Reboxetine mesylate

Reboxetine is a norepinephrine reuptake inhibitor with K_i of 8.2 nM.

Reboxetine modulates norepinephrine efflux in the frontal cortex of the freely moving rat: the involvement of alpha 2 and 5-HT1A receptors.[Pubmed:12932821]

Neurosci Lett. 2003 Sep 18;348(3):171-4.

The effect of reboxetine on norepinephrine (NE) efflux in the frontal cortex of freely moving rats has been studied using in vivo microdialysis. Reboxetine was administered either by injection (10 and 30 mg/kg i.p.) or directly to the frontal cortex via the dialysis probe (10 and 100 microM). To further elucidate the mechanism of action of reboxetine in this region yohimbine (10 microM) was co-infused with reboxetine via the frontal cortex probe. Both routes of administration of reboxetine resulted in a drug-induced, dose-dependent decrease in frontal cortex NE efflux. This effect was reversed following co-infusion of yohimbine, which has been shown to possess both alpha(2)-adrenoceptor antagonist and 5-HT(1A) agonist properties.

S33005, a novel ligand at both serotonin and norepinephrine transporters: I. Receptor binding, electrophysiological, and neurochemical profile in comparison with venlafaxine, reboxetine, citalopram, and clomipramine.[Pubmed:11454918]

J Pharmacol Exp Ther. 2001 Aug;298(2):565-80.

S33005 displayed marked affinity for native, rat, and cloned human serotonin (5-HT) transporters (SERT) and less pronounced affinity for norepinephrine (NE) transporters (NET), while its affinity at dopamine (DA) transporters and >50 other sites was negligible. Reuptake of 5-HT and (less potently) NE into cerebral synaptosomes was inhibited by S33005, whereas DA reuptake was little affected. In vivo, S33005 prevented depletion of cerebral pools of 5-HT by parachloroamphetamine. Furthermore, it decreased electrical activity of raphe-localized serotonergic neurones, an action abolished by the 5-HT1A antagonist WAY100,635. At higher doses, S33005 blocked firing of locus ceruleus-localized adrenergic neurones, an action abolished by the alpha2-adrenergic antagonist idazoxan. In contrast, S33005 did not inhibit ventrotegmental dopaminergic neurones. In frontal cortex of freely moving rats, S33005 dose dependently elevated dialysate levels of 5-HT, NE, and DA. In hippocampus, levels of 5-HT and NE were similarly elevated, while in nucleus accumbens and striatum, levels of 5-HT were increased whereas DA was unaffected. Upon chronic (2 weeks) administration, basal levels of NE were elevated in frontal cortex and, therein, 5-HT2A receptor density was decreased. Comparative studies with clinically used antidepressants showed that venlafaxine possessed a profile similar to S33005 but was less potent. Clomipramine likewise interacted with SERTs and NETs but also with several other receptors types, while citalopram and reboxetine were preferential ligands of SERTs and NETs, respectively. In conclusion, S33005 interacts potently with SERTs and, less markedly, with NETs. It enhances extracellular levels of 5-HT and NE throughout corticolimbic structures and selectively elevates dialysis levels of DA in frontal cortex versus subcortical regions.

Reboxetine: a pharmacologically potent, selective, and specific norepinephrine reuptake inhibitor.[Pubmed:10812041]

Biol Psychiatry. 2000 May 1;47(9):818-29.

BACKGROUND: Reboxetine is a potent antidepressant, with efficacy comparable to that of imipramine, desipramine, and fluoxetine, and has improved side-effect profile. The basis of its efficacy and improved tolerability is sought through studies of reboxetine in a number of pharmacological models of depression. METHODS: Pharmacological selectivity for uptake systems was defined by uptake and binding assays for the three monoamine uptake sites. Specificity was determined in 39 different receptor and 6 enzyme assays. In vivo selectivity was defined by measurement of neuronal firing rates in the locus coeruleus, dorsal raphe, and substantia nigra. Reserpine-induced blepharospasm and hypothermia, clonidine-induced hypothermia, defined reboxetine's in vivo pharmacology. Reboxetine's antidepressant potential was evaluated behaviorally by the tail-suspension test, forced swimming, and the DRL72 operant responding test. RESULTS: Reboxetine is a potent, selective, and specific norepinephrine reuptake inhibitor (selective NRI) as determined by both in vitro and in vivo measurements. Unlike desipramine or imipramine, reboxetine has weak affinity (Ki > 1,000 nmol/L)for muscarinic, histaminergic H1, adrenergic alpha1, and dopaminergic D2 receptors. In vivo action of reboxetine is entirely consistent with the pharmacological action of an antidepressant with preferential action at the norepinephrine reuptake site. Reboxetine showed an antidepressant profile in all tests of antidepressant activity used. Significant decreases in immobility were observed in the tail suspension test and behavioral despair test. Increased efficiency in responding was observed in the DRL72 test. CONCLUSIONS: Reboxetine is a potent, selective, and specific noradrenergic reuptake inhibitor. It has a superior pharmacological selectivity to existing tricyclic antidepressants and selective serotonin reuptake inhibitors when tested in a large number of in vitro and in vivo systems. Given the pharmacological profile, reboxetine is expected to be a selective and potent tool for psychopharmacological research. The use of reboxetine in the clinic will also help clarify the role norepinephrine plays in depression.

Studies on the acute and chronic effects of reboxetine on extracellular noradrenaline and other monoamines in the rat brain.[Pubmed:10578149]

Br J Pharmacol. 1999 Nov;128(6):1332-8.

1 The effect of reboxetine, a novel antidepressant drug that potently and selectively inhibits neuronal noradrenaline (NA) uptake, on brain extracellular monoamines was studied by microdialysis. 2 Fifteen mg kg-1 i.p. reboxetine raised extracellular NA in the frontal cortex (by 242%) and dorsal hippocampus (by 240%). 3 Idazoxan (1 mg kg-1 s.c.), given 60 min after 15 mg kg-1 reboxetine, markedly potentiated the effect on extracellular NA in the frontal cortex (by 1580%) and dorsal hippocampus (by 1360%), but had no effect by itself. 4 Twenty-four hours after the last injection of a chronic schedule (15 mg kg-1 i.p. once daily for 14 days) reboxetine had no effect on basal extracellular concentrations of NA in the dorsal hippocampus and a challenge dose of reboxetine (15 mg kg-1) raised extracellular NA similarly in rats treated chronically with reboxetine (by 353%) and saline (by 425%). 5 Ten and 20 microg kg-1 i.p. clonidine dose-dependently reduced hippocampal extracellular NA similarly in rats given chronic reboxetine (by 32% and 57%) and saline (by 42% and 56%). 6 Extracellular concentrations of dopamine and 5-HT in the striatum were similar in rats treated chronically with reboxetine and saline. A challenge dose of reboxetine (15 mg kg-1) had no effect on striatal extracellular dopamine and slightly increased striatal extracellular 5-HT to a similar extent in rats treated chronically with reboxetine (by 137%) and saline (by 142%). 7 The results suggest that combining reboxetine with an alpha2-adrenoceptor antagonist may facilitate its antidepressant activity. Repeated treatment confirmed that reboxetine is fairly selective for the noradrenergic system but provided no evidence of adaptive changes in that system that could facilitate its effect on extracellular NA.