesium (10 mM) had no effect. Together, the results from this study highlight the importance of conducting appropriate control experiments when testing new compounds in combination with optogenetic approaches.

Toluene disruption of the functions of L1 cell adhesion molecule at concentrations associated with occupational exposures

BACKGROUND

Prenatal toluene exposure can cause neurodevelopmental disabilities similar to fetal alcohol syndrome. Both share neuroanatomic pathologies similar to children with mutations in L1 cell adhesion molecule (L1). L1 mediates neurite outgrowth (NOG) via signaling through ERK1/2, which require trafficking of L1 through lipid rafts. Our objective is to determine if toluene inhibits L1-mediated NOG and toluene inhibits L1 signaling at concentrations achieved during occupational exposure.

METHODS

Concentrations of toluene reflective of blood concentrations achieved in solvent abusers and occupational settings are used. Cerebellar granule neurons (CGN) harvested from postnatal day 6 rat pups are plated on coverslips coated with poly-L-lysine (PLL) alone or PLL followed by laminin. L1 is added to the media of CGN plated on PLL alone. Toluene is added 2 h after plating. Cells are fixed at 24 h and neurite length is measured. ERK1/2 activation by L1 in CGN is analyzed by immunoblot.

RESULTS

Toluene significantly reduced mean neurite length of CGN exposed to L1 but not laminin. Toluene significantly reduced L1-mediated ERK1/2 phosphorylation.

CONCLUSION

Results suggest that toluene inhibits L1-lipid raft interactions at occupationally relevant concentrations and may lead to a fetal solvent spectrum disorder similar to fetal alcohol spectrum disorder.

Laboratory approach for diagnosis of toluene-based inhalant abuse in a clinical setting

The steady increase of inhalant abuse is a great challenge for analytical toxicologists. This review describes an overview of inhalant abuse including the extent of the problem, types of products abused, modes of administration, pharmacology and effects of inhalants, the role of laboratory, interpretation of laboratory results and clinical considerations. Regular laboratory screening for inhalant abuse as well as other substance abuse and health risk behaviors must be a part of standard clinical care.

The Health Profile of Street Children in Africa: A Literature Review

The United Nations Children's Fund has labeled street children as children in difficult circumstances, which represent a minority population that has been under-represented for too long in health research. This is a concern because street children are at risk of carrying a greater disease burden. Their homeless lifestyle makes them more vulnerable to health risks and problems than children who live at home; as they roam the streets begging for food and money to obtain basic needs and are found sleeping in half-destroyed houses, abandoned basements, under bridges and in the open air. This paper presents health results from a systematic review of literature from 17 databases and including 16 countries in Africa. The review revealed that there are more boys than girls living on the street in their adolescence and who mainly have left home due to poverty and abuse. These children in these countries are vulnerable to poor health due to factors such as homelessness, risky sexual behavior, substance abuse and violence. Among the health problems identified are growth and nutritional disorders, physical injuries, violence, sexual abuse, communicable diseases including diarrheal diseases, malaria, respiratory diseases, neglected tropical diseases, mental health issues, substance abuse, reproductive health disorders, mortality, sexually transmitted diseases and HIV/AIDS. Primary interventions that could prevent poor health and improve the health status of street children include provision of safe shelter, proper nutrition, access to health care, health education, and sexual reproductive health, protection from any form of abuse, violence and substance abuse. Enforcing state policies and laws in all African countries is required to protect street children from neglect, abuse and to increase their access to education. More research on the health risks and health status of street children is still required, particularly in Sub-Saharan Africa, which carries the greatest disease burden and poverty.

The health status of street children and youth in low- and middle-income countries: a systematic review of the literature

The health of the tens of millions of street children globally is understudied. We undertook a systematic review of the existing quantitative literature regarding the health status of street children and youth in low- and middle-income countries to summarize available knowledge, identify underexplored areas of research, and inform the future research agenda regarding the health of this population. A total of 108 articles met our inclusion criteria. Demographic data and structural factors associated with street life are summarized. Although data in specific regions or diseases are sparse, the literature review illustrates that youth's survival behaviors and the exposures associated with poor shelter have resulted in disproportionate morbidity in the areas of infectious illness, psychiatric disease, reproductive health, and perhaps to a lesser extent, growth. Vast areas of health that may disproportionately affect street children in childhood or later on as adults have not been investigated, including chronic diseases and cognitive deficits. Studies of specific diseases or conditions vary considerably by region. Strengths and limitations of the literature are discussed and principles for future research in this area are proposed.

