Influence of long-term zimelidine treatment on LSD-induced behavioural effects

Serotonergic mechanisms in the nucleus accumbens affected by chronic desipramine treatment

The effects of repeated treatment of rats with desipramine on 5-HT mechanisms within the nucleus accumbens (NAS) have been studied in a functional model. Local microinjections of 5-HT, quipazine as well as 5-HT1A receptor agonist buspirone, 8-OH-DPAT and NDO-008, inhibited rat locomotor activity in the open-field test. The effect of 5-HT and buspirone was blocked by serotonergic receptor antagonists methysergide and cyanopindolol, respectively. Chronic, but not acute treatment of rats with desipramine (10 mg/kg, PO, twice a day for 21 days, tests were performed 24 h after the last dose) significantly attenuated behavioral depression after 5-HT and quipazine microinjections, while the effect of buspirone was left unchanged. On the basis of present data, it may be concluded that whereas both accumbens 5-HT1A and 5-HT2 receptors appear to be important to regulation of animals' motility, only 5-HT2 receptors seem to be the most likely targets of antidepressive treatment. These data, along with previously reported changes in limbic noradrenergic and dopaminergic activity after antidepressive treatment, may explain the energizing influence of drugs and electroconvulsive shocks on psychomotor retardation, a part of endogenous depression.

Serotonin and depression: old problems and new data

1. Several lines of evidence implicating some dysfunction or alteration to brain serotonergic systems in depressive states are summarized. 2. Some aspects of the interactions between the 5-HT and catecholamine pathways in the action of antidepressant drugs are examined. 3. Finally, the important role of NA modulation of serotonergic activity in the action of antidepressants is suggested.

Chronic treatment with antidepressant drugs and the analgesia induced by 5-methoxy-N,N-dimethyltryptamine: attenuation by desipramine

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.