No abstract

The purpose of this study was to characterize a new chemical entity, desvenlafaxine succinate (DVS). DVS is a novel salt form of the isolated major active metabolite of venlafaxine. Competitive radioligand binding assays were performed using cells expressing either the human serotonin (5-HT) transporter (hSERT) or norepinephrine (NE) transporter (hNET) with K i values for DVS of 40.2 Ϯ 1.6 and 558.4 Ϯ 121.6 nM, respectively. DVS showed weak binding affinity (62% inhibition at 100 M) at the human dopamine (DA) transporter. Inhibition of , examined at a large number of nontransporter targets, showed no significant activity. DVS (30 mg/kg orally) rapidly penetrated the male rat brain and hypothalamus. DVS (30 mg/kg orally) significantly increased extracellular NE levels compared with baseline in the male rat hypothalamus but had no effect on DA levels using microdialysis. To mimic chronic selective serotonin reuptake inhibitor treatment and to block the inhibitory 5-HT 1A autoreceptors, a 5-hexanecarboxamide maleate salt (WAY-100635) (0.3 mg/kg s.c.), was administered with DVS (30 mg/kg orally). 5-HT increased 78% compared with baseline with no additional increase in NE or DA levels. In conclusion, DVS is a new 5-HT and NE reuptake inhibitor in vitro and in vivo that demonstrates good brain-to-plasma ratios, suggesting utility in a variety of central nervous system-related disorders.Biogenic amines such as serotonin (5-HT), norepinephrine (NE), and dopamine (DA) are neurotransmitters found in areas of the central nervous system (CNS) known to be important for regulation of cognitive function, mood, thermoregulation, pain sensation, sexual function, and various aspects of endocrine function related to homeostasis. Their synthesis is highly regulated, and long-term disturbance of the regulatory pathways for these neurotransmitters may lead to disruptions in overall health and quality of life. As with any specific mechanism that controls a physiological process, regulation of these neurotransmitters is a target of many pharmacological agents. Agents that have been developed to modulate these key neurotransmitters are well characterized and have provided evidence that regulation of these neurotransmitters affects physiological outcomes specific to each neurotransmitter. There are multiple means of regulating these neurotransmitters. One means is by inhibiting their presynaptic reuptake. Monoamine reuptake inhibitors work by binding to their respective transporter proteins located presynaptically. This binding interaction results in an increase in elimination time of the neurotransmitter cycle; thus, the extracellular concentration of the neurotransmitters increases in the synaptic cleft. This increase in neurotransmitter in the cleft allows for increased downstream cellular signaling (Blakely and Bauman, 2000). Serotonin and norepinephrine reuptake inhibitors (SNRIs) work by blocking the presynaptic reuptake of 5-HT and NE, resulting in an increased sustained level of both of these neurotransmitters. The 5-HT a...

Muth, E.A., J.A. Moyer, J.T. Haskins, T.H. Andree, and G.E. M. Husbands:Biochemical, neurophysiological, and behavioral effects of Wy-45,233 and other identified metabolites of the antidepressant venlafaxine. Drug Dev. Res. 23:191-199, 1991. Seven metabolites of venlafaxine, identified in several species, were examined for CNS pharmacological activity in rodents. The 0-desmethyl compound Wy-45,233, which is the major metabolite in man, had the greatest preclinical activity. This metabolite exhibited an antidepressant profile (monoamine uptake blockade, reversal of reserpine hypothermia, induction of pineal p-adrenergic subsensitivity) comparable to the parent drug, venlafaxine. This compound also inhibited serotonergic and noradrenergic firing rates like the parent compound, but with less potency. The cyclohexyl ring-hydroxylated metabolite 877 and the N-desmethyl metabolite Wy-45,494 were also active in reserpine hypothermia, but Wy-45,494 was a weaker inhibitor of serotonin uptake and both metabolites were weaker inhibitors of norepinephrine uptake than Wy-45,233. None of the seven metabolites tested exhibited significated binding at dopamine-2, muscarinic cholinergic, a-1 -adrenergic, histamine-1 , or opiate (k) receptors. These results suggest that Wy-45,233, the 0-desmethyl metabolite of venlafaxine, is an active metabolite which retains the benign side-effect profile of venlafaxine.

