Abstract
The dopaminergic system plays a central role in the processing of reward or reinforcement since drugs that have reinforcing properties all share the ability to elevate dopamine (DA) levels in the nucleus accumbens or neostriatum. Histamine H1 receptor antagonists are known to have reinforcing effects in humans and laboratory rats. Here, we examined the effect of systemic (i.p.) <a href="http://www.springerl...0lt8xvnvhlt6/#" id="_GPLITA_1" in_rurl="http://i.trkjmp.com/...NDA3MDNkZmRmYw" style="margin: 0px; padding: 0px; border: 0px; outline: 0px; vertical-align: baseline; background-color: transparent;" title="Click to Continue > by Coupon Companion">treatment with two H1 antagonists, chlorpheniramine and pyrilamine, on the extracellular levels of DA and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the neostriatum and nucleus accumbens of urethane-anesthetized rats. Dopamine and metabolites were measured using in vivo microdialysis and HPLC with electrochemical detection. Saline injections did not produce significant effects on DA, DOPAC, or HVA levels in the neostriatum or nucleus accumbens. In the neostriatum, chlorpheniramine administration (5 and 20 mg/kg) produced a sustained increase in DA to approximately 140 and 180% of pre-injection baseline levels, respectively. In the nucleus accumbens, chlorpheniramine (20 mg/kg) produced a transient increase in DA levels to about 300% of baseline. In both the neostriatum and nucleus accumbens, DOPAC and HVA decreased after chlorpheniramine treatment. Pyrilamine administration (10 and 20 mg/kg) produced a sustained increase in neostriatal DA levels to 140 and 165%, respectively, and accumbens DA increased transiently to 230% after a dose of 20 mg/kg. Levels of neostriatal and accumbens DOPAC and HVA decreased after pyrilamine treatment. These results show that H1 antagonists can potently enhance DA levels in the neostriatum and nucleus accumbens of urethane-anesthetized rats. The neurochemical effects on DA and its metabolites seen here (increased DA, decreased DOPAC and HVA) are similar to those commonly observed with drugs of abuse (e.g. psychostimulants). The interaction of H1 antagonists with dopaminergic transmission may explain the reinforcing effects and abuse potential associated with these compounds.
Cocaine-like neurochemical effects of antihistaminic medications.
Tanda G, Kopajtic TA, Katz JL.
Source
Psychobiology Section, Medications Discovery Research Branch, Department of Health and Human Services, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland 21224, USA. gtanda@intra.nida.nih.gov
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.
Diphenylpyraline, a histamine H1 receptor antagonist, has psychostimulant properties.
Lapa GB, Mathews TA, Harp J, Budygin EA, Jones SR.
Source
Department of Physiology and Pharmacology, Wake Forest University Health Sciences, Winston-Salem, NC 27157, USA.
Abstract
Diphenylpyraline hydrochloride (DPP) is used clinically as an antihistamine drug, but its neurobiological effects are not completely understood. Voltammetry and microdialysis were used to investigate potential actions of DPP on the dopamine system. Voltammetric monitoring of dopamine signals in mouse nucleus accumbens slices showed that DPP (10 microM) markedly inhibited dopamine uptake. There was a 20-fold increase in apparent Km for dopamine uptake, while Vmax was unchanged. Microdialysis experiments demonstrated that DPP (5 mg/kg, i.p.) elevated extracellular dopamine levels (approximately 200%) in mouse nucleus accumbens. DPP (5 and 10 mg/kg) also induced locomotor activation. All of the effects of DPP were comparable with those of cocaine. Taken together, these results indicate that DPP acts as a competitive dopamine transporter inhibitor similar to cocaine.
Remember guys da does
not cause euphoria nor will antihistamines.
