What is Which of the following is not true about the mechanism of action of benzodiazepines? and explain in detail?
Ans. is 'd' i.e., It has GABA mimetic action Mechanism of action of benzodiazepines (BZDs)* Muscle relaxation is produced by action on medulla.* Ataxia is due to action on cerebellum.* BZDs acts on GABAA receptors.* GABAa receptor has 5 subunits a / b, b, a / g.* GABA binding site is on b. subunit, while BZDs binding site is on a / g subunit.* BZDs receptor increase the conductance of Cl channel.* BZDs do not themselves increase Cl conductance, i.e. they have only GABA facilitatory but no GABA mimetic action. (Barbiturates have both GABA facilitatory and GABA mimetic actions).Effect on CNS* In contrast to barbiturates, BZDs are not general depressant, but exert relatively selective anxiolytic, hypnotic, muscle relaxant and anticonvulsant effects.* The antianxiety action of BZDs is not dependent on their sedative property - with chronic administration relief of anxiety is maintained, but drowsiness wanes off due to development of tolerance.* Stage 2 sleep is increased, while REM, Stage 3 & 4 sleep are decreased.* Nitrazepam is the only benzodiazepine, which increases REM sleep.* Clonazepan and diazepam have more marked muscle relaxant property.* Clonazepam, diazepam, nitrazepam and flurazepam have more prominent anticonvulsant activity than other BZDs.* Diazepam (but not other BZDs) has analgesic action.* Diazepam produces short lasting coronary dilatation on i.v. injection.* Diazepam decreases nocturnal gastric secretion and prevents stress ulcers.