Anxiolytic-like effects of meprobamate. Interactions with an opiate antagonist in Swiss and BALB/c mice

µ-Opioid receptor antagonism facilitates the anxiolytic-like effect of oxytocin in mice

Mood and anxiety disorders are leading causes of disability worldwide and are major contributors to the global burden of diseases. Neuropeptides, such as oxytocin and opioid peptides, are important for emotion regulation. Previous studies have demonstrated that oxytocin reduced depression- and anxiety-like behavior in male and female mice, and opioid receptor activation reduced depression-like behavior. However, it remains unclear whether the endogenous opioid system interacts with the oxytocin system to facilitate emotion regulation in male and female mice. We hypothesized that opioid receptor blockade would inhibit the anxiolytic- and antidepressant-like effects of oxytocin. In this study, we systemically administered naloxone, a preferential μ-opioid receptor antagonist, and then intracerebroventricularly administered oxytocin. We then tested mice on the elevated zero maze and the tail suspension tests, respective tests of anxiety- and depression-like behavior. Contrary to our initial hypothesis, naloxone potentiated the anxiolytic-like, but not the antidepressant-like, effect of oxytocin. Using a selective μ-opioid receptor antagonist, D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2, and a selective κ-opioid receptor antagonist, norbinaltorphimine, we demonstrate that μ-opioid receptor blockade potentiated the anxiolytic-like effect of oxytocin, whereas κ-opioid receptor blockade inhibited the oxytocin-induced anxiolytic-like effects. The present results suggest that endogenous opioids can regulate the oxytocin system to modulate anxiety-like behavior. Potential clinical implications of these findings are discussed.

Iron-Catalyzed Reaction of Urea with Alcohols and Amines: A Safe Alternative for the Synthesis of Primary Carbamates

A general study of the iron-catalyzed reaction of urea with nucleophiles is here presented. The carbamoylation of alcohols allows for the synthesis of N-unsubstituted (primary) carbamates, including present drugs (Felbamate and Meprobamate), without the necessity to apply phosgene and related derivatives. Using amines as nucleophiles gave rise to the respective mono- and disubstituted ureas via selective transamidation reaction. These atom-economical transformations provide a direct and selective access to valuable compounds from cheap and readily available urea using a simple Lewis-acidic iron(II) catalyst.

Effects of lactational exposure to benzo[alpha]pyrene (B[alpha]P) on postnatal neurodevelopment, neuronal receptor gene expression and behaviour in mice

The harmful effects of exposure to benzo[alpha]pyrene (B[alpha]P), which is a neurotoxic pollutant, on mammalian neurodevelopment and/or behaviour as yet remain widely unclear. In the present investigation, we evaluated the impact of the lactational exposure to B[alpha]P on postnatal development of pups and behaviour of young mice. The neurobiological effects of B[alpha]P during lactation were also evaluated on pups' brain. Here, we found that lactational exposure to B[alpha]P at 2 and 20mg/kg affects the neuromaturation of pups by significantly decreasing their reflex as highlighted in surface righting reflex and negative geotaxis tests. However, we noted a significant increase in muscular strength of lactationally B[alpha]P mg/kg-exposed pups, which was probably due to the impact of the exposure to this toxic compound on body weight gain. At the pup stage, lactational exposure to B[alpha]P also provoked a neurobiological change, which was assessed by determination of neuronal receptor gene expression. Indeed, a significant reduction in gene expression of 5HT(1A) receptors in pups exposed to B[alpha]P through lactation was found in comparison to controls. Additionally, attenuation in the expression of MOR(1) mRNA was observed, but statistically significant only in animals receiving the higher dose. Neither the expression levels of ADRA(1D) nor GABA(A) mRNA were altered. Interestingly, the harmful effects of lactational exposure to B[alpha]P on behaviour and cognitive function were still found despite a long post-weaning period. Young mice whose mothers were exposed to B[alpha]P displayed a disinhibition behaviour towards the aversive spaces of the elevated plus maze. Furthermore, a significant increase of spontaneous alternation in the Y-maze was observed, but only in young mice whose mothers were orally exposed to the lower dose of B[alpha]P. Our results suggest a close link between the neurobiological change highlighted in pups' brain and the different behavioural disturbances observed during postnatal development period until young adult stage.

Endogenous opiates: 2000

This paper is the twenty-third installment of the annual review of research concerning the opiate system. It summarizes papers published during 2000 that studied the behavioral effects of the opiate peptides and antagonists, excluding the purely analgesic effects, although stress-induced analgesia is included. The specific topics covered this year include stress; tolerance and dependence; learning, memory, and reward; eating and drinking; alcohol and other drugs of abuse; sexual activity, pregnancy, and development; mental illness and mood; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; gastrointestinal, renal, and hepatic function; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Naloxone potentiates anxiolytic-like actions of diazepam, pentobarbital and meprobamate but not those of Ro19-8022 in the rat

The elevated plus-maze test was used to determine if the opiate antagonist naloxone could potentiate the anxiolytic-like effects of the benzodiazepine diazepam, the barbiturate pentobarbital, the propanediol carbamate meprobamate and the partial benzodiazepine receptor agonist [R]-1-[(10-chloro-4-oxo-3-phenyl-4H-benzo[a]quinolizin-1-yl) carbonyl]-2-pyrrolidine-methanol (Ro19-8022) in the rat. A subeffective dose of each of these compounds was combined with naloxone, 10 mg/kg. Naloxone had no effect by itself, but potentiated all drugs except Ro19-8022. The proportion of entries on the open arm increased while the total number of arms entries was not modified. These results coincide with and extend data previously obtained in the mouse. One possible explanation for naloxone's effect could be that it blocks opioid inhibition of GABAergic (gamma-aminobutyric acid) neurons thereby enhancing the effects of benzodiazepines. Another possibility is that naloxone blocks opioid effects on adenosinergic systems.