Marie-Claire Rettori

Preclinical profile of the mixed 5-HT1A/5-HT2A receptor antagonist S 21357

This study evaluated the pharmacological and behavioral effects of S 21,357, a drug with high affinity for both 5-HT1A and 5-HT2A receptors. The drug behaved as antagonist at both 5-HT1A autoreceptors and postsynaptic 5-HT1A receptors, as it prevented the inhibitory effect of lesopitron on the electrical discharge of the dorsal raphé nucleus (DRN) 5-HT neurons and the activity of forskolin-stimulated adenylate cyclase in hippocampal homogenates. In addition, S 21,357 (4 and 128 mg/kg, PO) inhibited 5-HTP-induced head-twitch responses in mice, indicating that it possesses 5-HT2A antagonistic properties. In a test battery designed to assess defensive behaviors of Swiss-Webster mice to the presence of, or situations associated with, a natural threat stimulus (i.e., rat), S 21,357 (0.12-2 mg/kg, IP) reduced contextual defense reactions after the rat was removed, risk assessment activities when the subject was chased, and finally, defensive attack behavior. These behavioral changes are consistent with fear/anxiety reduction. Furthermore, the drug strongly reduced flight reactions in response to the approaching rat. This last finding, taken together with recent results with panic-modulating drugs, suggest that S 21,357 may have potential efficacy against panic attack. Finally, our results suggest that compounds sharing high affinities for both 5-HT1A and 5-HT2A receptors may directly or synergistically increase the range of defensive behaviors affected.

Synthesis and structure-activity relationships of novel 2-amino alkyl chromones and related derivatives as a site-selective ligands

Abstract Starting from a random screening showing that 2-[(4-benzylpiperazinyl)methyl] chromone was a selective and potent sigma ligand, a series of analogues were synthesized. Introduction of a substituent on the chromone moiety, replacement of methy-lenes by carbonyl groups and benzyl by aryl groups decrease the affinity for sigma sites. The result obtained after introduction of various substituents on the aromatic part of the benzyl is strictly depending on the size and on the position of these substituents. Stretching of the carbon chain between the phenyl and the piperazine does not strongly modify the affinity. 2-[4-(4′-methoxy benzyl)-1-piperazinyl methyl] chromone has been tested in behavioral tests that permit to believe that such derivatives could be interesting for the treatment of psychosis.

Interactions between imidazoline binding sites and dopamine levels in the rat nucleus accumbens

Imidazoline binding sites are present in the striatal complex and in the extended amygdala and have been implicated in mood disorders. In this report we analysed the influence of these sites on the functional activity of the mesolimbic dopaminergic transmission, one of the major brain systems involved in the regulation of motivation and reward. We studied the effects of two imidazoline ligands, S23229 and S23230 (respectively S(+) and R(–) enantiomers of the S22687 or (5‐[2‐methyl phenoxy methyl] 1,3‐oxazolin‐2‐yl) amine), on extracellular dopamine in the nucleus accumbens using microdialysis in freely moving rats. We compared these imidazoline ligands to cocaine, a dopamine uptake blocker known to increase extracellular dopamine concentrations. S23229 dose‐dependently increased extracellular dopamine and locomotor activity. S23230 dose‐dependently increased extracellular dopamine and produced a near‐significant dose–effect on locomotor activity. S23229 had a stronger efficacy than S23230 and increased dopamine levels in the nucleus accumbens at an extent similar to the one of cocaine. These results suggest that central imidazoline binding sites could contribute to the functional regulation of the mesolimbic dopaminergic system.

N,N-Disubstituted Aminomethyl Benzofuran Derivatives: Synthesis and Preliminary Binding Evaluation

A series of new N-substituted 2,3-dihydro-2-aminomethyl-2H-1-benzofuran derivatives was prepared and evaluated for affinity at 5-HT1A, 5-HT2A, 5-HT2C, 5-HT3, D2, and D3 receptors. Compound 9, 8-[4-[N-propyl-N-(7-hydroxy-2,3-dihydro -2H-1-benzofuran-2-yl)methyl]aminobutyl]-8-azaspiro[4,5]decane-7,9 -dione, bound at 5-HT1A sites with nanomolar affinity (IC50= 1.5 nM) and high selectivity over 5-HT2A, 5-HT2C, 5-HT3, D2, and D3 receptors.

