Re-evaluation of the discriminative stimulus effects of lysergic acid diethylamide with male and female Sprague-Dawley rats
BEHAVIOURAL PHARMACOLOGY
Authors: Herr, Keli A.; Baker, Lisa E.
Abstract
Recent discoveries from clinical trials with psychedelic-assisted therapy have led to a resurgence of interest in the psychopharmacology of lysergic acid diethylamide (LSD). Preclinical drug discrimination is an invaluable tool to investigate the neurochemical mechanisms underlying subjective drug effects. The current study extends previous drug discrimination research by including both sexes. Adult female (n = 8) and male (n = 8) Sprague-Dawley rats were trained to discriminate 0.08 mg/kg LSD from saline under a fixed ratio 20 schedule of food reinforcement. Substitution tests were conducted with several substances, including other serotonergic hallucinogens, psychostimulants, mixed psychedelic-stimulants and synthetic cathinones. Stimulus antagonist tests were conducted with selected serotonin and dopamine antagonists. LSD-substitution with serotonergic hallucinogens was comparable between sexes. Modest but intriguing differences were observed between male and female rats in the extent of partial substitution by 3,4-methylenedioxymethamphetamine and 3,4-methylenedioxyamphetamine enantiomers and the synthetic cathinones, 3,4-methylenedioxypyrovalerone and 4-methylmethcathinone. Dopamine antagonists failed to block the LSD cue in both sexes and exerted stronger rate suppressant effects in male rats. The 5-hydroxytryptamine antagonist, (R)-(+)-a-(2,3-dimethoxyphenyl)-1-[2-(4-fluorophenyl) ethyl]-4-piperidinemethanol (MDL 100 907) blocked LSD discrimination in both sexes, although complete blockade was evident at lower doses in male rats. These results support previous findings regarding the prominent role of serotonergic activities underlying LSDs discriminative stimulus effects in male rats and generalize these findings to female rats. In consideration of the rising popularity in psychedelic-assisted psychotherapy, further research may be warranted to evaluate possible sex differences in the behavioral and subjective effects of LSD.
Mechanism of atmospheric pressure chemical ionization of morphine, codeine, and thebaine in corona discharge-ion mobility spectrometry: Protonation, ammonium attachment, and carbocation formation
JOURNAL OF MASS SPECTROMETRY
Authors: Valadbeigi, Younes; Ilbeigi, Vahideh; Mirsharifi, Maryam S.
Abstract
Atmospheric pressure chemical ionizations (APCIs) of morphine, codeine, and thebaine were studied in a corona discharge ion source using ion mobility spectrometry (IMS) at temperature range of 100 degrees C-200 degrees C. Density functional theory (DFT) at the B3LYP/6-311++G(d,p) and M062X/6-311++G(d,p) levels of theory were used to interpret the experimental data. It was found that in the presence of H(3)O(+)as reactant ion (RI), ionization of morphine and codeine proceeds via both the protonation and carbocation formation, whereas thebaine participates only in protonation. Carbocation formation (fragmentation) was diminished with decrease in the temperature. At lower temperatures, proton-bound dimers of the compounds were also formed. Ammonia was used as a dopant to produce NH(4)(+)as an alternative RI. In the presence of NH4+, proton transfer from ammonium ion to morphine, codeine, and thebaine was the dominant mechanism of ionization. However, small amount of ammonium attachment was also observed. The theoretical calculations showed that nitrogen atom of the molecules is the most favorable proton acceptor site while the oxygen atoms participate in ammonium attachment. Furthermore, formation of the carbocations is because of the water elimination from the protonated forms of morphine and codeine.