A series of 2-phenyl-2-(1-hydroxycycloalkyl)ethylamine derivatives was examined for the ability to inhibit both rat brain imipramine receptor binding and the synaptosomal uptake of norepinephrine (NE) and serotonin (5-HT). Neurotransmitter uptake inhibition was highest for a subset of 2-phenyl-2-(1-hydroxycyclohexyl)dimethylethylamines in which the aryl ring has a halogen or methoxy substituent at the 3- and/or 4-positions. Potential antidepressant activity in this subset was assayed in three rodent models--the antagonism of reserpine-induced hypothermia, the antagonism of histamine-induced ACTH release, and the ability to reduce noradrenergic responsiveness in the rat pineal gland. An acute effect seen in the rat pineal gland with several analogues, including 1-[1-(3,4-dichlorophenyl)-2-(dimethylamino)ethyl]cyclohexanol (23) and 1-[2-(dimethylamino)-1)-(4-methoxyphenyl)ethyl]cyclohexanol (4), was taken as a possible correlate of a rapid onset of antidepressant activity. Compound 4 (venlafaxine) is presently undergoing clinical evaluation.

There is increasing recognition that norepinephrine (NE) and serotonin (5-HT) reuptake inhibitors (NRIs and SRIs) are efficacious in treating some types of pain. To date, studies have not systematically evaluated the relative activity at the NE and/or 5-HT transporter required for maximal efficacy in rodent pain models. Known selective NE and 5-HT reuptake inhibitors reboxetine, desipramine, fluoxetine, and paroxetine were evaluated in both in vitro and in vivo assays. Using the spinal nerve ligation model of neuropathic pain, the compounds differentially reversed tactile allodynia. Evaluation of a broader spectrum of reuptake inhibitors in the para-phenylquinone (PPQ)-induced abdominal constriction model, a model of acute visceral pain, demonstrated that both the SRIs and the NRIs significantly blocked abdominal constrictions. However, the magnitude of this effect was greater following treatment with compounds having greater affinity for NRI compared with SRI affinity. In addition, isobolographic analyses indicated significant synergistic effects for all combinations of desipramine and fluoxetine in the PPQ model of visceral pain. Collectively, the present results support the hypothesis that compounds with greater NRI activity should be more effective for the treatment of pain than compounds having only SRI activity, and this hypothesis is also supported by clinical data. These studies also suggest that the potency and effectiveness of NRIs might be enhanced by the presence of 5-HT activity.

A series of 2-(aminomethyl)chromans (2-AMCs) was synthesized and evaluated for their affinity and selectivity for both the high- and low-affinity agonist states (D2High and D2Low, respectively) of the dopamine (DA) D2 receptor. The 7-hydroxy-2-(aminomethyl)chroman moiety was observed to be the primary D2 agonist pharmacophore. The 2-methylchroman moiety was discovered to be an entirely novel scaffold which could be used to access the D2 agonist pharmacophore. Attaching various simple alkyl and arylalkyl side chains to the 7-hydroxy 2-AMC nucleus had significant effects on selectivity for the D2High receptor vs the 5HT1A and alpha 1 receptors. A novel DA partial agonist, (R)-(-)-2-(benzylamino)methyl)chroman-7-ol [R-(-)-35c], was identified as having the highest affinity and best selectivity for the D2High receptor vs the alpha 1 and 5HT1A receptors. Several regions of the 2-AMC nucleus were modified and recognized as potential sites to modulate the level of intrinsic activity. The global minimum conformer of the 7-hydroxy-2-AMC moiety was identified as fulfilling the McDermed model D2 agonist pharmacophoric criteria and was proposed as the D2 receptor-bound conformation. Structure-activity relationships gained from these studies have aided in the synthesis of D2 partial agonists of varying intrinsic activity levels. These agents should be of therapeutic value in treating disorders resulting from hypo- and hyperdopaminergic activity, without the side effects associated with complete D2 agonism or antagonism.

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Several novel substituted gamma-carbolines were synthesized and examined in a series of in vitro and in vivo pharmacological tests to determine potential antipsychotic activity. Most compounds were orally active in blocking the conditioned avoidance response (CAR) in rats but did not antagonize apomorphine-induced stereotyped behavior. Compound 17 (Wy-47,384), a gamma-carboline with a 3-(3-pyridinyl)propyl side chain, was selected for development as an atypical antipsychotic agent because of its potent and selective profile in preclinical psychopharmacological tests. It blocked CAR in rats with an AB50 of 14 mg/kg po, showed weak affinity for the D2 receptor site (Ki = 104 nM), and showed differential potency in antagonizing apomorphine-induced stereotyped behavior (ED50 = 11 mg/kg ip) and climbing behavior (ED50 = 4 mg/kg ip). Such activities are suggestive of antipsychotic efficacy combined with a low potential for extrapyramidal side effect (EPS) liability.