In Vitro Characterization of Ephedrine-Related Stereoisomers at Biogenic Amine Transporters and the Receptorome Reveals Selective Actions as Norepinephrine Transporter Substrates

Abstract

Ephedrine is a long-studied stimulant available both as a prescription and over-the-counter medication, as well as an ingredient in widely marketed herbal preparations, and is also used as a precursor for the illicit synthesis of methamphetamine. Ephedrine is related to phenylpropanolamine, a decongestant removed from the market place due to concerns that its use increased the risk of hemorrhagic stroke. Standard pharmacology texts emphasize that ephedrine is both a direct and indirect adrenergic agonist, activating adrenergic receptors both by direct agonist activity as well as by releasing norepinephrine via a carrier-mediated exchange mechanism. Chemically, ephedrine possesses two chiral centers. In the present study, we characterized the stereoisomers of ephedrine and the closely related compounds pseudoephedrine, norephedrine, pseudonorephedrine (cathine), methcathinone, and cathinone at biogenic amine transporters and a large battery of cloned human receptors (e.g., "receptorome"). The most potent actions of ephedrine-type compounds were as substrates of the norepinephrine transporter (EC 50 values of about 50 nM) followed by substrate activity at the dopamine transporter. Screening the receptorome demonstrated weak affinity at ␣ 2 -adrenergic and 5-hydroxytryptamine 7 receptors (K i values 1-10 M) and no significant activity at ␤-adrenergic or ␣ 1 -adrenergic receptors. Viewed collectively, these data indicate that the pharmacological effects of ephedrine-like phenylpropanolamines are likely mediated by norepinephrine release, and although sharing mechanistic similarities with, they differ in important respects from those of the phenylpropanonamines methcathinone and cathinone and the phenyisopropylamines methamphetamine and amphetamine.

Pharmacologic analysis of non-synonymous coding h5-HT2A SNPs reveals alterations in atypical antipsychotic and agonist efficacies

“…After an overnight serum depriva-tion, intracellular calcium flux assays were performed using a Molecular Devices Calcium Plus Assay kit and a FLEX Station II fluorescence plate reader (Molecular Devices). 46,47 with a few modifications. Briefly, cells were washed once with 100 ml serum-free, indicator-free DMEM.…”

Khat (Catha edulis)-induced apoptosis is inhibited by antagonists of caspase-1 and -8 in human leukaemia cells

“…Other alkaloid compounds such as the phenylpentenylamines and cathedulines could also contribute to pharmacological effects of khat (Kalix, 1992;Al-Motarreb et al, 2002). Most of their pharmacological effects are suggested as being mediated by release of biogenic amines through preferential binding to the norepinephrine receptor/transporter, but also partly through binding to dopamine and 5-hydroxytryptamine receptors (Rothman et al, 2003).…”

Therapeutic Potential of Monoamine Transporter Substrates

“…The data in Fig. 3 [43]. The collective findings illustrate that our assay systems can readily discriminate releasers from uptake blockers.…”

“…This work served to identify the mechanism of action of known stimulant-type agents [40][41][42][43] and to guide the synthesis and evaluation of novel treatment agents for addictive disorders [21]. Traditionally, it has been difficult to use simple test tube assays to discriminate between drugs that are uptake inhibitors vs. those that are substrate-type releasers [8,11].…”

“…From [43]. a All agents behaved as substrates except for (-)-pseudoephedrine which displayed activity in the DA uptake assay.…”