Effects of some rigid analogues of imipramine and amitriptyline on the uptake of noradrenaline, serotonin and choline in rat brain synaptosomes

Quinolizidine-Derived Lucanthone and Amitriptyline Analogues Endowed with Potent Antileishmanial Activity

Leishmaniases are neglected diseases that are endemic in many tropical and sub-tropical Countries. Therapy is based on different classes of drugs which are burdened by severe side effects, occurrence of resistance and high costs, thereby creating the need for more efficacious, safer and inexpensive drugs. Herein, sixteen 9-thioxanthenone derivatives (lucanthone analogues) and four compounds embodying the diarylethene substructure of amitriptyline (amitriptyline analogues) were tested in vitro for activity against Leishmania tropica and L. infantum promastigotes. All compounds were characterized by the presence of a bulky quinolizidinylalkyl moiety. All compounds displayed activity against both species of Leishmania with IC₅₀ values in the low micromolar range, resulting in several fold more potency than miltefosine, comparable to that of lucanthone, and endowed with substantially lower cytotoxicity to Vero-76 cells, for the best of them. Thus, 4-amino-1-(quinolizidinylethyl)aminothioxanthen-9-one (14) and 9-(quinolizidinylmethylidene)fluorene (17), with selectivity index (SI) in the range 16-24, represent promising leads for the development of improved antileishmanial agents. These two compounds also exhibited comparable activity against intramacrophagic amastigotes of L. infantum. Docking studies have suggested that the inhibition of trypanothione reductase (TryR) may be at the basis (eventually besides other mechanisms) of the observed antileishmanial activity. Therefore, these investigated derivatives may deserve further structural improvements and more in-depth biological studies of their mechanisms of action in order to develop more efficient antiparasitic agents.

Chronic effects of antidepressants on serotonin release in rat raphe slice cultures: high potency of milnacipran in the augmentation of serotonin release

Most clinically-used antidepressants acutely increase monoamine levels in synaptic clefts, while their therapeutic effects often require several weeks of administration. Slow neuroadaptive changes in serotonergic neurons are considered to underlie this delayed onset of beneficial actions. Recently, we reported that sustained exposure of rat organotypic raphe slice cultures containing abundant serotonergic neurons to selective serotonin (5-HT) reuptake inhibitors (citalopram, fluoxetine and paroxetine) caused the augmentation of exocytotic serotonin release. However, the ability of other classes of antidepressants to evoke a similar outcome has not been clarified. In this study, we investigated the sustained actions of two tricyclic antidepressants (imipramine and desipramine), one tetracyclic antidepressant (mianserin), three 5-HT and noradrenaline reuptake inhibitors (milnacipran, duloxetine and venlafaxine) and one noradrenergic and specific serotonergic antidepressant (mirtazapine) on serotonin release in the slice cultures. For seven of nine antidepressants, sustained exposure to the agents at concentrations of 0.1-100 μ m augmented the level of increase in extracellular serotonin. The rank order of their potency was as follows: milnacipran>duloxetine>citalopram>venlafaxine>imipramine>fluoxetine>desipramine. Neither mirtazapine nor mianserin caused any augmentation. The highest augmentation by sustained exposure to milnacipran was partially attenuated by an α 1-adrenoceptor antagonist, benoxathian, while the duloxetine-, venlafaxine- and citalopram-mediated increases were not affected. These results suggest that inhibition of the 5-HT transporter is required for the enhancement of serotonin release. Furthermore, the potent augmentation by milnacipran is apparently due to the accompanied activation of the α 1-adrenoceptor.