Beta-carbolines characterized as benzodiazepine receptor agonists and inverse agonists produce bi-directional changes in palatable food consumption

Drugs which bind to specific benzodiazepine recognition sites fall into three categories: agonists, antagonists, and inverse agonists. A set of biochemical parameters is available which distinguishes between the three. In addition, actions of the drugs result in physiological and behavioural effects which are distinguishable. beta-Carboline derivatives provide a group of compounds which show high affinity for the benzodiazepine sites, and which contains examples belonging to each of the three categories. Evidence is reviewed which shows that beta-carboline benzodiazepine receptor agonists (ZK 93423, ZK 91296) produce increases in the consumption of a palatable diet by non-deprived rats, that beta-carboline inverse agonists (FG 7142, DMCM) produce an anorectic effect, and that the beta-carboline ZK 93426 acts as a benzodiazepine receptor antagonist. The results support the proposal of bi-directional control of feeding responses through the action of drugs at a common benzodiazepine receptor. Furthermore, benzodiazepine receptor inverse agonists provide a novel class of anorectic agents. Evidence is also reviewed which is suggestive of the modulation of food-related reward by drug actions at benzodiazepine receptors.