Involvement of opioidergic system of the ventral hippocampus, the nucleus accumbens or the central amygdala in anxiety-related behavior.
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 microg/rat) into the ventral hippocampus or the nucleus accumbens increased the percentage of open arm time (%OAT) and open arm entries (%OAE) but 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 microg/rat) or the nucleus accumbens (1 microg/rat) increased open arm time (%OAT), but not open arm entry (%OAE) which may indicate an anxiolytic effect. Pre-treatment administration of naloxone (0.5, 1 and 2 microg/rat) reversed the anxiolytic effect of morphine (7.5 microg/rat) injected into the ventral hippocampus in a dose-dependent manner. A dose of the antagonist (1 microg/rat) also reduced the morphine response (2.5 microg/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.
Zarrindast
Mohammad-Reza
MR
Department of Pharmacology, School of Medicine, Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran. zarinmr@ams.ac.ir
Babapoor-Farrokhran
Sahand
S
Babapoor-Farrokhran
Savalan
S
Rezayof
Ameneh
A
D000679:Amygdala / Q000187:drug effects / Q000378:metabolism*; D000701:Analgesics, Opioid / Q000009:adverse effects / Q000494:pharmacology; D000818:Animals; D001007:Anxiety / Q000139:chemically induced / Q000378:metabolism*; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009020:Morphine / Q000009:adverse effects / Q000494:pharmacology; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011957:Receptors, Opioid / Q000819:agonists / Q000502:physiology*
D000701:Analgesics, Opioid; D011957:Receptors, Opioid; D009020:Morphine