RAT-BRAIN MONOAMINE-OXIDASE-A AND MONOAMINE-OXIDASE-B INHIBITORY (TRIBULIN) ACTIVITY DURING DRUG-WITHDRAWAL ANXIETY

Morphine (10 mg/kg), ethanol (8% w/v, 2 ml/kg), nicotine (0.1 mg/kg), cannabis extract (200 mg/kg), lorazepam (10 mg/kg) and ondansetron (0. 1 mg/kg) were each administered to rats twice daily i.p, for 14 days a nd the anxiogenic response following their withdrawal was monitored by the elevated plus-maze test 24 h later. Brains were removed and endog enous monoamine oxidase (MAO) A and B inhibitory activity (tribulin) l evels measured on day 14 and 24 h after drug withdrawal in different g roups of animals. Morphine, ethanol, lorazepam and nicotine withdrawal was associated with significant anxiety and corresponding increase in brain tribulin activity, particularly its MAO A inhibitory component. Cannabis and ondansetron withdrawal were neither associated with anxi ety or change in tribulin levels. The investigation supports the postu lated role of tribulin as an endogenous correlate of anxiety, its MAO A inhibitory component accounting for a major part of this effect.