Behavioral, biochemical and neurotoxicological actions of the α-ethyl homologue of p-chloroamphetamine

Abstract

The present set of experiments was designed to examine the effects of extension of the α-methyl of p-chloro-amphetamine (PCA) to an α-ethyl. Therefore, the α-ethyl homologue of PCA. l-(4-chlorophenyl)-2-aminobutane (CAB), was compared to PCA in a number of pharmacological assays. CAB was 2-fold less potent than PCA at inhibiting synaptosomal uptake of [ 3H]5-hydroxytryptamine ([ 3H]5-HT), and 5-fold less potent at inhibiting uptake of [ 3H]dopamine ([ 3H]DA). In drug discrimination assays, CAB was approximately 3-fold less potent than PCA in animals trained to discriminate 3,4-methylenedioxymethamphetamine (MDMA) or its α-ethyl homologue, S-(+)-N-methyl-1-(l,3-benzodioxol-5-yl)-2-butanamine (S-(+)-MBDB), from saline. Monitoring with in vivo microdialysis, 10 mg/kg of PCA caused a large increase in extracellular DA and a significant decrease in 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum. In contrast, 11 mg/kg CAB caused no increase and 22 mg/kg CAB caused only a slight increase in extracellular DA. Both doses of CAB caused a decrease in extracellular DOPAC. The potential 5-HT neurotoxicity of CAB was examined by measuring monoamine and metabolite levels and [ 3H]paroxetine binding at one week following acute doses. A 10 mg/kg dose of PCA caused an 80% decrease in cortical and hippocampal serotonergic markers, while an equimolar dose of CAB decreased only hippocampal 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) levels. However, 22 mg/kg of CAB produced a 20–40% decrease in all serotonergic markers. Thus, extension of the α-alkyl significantly decreases the dopaminergic effects of PCA. The similar decrease in relative 5-HT neurotoxicity and the decreased ability to alter dopaminergic systems in vivo and in vitro supports the involvement of DA in the neurotoxicity of PCA.