Chronic treatment with the antidepressant desipramine consistently reduced pain relief caused by 5-MeODMT in rats across several pain tests, while chronic amitriptyline sometimes increased that pain relief. Acute antidepressant treatment raised shock thresholds in rats not given 5-MeODMT, but effects differed from chronic treatment. The findings highlight that acute and chronic antidepressant effects on pain perception are distinct.
An injection of the serotonin agonist drug 5-methoxy-N,N-dimethyltryptamine in rats lengthened both the time until and the duration of convulsions triggered by decapitation, starting at a dose of 0.5 mg/kg. Pretreatment with the serotonin antagonist methergoline (2.0 mg/kg) partially blocked these effects. Long-term administration of p-chloroamphetamine or p-chlorophenylalanine did not counteract the drug's effects but independently prolonged convulsion duration. The authors suggest the method may be useful for studying serotonin receptor mechanisms.