Abstract
The pattern of activation of dopamine (DA) neurotransmission in the nucleus accumbens (NAc) of rats produced by H(1) histamine antagonists which have behavioral effects like those of psychostimulant drugs was examined. Diphenhydramine and (+)-chlorpheniramine were compared with triprolidine, a potent and selective H(1) antagonist and (-)-chlorpheniramine which is less active than its enantiomer at H(1) receptors. Affinities of the drugs to DA, serotonin, and norepinephrine transporters at H(1) receptors and potencies for DA uptake inhibition in striatal synaptosomes were determined to assess mechanisms by which the compounds increased DA levels. Intravenous diphenhydramine (1.0-3.0 mg/kg) (+)- and (-)-chlorpheniramine (1.0-5.6 mg/kg) but not triprolidine (1.0-3.0 mg/kg) elicited a cocaine-like pattern of stimulation of DA transmission with larger effects in the NAc shell than core. The absence of stereospecific effects with chlorpheniramine enantiomers along with the lack of an effect with triprolidine suggest that the effects on DA transmission were not related to H(1) receptor antagonism. Although in vivo potencies were not directly related to DA transporter affinities, it is hypothesized that actions at that site modulated by other actions, possibly those at the serotonin transporter, are primarily responsible for the neurochemical actions of the drugs on DA neurotransmission and might underlie the occasional misuse of these medications.
Publication types
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Research Support, N.I.H., Intramural
MeSH terms
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Animals
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Central Nervous System Stimulants / adverse effects
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Central Nervous System Stimulants / pharmacology*
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Chlorpheniramine / adverse effects
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Chlorpheniramine / pharmacology
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Cocaine / agonists*
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Diphenhydramine / adverse effects
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Diphenhydramine / pharmacology
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Dopamine / metabolism*
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Dopamine Agonists / adverse effects
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Dopamine Agonists / pharmacology*
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Dopamine Plasma Membrane Transport Proteins / drug effects
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Dopamine Plasma Membrane Transport Proteins / metabolism
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Dopamine Uptake Inhibitors / agonists
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Histamine H1 Antagonists / adverse effects
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Histamine H1 Antagonists / pharmacology*
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Male
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Nucleus Accumbens / drug effects*
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Nucleus Accumbens / metabolism
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Presynaptic Terminals / drug effects
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Presynaptic Terminals / metabolism
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Rats
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Rats, Sprague-Dawley
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Reward
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Serotonin Plasma Membrane Transport Proteins / drug effects
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Serotonin Plasma Membrane Transport Proteins / metabolism
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Stereoisomerism
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Substance-Related Disorders / metabolism
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Substance-Related Disorders / physiopathology
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Synaptic Transmission / drug effects
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Synaptic Transmission / physiology
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Synaptosomes / drug effects
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Synaptosomes / metabolism
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Triprolidine / adverse effects
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Triprolidine / pharmacology
Substances
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Central Nervous System Stimulants
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Dopamine Agonists
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Dopamine Plasma Membrane Transport Proteins
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Dopamine Uptake Inhibitors
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Histamine H1 Antagonists
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Serotonin Plasma Membrane Transport Proteins
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Triprolidine
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Chlorpheniramine
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Diphenhydramine
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Cocaine
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Dopamine