Abstract
Previous investigations have revealed the role of GABAergic and serotonergic systems in the modulation of pain behavior. This research aimed to examine the effects of intracerebroventricular (i.c.v.) infusion of GABA(A) receptor agonist and antagonist as well as citalopram on pain behavior in male mice. For i.c.v. microinjection, a guide cannula was surgically implanted in the left lateral ventricle of male mice. Pain behavior was evaluated using a tail-flick test. Tail flick latency was measured in each experimental group of mice every 15 min (for 60 min). I.c.v. microinjection of muscimol (0.5 and 1 µg/mouse; GABA(A) receptor agonist) into the left lateral ventricle dose-dependently induced an antinociceptive effect. On the other hand, i.c.v. infusion of bicuculline (1 µg/mouse; GABA(A) receptor antagonist) induced a hyperalgesia response. Moreover, intraperitoneally (i.p.) administration of citalopram (8 mg/kg) produced an antinociceptive effect. Co-treatment of citalopram (8 mg/kg) along with muscimol (0.25 µg/mouse) or bicuculline (0.25 µg/mouse) potentiated the antinociceptive effect produced by citalopram. We found an additive antinociceptive effect of citalopram and muscimol in male mice. In conclusion, our results suggested an interaction between citalopram and GABAergic agents on the modulation of pain behavior in male mice.