The effects of single and repeated administration of MAO inhibitors on acoustic startle response in rats.

In this paper the effects of single and repeated administration of brofaromine (BRO) and moclobemide (MOC)--monoamine oxidase A (MAO-A) inhibitors as well as deprenyl (DEP)--monoamine oxidase B (MAO-B) inhibitor on behavior of rats in acoustic startle response test were studied. For comparison the tricyclic antidepressant amitriptyline (AMI) was also studied. BRO given in a single dose of 10 mg/kg diminished the amplitude of acoustic startle response, while in a dose of 30 mg/kg had no effect. MOC diminished the amplitude when given in a single dose of 30 mg/kg, and had no effect in a dose of 10 mg/kg. Both MAO type A inhibitors diminished the startle reaction amplitude when tested 2 h after the last dose of a repeated treatment (twice daily for 14 days, 10 or 30 mg/kg, po). 5 days after the last dose the treatments did not affect the response. DEP given both in a single dose of 0.25 mg/kg and repeatedly for 15 and 21 days, increased the amplitude of startle reaction immediately after completion of the treatment. 9 days after drug withdrawal this effect was not observed. DEP in a dose of 1.0 mg/kg had no effect on the amplitude of startle reaction in any experiments described above. The above results demonstrate that MAO-A inhibitors--brofaromine and moclobemide and a MAO-B inhibitor--deprenyl show opposit activity in acoustic startle response test. BRO and MOC exert the inhibitory activity, whereas DEP has an excitatory effect on the startle reaction. The reference drug, AMI had no effect when given in a single doses (2 and 10 mg/kg, po). After repeated treatment (twice daily for 14 days, 2 or 10 mg/kg, po), AMI diminished the amplitude of the startle reaction only in higher dose when tested 2 h after the last dose and had no effect in the experiment carried out 5 days after the last dose.