Beta-carbolin at benzodiazepine receptors acts as

Ans. c (Inverse agonist) (Ref. KDT 6th/ 395)INVERSE AGONISTS# An inverse agonist is an agent which binds to the same receptor binding-site as an agonist for that receptor but exerts the opposite pharmacological effect.# E.g.:- R015-4513 which is the inverse agonist of the benzodiazepine .- Gabapentin acts by facilitation of GABA-mediated CT channel opening. It does not block GABA receptors. Substances called beta-carboline which also bind this receptor cause stimulation anxiety, increased muscle tone and convulsions. They are inverse agonists of benzodiazepine receptors.Agonistsincrease the inhibitory transmitter GABA potencyInverse agonistsdecrease GABA potencyAntagonistsblock action of agonists. Drugs affecting GABAA-receptor gated chloride channel# GABA: Endogenous agonist at GABAA receptor - promotes Cl- influx# Buscimol: Agonist at GABAA site# Bicuculline: Competitive antagonist at GABAA receptor# Barbiturate: Agonist at an allosteric site (Ppicrotoxin site); prolong GABA action; open CI- channel# Alcohol, inhalational anaesthetics, Propofol: Open CI- channel directly; allosteric facilitation of GABA# Benzodiazepine: Agonist at an allosteric BZD site --^facilitate GABA action# b-Carboline (DMCM): Inverse agonist at BZD site ->>impede GABA action# Flumazenil: Competitive antagonist at BZD site