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| Paper IPM / Cognitive / 8957 |
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| Abstract: | |||||||||
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In the present study, the influence of opioidergic system of the ventral
hippocampus, the nucleus accumbens or the central amygdala on anxiety-related
behaviour was investigated in rats. As a model of anxiety, the elevated plus
maze which is a useful test to investigate the effects of anxiogenic or anxiolytic
drugs in rodents was used. Bilateral microinjection of different doses of
morphine (2.5, 5 and 7.5 μg/rat) into the ventral hippocampus or the nucleus
accumbens increased open arm time (not locomotor activity, indicating an anxiolytic response. However, intra-central
amygdala administration of the opioid did not show any response. On the other
hand, microinjection of a dose of naloxone into the ventral hippocampus (2
μg/rat) or the nucleus accumbens (1 μg/rat) increased open arm time (but not open arm entry (administration of naloxone (0.5, 1 and 2 μg/rat) reversed the anxiolytic
effect of morphine (7.5 μg/rat) injected into the ventral hippocampus in a dosedependent
manner. A dose of the antagonist (1 μg/rat) also reduced the
morphine response (2.5 μg/rat) when injected in the nucleus accumbens. In
conclusion, it seems that the opioidergic system in the ventral hippocampus and
the nucleus accumbens are involved in anxiety-related behaviors and the ventral
hippocampus may be the main site of action of the anxiolytic properties of
morphine.
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