Melatonin MT1/2 receptor stimulation reduces cortical overflow of cholecystokinin-like material in a model of anticipation of social defeat in the rat

The involvement of cholecystokinin (CCK) in the potential anxiolytic-like effects of melatonin and of the antitumor MT(1/2) receptor agonist, S23478, was assessed by measuring the cortical outflow of CCK-like material (CCKLM) in a rat model of anticipation of social defeat. After repeated social defeats by a male Tryon Maze Dull (TMD) rat, Sprague-Dawley (SD) rats were implanted for microdialysis in the frontal cortex and placed in the same environment as for the defeated sessions, but no confrontation with the TMD rat was allowed. Anticipation of social defeat induced anxiety-like behaviors (immobility, ultrasonic vocalization, defensive postures) associated with a significant increase (approximately +90%) in cortical CCKLM outflow in SD rats. Acute pretreatment with melatonin (5 or 40 mg/kg i.p.) or S23478, at 5 mg/kg i.p., had no or only minor effects on anxiety-like behaviors and did not affect CCKLM overflow. In contrast, at 40 mg/kg i.p., S23478 significantly reduced the duration of immobility and vocalization as well as the cortical CCKLM overflow (-30%) in defeated SD rats, and both effects were prevented by the MT(1/2) receptor antagonist S22153 (40 mg/kg i.p.). These data indicated that MT(1/2) receptor stimulation can exert anxiolytic-like effects associated with inhibition of cortical CCKergic neurotransmission in rats anticipating social defeat.The involvement of cholecystokinin (CCK) in the potential anxiolytic-like effects of melatonin and of the antitumor MT1/2 receptor agonist, S23478, was assessed by measuring the cortical outflow of CCK-like material (CCKLM) in a rat model of anticipation of social defeat. After repeated social defeats by a male Tryon Maze Dull (TMD) rat, Sprague-Dawley (SD) rats were implanted for microdialysis in the frontal cortex and placed in the same environment as for the defeated sessions, but no confrontation with the TMD rat was allowed. Anticipation of social defeat induced anxiety-like behaviors (immobility, ultrasonic vocalization, defensive postures) associated with a significant increase (~+90%) in cortical CCKLM outflow in SD rats. Acute pretreatment with melatonin (5 or 40 mg/kg i.p.) or S23478, at 5 mg/kg i.p., had no or only minor effects on anxiety-like behaviors and did not affect CCKLM overflow. In contrast, at 40 mg/kg i.p., S23478 significantly reduced the duration of immobility and vocalization as well as the cortical CCKLM overflow (-30%) in defeated SD rats, and both effects were prevented by the MT1/2 receptor antagonist S22153 (40 mg/kg i.p.). These data indicated that MT1/2 receptor stimulation can exert anxiolytic-like effects associated with inhibition of cortical CCKergic neurotransmission in rats anticipating social defeat.

5-HT1A and 5-HT2A ligands with anxiolytic and antipanic-like properties

Abstract A series of new benzothiazolin-2-one, benzoxazolin-2-one and benzoxazin-3-one derivatives were synthesized and their binding profile at 5-HT1A, 5-HT2A, 5-HT2C as well as D2 and α1 receptors was determined. All studied compounds displayed high to moderate affinity for both 5-HT1A and 5-HT2A receptor subtypes. Among these, one compound (29) emerged since it exhibited potent antagonist activities at 5-HT1A, 5-HT2A, D2 and α1 central receptors and showed anxiolytic and antipanic-like effects in mice. 29 is currently undergoing preclinical evaluation.

Derivatization of (′)-5-[(2-methylphenoxy)methyl]-2-amino-2-oxazoline, an imidazoline binding sites ligand, with (+)-(R)-α-methylbenzyl isocyanate for drug monitoring purposes

The derivatization of racemic 5-[(2-methylphenoxy)methyl]-2-amino-2-oxazoline, developed as an imidazoline binding sites ligand, with (+)- (R) - α -methylbenzyl isocyanate was performed in chloroform. The reaction led to two pairs of diastereomers, which were separated by RP-HPLC. A kinetic study of the derivatization reaction was achieved in order to establish conditions suitable for experimental drug monitoring.