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Barbiturate tolerance: effects on GABA-operated chloride channel function

Barbiturate tolerance: effects on GABA-operated chloride channel function

  1. Bajeda
    Allan AM, Zhang X, & Baier LD. (1992). Barbiturate tolerance: effects on GABA-operated chloride channel function. Brain Research, 588(2):255-60.

    Abstract: Male ICR mice were fed powdered laboratory chow containing phenobarbital for 7 days to induce tolerance. Mice were sacrificed and brains assayed for changes in GABA-mediated chloride flux into membrane vesicles (microsacs). Concentration-dependent stimulation of chloride flux by GABA alone was not affected by the development of tolerance of phenobarbital. Phenobarbital potentiation of GABA-mediated chloride flux was significantly attenuated in the membranes prepared from phenobarbital-tolerant mice compared with those from pair-fed control mice. Similarly, stimulation of GABA-mediated flux by the benzodiazepine, flunitrazepam was also depressed in membranes from tolerant mice. However, the ability of ethanol and the benzodiazepine inverse agonist FG-7142 to modulate GABA-gated chloride flux was not affected by the development of phenobarbital tolerance. No significant changes in saturation [3H]diazepam binding parameters were observed. These findings suggest that there is a degree of cross-tolerance between phenobarbital and benzodiazepine agonist at the level of the GABA-operated chloride channel. Furthermore, although some reports have demonstrated behavioral cross-tolerance between ethanol and barbiturates, the present data suggest different mechanisms of tolerance development for these intoxicants at the level of the GABAA receptor chloride channel complex.