title: Circadian variation in the head twitch response produced by 5-methoxy-N1,N1-dimethyltryptamine and p-chloroamphetamine in the mouse.
abstract: Circadian fluctuations were measured in the head twitch response produced by 5-methoxy-N1,N1-dimethyltryptamine (5-MeODMT) and p-chloroamphetamine (PCA) in male BK. TO mice. The effects of depleting brain 5-hydroxytryptamine (5-HT) with p-chlorophenylalanine (PCPA) on the 5-MeODMT in the mouse were also studied. Changes in brain 5-HT and 5-hydroxyindoleacetic (5-HIAA) were concomitantly determined. PCPA (400 mg/kg IP twice on consecutive days) significantly increased the number of head twitches induced by 5-MeODMT (5 mg/kg IV) on days 3 and 5 after the initial injection of PCPA when 5-HT and 5-HIAA were also significantly reduced. On day 12, there was no significant difference in the number of head twitches between mice administered PCPA and those given saline, and 5-HT and 5-HIAA levels were nearly back to normal. PCPA, using the same dose schedule, significantly reduced the number of head twitches induced by PCA when PCA was administered 24 h after the second injection of PCPA (day 3. Mice maintained on a 12-h light-dark cycle showed a maximum response to the direct 5-HT receptor agonist 5-MeODMT (5 mg/kg IV) towards the end of the dark period, when the 5-HT level was at its lowest. p-Chloroamphetamine, which causes release of 5-HT from pre-synaptic neurones, produced a peak head twitch response in the middle of the light period when 5-HT and 5-HIAA levels were maximal, while the response towards the end of the dark period was significantly less than that at other times tested. It is concluded that 5-HT receptor response shows a circadian rhythm related to both pre-synaptic availability of 5-HT and post-synaptic receptor sensitivity.
mesh_terms: D000662:Amphetamines / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001923:Brain Chemistry / Q000187:drug effects; D002940:Circadian Rhythm; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D008732:Methoxydimethyltryptamines / Q000494:pharmacology*; D051379:Mice; D012701:Serotonin / Q000031:analogs & derivatives* / Q000378:metabolism; D010133:p-Chloroamphetamine / Q000494:pharmacology*
chemical_list: D000662:Amphetamines; D008732:Methoxydimethyltryptamines; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D010133:p-Chloroamphetamine