The effect of chronic and acute oral or intraperitoneal treatment with the
antidepressant drugs,
desipramine,
amitriptyline,
alaproclate and
iprindole, upon pain thresholds in the tail flick, hot plate and
shock titration tests of nociception in saline- and 5-MeODMT-treated rats was studied. Chronic
desipramine treatment increased the pre-test tail flick latencies. In the saline-treated rats, chronic oral
desipramine treatment increased tail flick latencies, whereas chronic oral
amitriptyline treatment decreased tail flick latencies. In 5-MeODMT-treated rats, chronic oral
desipramine treatment attenuated the effects of 5-MeODMT (1 mg/kg) in all three tests of nociception, whereas chronic
amitriptyline caused a potentiation in the tail flick and hot plate tests. Chronic oral
iprindole treatment attenuated 5-MeODMT-induced
analgesia in the hot plate test. Chronic intraperitoneal
desipramine treatment attenuated 5-MeODMT
analgesia in the tail flick and
shock titration tests. In a different chronic treatment experiment, oral
desipramine treatment attenuated 5-MeODMT
analgesia in the tail flick test and
zimeldine did for both the tail flick and hot plate tests, whereas
mianserin potentiated 5-MeODMT-induced
analgesia in both the tail flick and hot plate tests. In the saline-treated rats, acute treatment with all four drugs,
desipramine,
amitriptyline,
iprindole and
alaproclate, elevated the
shock thresholds, whereas in 5-MeODMT-treated rats,
desipramine and
amitriptyline elevated
shock thresholds. Two main conclusions can be drawn: chronic
desipramine caused a quite consistent attenuation of 5-MeODMT-induced
analgesia and the effects of acute treatment differed strongly from that of the chronic treatment. The effects of chronic administration with these
antidepressants were compared with other findings using different measures of behavioural and receptor function.