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Brain regional serotonergic activity: Effects of theophylline in non- tolerant and tolerant rat
Published in -
Volume: 4
Issue: 4
Pages: 283 - 293
A single administration of theophylline (Th) (10-20 mg-kg, p.o.) to adult male albino rats produced a dose dependent increase in locomotor activity (LA). Th-induced stimulation of LA was found to be maximum following 4 consecutive days of Th (10-20 mg/kg/day, p.o.) treatment under similar condition. The administration (once/ day, p.o.) of Th (10 mg/kg/day, p.o.) for 16 consecutive days developed tolerance to LA. Biochemical studies showed that in Th non-tolerant conditions the steady state level of 5-HT anti pargyline-induced accumulation of 5-HT was increased in the cerebral cortex, cerebellum and pons-medulla, with the decrease of their steady state level of 5-HIAA, MAO activity and probenecid-induced accumulation of 5-HIAA: No appreciable change was observed in pargyline-induced declination of 5-HIAA in the brain regions of Th non-tolerant rats. Unlike Th non-tolerant conditions, the development of tolerance to Th produced no change in any of the parameters of serotonergic system in those brain regions. These results thus suggest that (a) Th-induced stimulation of LA in nontolerant rats may be mediated through the inhibition of those brain regional serotonergic activity and (b) restoration of this inhibition in brain regional serotonergic activity due to 16 consecutive days of Th treatment leads to the development of tolerance to LA.
About the journal
JournalJournal of Serotonin Research