Anxiety symptoms in crack cocaine and inhalant users admitted to a psychiatric hospital in southern Brazil

OBJECTIVE

The occurrence of psychiatric comorbidity among individuals with crack or inhalant dependence is frequently observed. The objective of this study was to investigate anxiety symptoms among crack cocaine and inhalant users in southern Brazil.

METHODS

The study investigated two groups of volunteers of equal size (n=50): one group consisted of crack cocaine users, and the other group consisted of inhalant users. Research volunteers completed the Portuguese versions of the State-Trait Anxiety Inventory (STAI), Hamilton Anxiety Rating Scale (HAM-A), and Self-Report Questionnaire (SRQ).

RESULTS

Both crack and inhalant users experience significant symptoms of anxiety. Inhalant users presented significantly more anxiety symptoms than crack users according to the HAM-A questionnaire only. In contrast to the results of the HAM-A, the STAI failed to demonstrate a significant difference between the two groups of substance users. SRQ scores revealed that crack and inhalants users had significant degrees of morbidity.

CONCLUSION

A significant difference regarding anxiety symptomatology, especially state anxiety, was observed among inhalant and crack users. Anxiety and overall mental psychopathology were significantly correlated in this sample. The results indicate that screening initiatives to detect anxiety and additional psychiatric comorbidities among crack and inhalant users are feasible and relevant.

Reproductive toxicology and teratology of abused toluene

Toluene is an organic solvent that is widely used by industry and is ubiquitous in our environment. As a result, exposure to solvents like toluene in work-related settings (i.e., relatively constant, low-level exposures) or through inhalant abuse (i.e., relatively intermittent, high-level exposures) is increasing for many women of reproductive age. Evidence suggests that the risk for pregnancy problems, as well as developmental delays and neurobehavioral difficulties, is higher for the children of women who have been exposed to high concentrations of organic solvents during pregnancy than for those who have not. These risks appear to be higher in cases of abuse exposure to solvents such as toluene, particularly in comparison to the risk for teratogenic outcomes with occupational solvent exposure. Despite this, the reproductive toxicology and teratology following abuse of toluene and other inhalants remains under-investigated. This brief review describes the current state of our understanding of the reproductive and teratogenic risk of gestational toluene abuse. The data to date suggest that the high levels of toluene exposure typical with inhalant abuse are more detrimental to fetal development than typical occupational exposure, and preclinical paradigms can be beneficial for investigating the processes and risks of prenatal solvent exposure. While substantial research has been done on the reproductive effects of occupational exposures to organic solvents, more research is needed on the outcomes and mechanisms of exposures typical of inhalant abuse.

Toluene-impaired drivers: behavioral observations, impairment assessment, and toxicological findings

Toluene is an aromatic hydrocarbon solvent frequently abused for its euphoric and intoxicating properties. This report describes a series of six cases involving drivers arrested for driving under the influence who subsequently tested positive for toluene. Case data including driving behavior, physiological signs and symptoms, evidence of impairment, and toxicology findings were reviewed. Blood toluene concentrations in the drivers ranged from 12 to 45 mg/L (median 23 mg/L, mean 25 mg/L, SD 12.1 mg/L). All drivers were determined to be intoxicated, and displayed symptoms including balance problems, confusion and disorientation, loss of coordination, and inability to follow instructions. They also displayed horizontal but not vertical nystagmus, elevated pulse and blood pressure, and lower body temperature. These findings are consistent with prior reports that subjects with blood toluene concentrations above 10 mg/L are invariably under the influence and their driving skills are affected.

Characterization of an inhaled toluene drug discrimination in mice: effect of exposure conditions and route of administration

The drug discrimination procedure in animals has been extensively utilized to model the abuse related, subjective effects of drugs in humans, but it has seldom been used to examine abused volatile inhalants like toluene. The present study sought to characterize the temporal aspects of toluene's discriminative stimulus as well assess toluene blood concentrations under identical exposure conditions. B6SJLF1/J mice were trained to discriminate 10 min of exposure to 6000 ppm inhaled toluene vapor from air. Toluene vapor concentration dependently substituted for the training exposure condition with longer exposures to equivalent concentrations producing greater substitution than shorter exposures. Toluene's discriminative stimulus effects dissipated completely by 60 min after the cessation of exposure. Injected liquid toluene dose-dependently substituted for toluene vapor as well as augmenting the discriminative stimulus effects of inhaled toluene. Toluene blood concentrations measured under several exposure conditions which produced full substitution were all nearly identical suggesting that the concentration of toluene in the animal tissues at the time of testing determined discriminative performance. These results indicate that the discriminative stimulus effects of inhaled toluene vapor are likely mediated by CNS effects rather than by its pronounced peripheral stimulus effects.