Combined use of alcohol and cigarette increases locomotion and glutamate levels in the cerebrospinal fluid without changes on GABAA or NMDA receptor subunit mRNA expression in the hippocampus of rats

The distinct roles of various neurotransmitters in modulating methamphetamine-induced conditioned place preference in relevant brain regions in mice

OBJECTIVES

Previous studies have shown that methamphetamine (METH) can induce complex adaptive changes in the reward system in the brain, including the changes in the content of neurotransmitters in the signal transduction pathway. However, how the changes of various neurotransmitters in relevant brain reward circuits contribute to METH-induced conditioned place preference (CPP) remains unclear.

METHODS

In this study, first, we designed an animal model of METH-induced CPP. Then we used liquid chromatography-mass spectrometry (LC-MS) to simultaneously determine the contents of various neurotransmitters - dopamine (DA), norepinephrine (NE), 5-hydroxytryptamine (5-HT), 5-hydroxyindole acetic acid (5-HIAA), glutamic acid (Glu) and glutamine (Gln) - in different brain regions of the prefrontal cortex (PFc), nucleus accumbens (NAc), caudate-putamen (CPu) and hippocampus (Hip), which are believed to be relevant to the drug's reward effect.

RESULTS

The results of the behavioral experiment suggested that 1.0 mg/kg METH could induce obvious CPP in mice. The results about various neurotransmitters showed that: DA significantly increased in NAc in the METH group; Glu increased significantly in the METH group in PFc and NAc and Gln increased significantly in the METH group in PFc.

CONCLUSIONS

These results suggested that the neurotransmitters of DA, Glu and Gln may work together and play important roles in METH-induced CPP in relevant brain reward circuits, especially in PFc and NAc. These findings therefore could help to advance the comprehensive understanding of the neurochemic and psychopharmacologic properties of METH in reward effect, which is important for future improvements in the treatment of drug addiction.

Low-cost apparatus for cigarette smoke exposure in rats

BACKGROUND

The effects of tobacco smoke on the central nervous system are usually studied with isolated nicotine, ignoring other compounds present in cigarette smoke. The few studies that use in vivo whole-body cigarette smoke exposure are usually performed in expensive commercial apparatus.

NEW METHOD

We presented a feasible, safe, and low-cost apparatus for cigarette smoke exposure in rodents.

RESULTS

Rats exposed to cigarette smoke in this apparatus showed cotinine levels similar to human active smokers. Additional results showed that cigarette smoke exposure increased glutamate and aspartic acid levels and decreased leucine, isoleucine, ornithine, phenylalanine, and tryptophan levels in the cerebrospinal fluid of rats.

COMPARISON WITH EXISTING METHOD(S)

Our apparatus is feasible, safe, and costs 67-fold less than a commercial automatized smoking machine. Beyond the low cost, it does not require specialized knowledge for building or maintenance.

CONCLUSIONS

We concluded that our low-cost apparatus is reliable and reproduces cigarette smoke use in humans.

Hepatic and renal damage by alcohol and cigarette smoking in rats

Chronic use of alcohol and tobacco cigarettes is associated to millions of deaths per year, either by direct or indirect causes. However, few studies have explored the additional risks of the combined use of these drugs. Here we assessed the effect of the combined use of alcohol and cigarette smoke on liver or kidney morphology, and on biochemical parameters in chronically treated rats. Male Wistar rats were allocated to receive 2 g/kg alcohol orally, which was followed by the inhalation of smoke from six cigarettes during 2 h (ALTB group) for 28 days. Other groups received alcohol alone (AL) or were exposed to cigarette smoke (TB) alone and were compared to control (CT) rats, which received water followed by ambient air. On day 29, rats were euthanized and blood samples were collected for aminotransferase enzymes (AST and ALT), creatinine, and urea analysis. Liver and kidney were weighted, dissected, fixed, and stained with hematoxylin and eosin for morphological analysis. Our results showed that necrosis was elevated in the AL, TB, and mainly the ALTB group in both liver and kidney of rats. Serum levels of AST and ALT were reduced by cigarette smoke exposure, independently of alcohol use. Serum creatinine levels increased after tobacco smoke exposure. On the other hand, TB and AL groups decreased serum urea levels, and their association restored that decrease. Absolute liver and kidney weights were lower in the cigarette smoke exposure rats. Lastly, body weight gain was lower in TB group and combined use restored it. Thus, we may infer that the use of alcohol, exposure to tobacco cigarette smoke or, mainly, their association promotes liver and kidney injuries, and this damage is related with biochemical changes in rats.