Effects of benzodiazepine receptor agonists in neurones acutely dissociated from the rat neostriatum

Multiple effects of bisphenol A, an endocrine disrupter, on GABAA receptors in acutely dissociated rat CA3 pyramidal neurons

Bisphenol A (BPA), an endocrine disrupter, is contained in cans, polycarbonate bottles and some dental sealants. While the toxicological effects of BPA on the endocrine system have been extensively studied, its action on the central nervous system is poorly understood. Herein, we report the effects of BPA on GABA-induced currents (I(GABA)), using a conventional whole-cell patch clamp technique from acutely isolated rat CA3 pyramidal neurons. By itself, BPA concentration-dependently elicited the membrane current, which was significantly blocked by bicuculline, a selective GABA(A) receptor antagonist. BPA potentiated the peak I(GABA) induced by lower concentrations of GABA (<10 microM) in a concentration-dependent manner. The extent of BPA-induced potentiation of I(GABA) was significantly reduced by either diazepam or ethanol, allosteric modulators of GABA(A) receptors. BPA, however, inhibited the peak I(GABA) induced by higher concentrations of GABA (>30 microM), and accelerated the desensitization rate of I(GABA). BPA also greatly inhibited the steady state I(GABA) induced by higher concentrations of GABA (>30 microM) in a noncompetitive manner. In addition, BPA affected synaptic GABA(A) receptors as it decreased the amplitude of GABAergic miniature inhibitory postsynaptic currents in a concentration-dependent manner. Considering its complex modulatory effects on GABA(A) receptors, BPA might have potential toxicological effects on the central nervous system.

Zopiclone, but not brotizolam, impairs memory storage during sleep

We compared the effect of a single bedtime dose of two short half-time hypnotics, brotizolam (0.25 mg) and zopiclone (7.5 mg), on memory storage during sleep in a double blind, placebo-controlled, three-way crossover design trial in eight healthy volunteers. Memory was evaluated using a standard word list free-recall test learned before the bedtime dose by the subjects, who were asked to remember the list the following morning. Digit Symbol Substitution Test revealed no residual sedation by brotizolam or zopiclone. Brotizolam did not affect the morning recall compared to placebo, but subjects remembered less words under zopiclone treatment, suggesting that this drug could affect memory storage during sleep.

Role of platelet activating factor in triazolobenzodiazepines-induced retrograde amnesia

Benzodiazepine (diazepam), triazolobenzodiazepines (brotizolam, triazolam) and platelet activating factor (PAF) antagonist (BN 52021) are administered to mice before acquisition and retrieval trials conducted using Morris water maze. Benzodiazepine has produced only anterograde amnesia and it has not produced retrograde amnesia. Triazolobenzodiazepines have produced both anterograde and retrograde amnesia. PAF antagonist (BN 52021) has only produced retrograde amnesia and it has not produced anterograde amnesia. The anterograde amnesia produced by benzodiazepine and triazolobenzodiazepines, has been prevented by benzodiazepine receptor antagonist (flumazenil). It suggests that benzodiazepine- and triazolobenzodiazepines-induced anterograde amnesia may be mediated through benzodiazepine receptors. On the other hand, retrograde amnesia produced by PAF antagonist (BN 52021) and triazolobenzodiazepines has been attenuated by PAF and PAF acetyl hydrolase inhibitors such as cigarette smoke extract (CSE) and phenylmethanesulfonylflouride. It suggests that triazolobenzodiazepine-induced retrograde amnesia may be mediated through blockade of PAF receptors.

Temperature-dependent effect of zolpidem on the GABAA receptor-mediated response at recombinant human GABAA receptor subtypes

The effects of zolpidem on the two forms of recombinant human GABAA receptors (alpha1beta2gamma2s and alpha3beta2gamma2s) at different temperatures were functionally investigated, using the whole-cell patch recording configuration. In both forms, zolpidem potentiated the response to GABA in a concentration-dependent manner. At 16 degrees C, the apparent dissociation constant (KD) values for the alpha1beta2gamma2s and alpha3beta2gamma2s forms were 3.7 x 10(-8) and 5.6 x 10(-7) M, respectively. When the temperature was increased to 36 degrees C, the KD values for the alpha1beta2gamma2s and alpha3beta2gamma2s forms were 2.1 x 10(-7) and 1.5 x 10(-6) M, respectively. Although the affinity ratio was reduced from 15.1 to 7.1-fold the selectivity of zolpidem for the alpha1beta2gamma2s still remained at 36 degrees C.