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Animals were injected with 20 mg/kg desipramine (DMI) 1 h (acute) or 24, 5 and 1 h (subchronic) or once daily for 7 consecutive days (chronic) before the forced swimming test (FST). DMI was also injected at a dose of 40 mg/kg acutely. Animals were killed immediately after test for evaluation of brain concentrations of DMI and its demethylated metabolite desmethyldesipramine (DDMI). Acute and chronic DMI 20 mg/kg gave rise to similar brain concentrations but only chronic DMI was active on FST. Acute DMI 20 mg/kg and 40 mg/kg gave rise to different brain concentrations but similar effects on FST. DDMI concentrations were similar after the various DMI treatments. Results seem to indicate that no relationship exists between effect of DMI on FST and brain concentrations of either DMI or DDMI.

Summary. 8-OH-DPAT (2.5-10mg/kg) and buspirone (10 mg/kg) but not 5,7-DHT (200 gg/mouse), pCPA (75 and 150 mg/kg, three times), ritanserin (0.1 and 0.2mg/kg), LY 53857 (1.5 and 3mg/kg), GR38032F (0.1-100gg/kg), TFMPP (5 and 20mg/kg) and mCPP (2.5 and 5mg/kg) antagonized the rise in body temperature that occurs to the last mice removed from their group housing, which was termed as stress-induced hyperthennia (SIH). Ro 15-1788, at a dose which blocked the effect of diazepam on SIH, did not reverse the anxiolytic effect of buspirione. Instead, when cerebral 5-HT content was reduced to 50% by 5,7-DHT-induced lesion, the effect of buspirone on SIH was decreased. TFMPP 5 mg/kg did not shorten significantly the onset of SIH as could have been expected by an anxiogenic drug, while the dose of 20 mg/kg did not modify the pattern of SIH at all. The lower dose of TFMPP evoked a hyperthermic and the higher a hypothermic response.