Mescaline: excitatory effects on acoustic startle are blocked by serotonin2 antagonists.
The ability of serotonin2 (5-HT2) antagonists to block the excitatory effects of mescaline on the acoustic startle reflex were analyzed. Mescaline (20 mg/kg) caused a consistent increase in the amplitude of the acoustic startle reflex. This effect was blocked in a dose-related fashion by the 5-HT2 antagonist ritanserin (ED50 dose = 0.25 mg/kg IP). In contrast, even a high dose of ritanserin (2.0 mg/kg) did not block the excitatory effects of amphetamine on startle. Other 5-HT2 antagonists (ketanserin, cinanserin, LY 53857) also blocked mescaline's effect, whereas the 5-HT1 antagonist pindolol (5 mg/kg) did not. These results support the hypothesis that the behavioral effects of hallucinogens are mediated by agonist actions at 5-HT2 receptors.
D000818:Animals; D003913:Dextroamphetamine / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D008297:Male; D008635:Mescaline / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012022:Reflex, Acoustic / Q000187:drug effects*; D013216:Reflex, Startle / Q000187:drug effects*; D016713:Ritanserin; D012702:Serotonin Antagonists / Q000494:pharmacology*
D010880:Piperidines; D012702:Serotonin Antagonists; D016713:Ritanserin; D008635:Mescaline; D003913:Dextroamphetamine; D004121:Dimethyl Sulfoxide