N-Methyl-beta-carboline-3-carboxamide (FG 7142), an anxiogenic agent in airborne particles and cigarette smoke-polluted indoor air

Effects of the benzodiazepine inverse agonist FG7142 on the structure of anxiety-related behavior of male Wistar rats tested in hole board

RATIONALE

Little is known about the structural characteristics of the behavior of rats with enhanced anxiety level. To fill this gap, a study was undertaken where effects of an anxiogenic drug were examined on behavioral structure of rats tested in hole board.

OBJECTIVES

This study investigates effects of increased anxiety level on the structure of the behavior of rats tested in hole board METHODS: Different doses of FG7142 (1, 4, 8 mg/kg IP), a potent anxiety-inducing drug, were administered to three groups of male Wistar rats. A further group was administered saline. Experiments were recorded through a digital camera. Quantitative and multivariate approaches were applied.

RESULTS

Percent distributions and durations showed increases of immobile sniffing, rearing, head dip, and edge sniff and a significant reduction of grooming activities and of walking. In addition, a decrease of head dip/edge sniff ratio was detected. Transition matrices evidenced that FG7142 provoked evident modifications of behavioral structure mainly of general exploration of environment and focused exploration of the hole. Finally, adjusted residuals showed a reduced effectiveness of FG7142 on transitions from head dip to edge sniff; on the contrary, transitions from edge sniff to head dip underwent evident dose-dependent changes.

CONCLUSIONS

Present study provides a useful tool to analyze behavioral responses to different anxiety conditions. Accordingly, it is demonstrated that a condition of increased anxiety deeply modifies the structure of male Wistar rat's behavior in hole board. In addition, our results suggest that evaluation of head dip/edge sniff ratio can be considered a reliable index to appraise effects of pharmacological manipulation of anxiety and related behavioral elements.

Pharmacology of the beta-carboline FG-7,142, a partial inverse agonist at the benzodiazepine allosteric site of the GABA A receptor: neurochemical, neurophysiological, and behavioral effects

Given the well-established role of benzodiazepines in treating anxiety disorders, beta-carbolines, spanning a spectrum from full agonists to full inverse agonists at the benzodiazepine allosteric site for the GABA(A) receptor, can provide valuable insight into the neural mechanisms underlying anxiety-related physiology and behavior. FG-7,142 is a partial inverse agonist at the benzodiazepine allosteric site with its highest affinity for the alpha1 subunit-containing GABA(A) receptor, although it is not selective. FG-7,142 also has its highest efficacy for modulation of GABA-induced chloride flux mediated at the alpha1 subunit-containing GABA(A) receptor. FG-7,142 activates a recognized anxiety-related neural network and interacts with serotonergic, dopaminergic, cholinergic, and noradrenergic modulatory systems within that network. FG-7,142 has been shown to induce anxiety-related behavioral and physiological responses in a variety of experimental paradigms across numerous mammalian and non-mammalian species, including humans. FG-7,142 has proconflict actions across anxiety-related behavioral paradigms, modulates attentional processes, and increases cardioacceleratory sympathetic reactivity and neuroendocrine reactivity. Both acute and chronic FG-7,142 treatment are proconvulsive, upregulate cortical adrenoreceptors, decrease subsequent actions of GABA and beta-carboline agonists, and increase the effectiveness of subsequent GABA(A) receptor antagonists and beta-carboline inverse agonists. FG-7,142, as a partial inverse agonist, can help to elucidate individual components of full agonism of benzodiazepine binding sites and may serve to identify the specific GABA(A) receptor subtypes involved in specific behavioral and physiological responses.

Potential neurotoxic "agents provocateurs" in Parkinson's disease

Idiopathic Parkinson's disease (PD), one of the most common neurodegenerative disorders associated with aging, is characterized neurochemically by abnormal and profound loss of nigrostriatal dopamine (DA) neurons. A prominent current view is that the excessive degeneration of the dopaminergic system is the outcome of extended insults by environmental neurotoxins or endogenous neurotoxic factors in genetically vulnerable or susceptible individuals. Recent insights into the identities and mechanisms of potential neurotoxic species, which span pesticides, environmental contaminants including heterocyclic amines with beta-carboline (betaC) and isoquinoline (IQ) structures, endogenous DA metabolites or intermediates, neuromelanin, metals, and infectious agents, are presented.

Evaluation of exposure level of N-methyl-beta-carboline-3-carboxamide (FG 7142), an anxiogenic agent in humans

beta-Carboline-3-carboxylic acid methylamide (FG 7142), an anxiogenic agent, has been detected in human urine. The urinary excretion level of FG 7142 in non-smokers was found to be 0.503 +/- 0.25 ng per day (mean +/- S.D., n=10), while that in smokers was found to be 2.418 +/- 0.384 ng per day (n=10). This suggests that humans are exposed to FG 7142 and that smokers are exposed to higher levels of FG 7142 than non-smokers. Considering the previous findings that FG 7142 is present in cigarette smoke, indoor and outdoor air and smoke condensate of tree leaves, humans may be exposed to FG 7142 via the airways and lungs, although we cannot exclude the possibility of exposure via foodstuffs. Results of animal experiments suggest that FG 7142 which enters the bloodstream is excreted into the urine via the kidneys within 24 h in an unchanged form. Therefore, monitoring the level of FG 7142 in urine may be useful for monitoring the exposure level of FG 7142.