The neurochemical and behavioral effects of the novel cholinesterase-monoamine oxidase inhibitor, ladostigil, in response to L-dopa and L-tryptophan, in rats

1 The novel drugs, ladostigil (TV3326) and TV3279, are R and S isomers, respectively, derived from a combination of the carbamate cholinesterase (ChE) inhibitor, rivastigmine, and the pharmacophore of the monoamine oxidase (MAO) B inhibitor, rasagiline. They were developed for the treatment of comorbidity of dementia with Parkinsonism. In the present study, we determined the effects of these drugs on both aminergic neurotransmitter levels and motor behavioral activity in naive and in L-dopa- or L-tryptophan-induced rats. 2 Chronic treatment of rats with ladostigil (52 mg kg(-1) for 21 days) inhibited hippocampal and striatal MAO A and B activities by > 90%, increased striatal levels of dopamine and serotonin, and inhibited striatal ChE activity by similar to 50%. 3 Chronic TV3279 (26 mg kg(-1) for 21 days) similarly inhibited similar to 50% of striatal ChE activity, but did not affect MAO activity or amine levels. 4 In sharp contrast to the inductive effect of the MAO A/B inhibitor, tranylcypromine (TCP), on stereotyped hyperactivity in response to L-dopa (50 mg kg(-1)) or L-tryptophan (100 mg kg(-1)), ladostigil completely inhibited these behavioral hyperactivity syndromes. Accordingly, acute rivastigmine (2 mg kg(-1)) and chronic TV3279 abolished the ability of TCP to initiate L-dopa-induced hyperactivity, while scopolamine (0.5 mg kg(-1)) reversed the inhibitory effect of chronic ladostigil on L-dopa-induced hyperactivity, suggesting that ladostigil may attenuate successive locomotion by activating central cholinergic muscarinic receptors. 5 Finally, while chronic ladostigil administration to naive rats resulted in preserved spontaneous motor behavior, acute treatment with ladostigil decreased motor performance, compared to control animals. In contrast, chronic as well as acute treatments with TV3279 reduced spontaneous motor activity. Thus, the aminergic potentiation by ladostigil may counteract its cholinergic inhibitory effect on spontaneous motor behavior. 6 Our results suggest that potentiation of both aminergic and cholinergic transmission systems by ladostigil contributes equally to motor behavior performance, which is substantially impaired in comorbidity of dementia with Parkinsonism including dementia with Lewy bodies (DLB).