Field: Neurophysiology and psychophysiology.
Dorsal hippocampal opioidergic system modulates anxiety-like behaviors in adult male Wistar rats
Article first published online: 28 OCT 2010
© 2010 The Authors. Psychiatry and Clinical Neurosciences © 2010 Japanese Society of Psychiatry and Neurology
Psychiatry and Clinical Neurosciences
Volume 64, Issue 6, pages 634–641, December 2010
How to Cite
Solati, J., Zarrindast, M.-R. and Salari, A.-A. (2010), Dorsal hippocampal opioidergic system modulates anxiety-like behaviors in adult male Wistar rats. Psychiatry and Clinical Neurosciences, 64: 634–641. doi: 10.1111/j.1440-1819.2010.02143.x
- Issue published online: 25 NOV 2010
- Article first published online: 28 OCT 2010
- Received 25 March 2010; revised 11 August 2010; accepted 25 August 2010.
- μ-opioid receptor;
- δ-opioid receptor;
- dorsal hippocampus;
Aims: In the present study, we investigated the possible influence of the opioidergic system of the dorsal hippocampus on anxiety-like behaviors.
Methods: Elevated plus-maze, which is one of the methods used for testing anxiety, was used in the present study. Rats were anesthetized with ketamine and xylazine and special cannulas were inserted stereotaxically into the CA1 region of the dorsal hippocampus. After 1 week of recovery, the effects of intra-CA1 administration of morphine (0.25, 0.5, 1 and 2 µg/rat; 1 µl/rat; 0.5 µl/in each side), naloxone (2, 4, 6 and 8 µg/rat), enkephalin (1, 2, 5 and 10 µg/rat) and naltrindole (0.25, 0.5, 1 and 2 µg/rat) on percentage open arm time (%OAT) and percentage open arm entries (%OAE) were determined.
Results: Bilateral administration of morphine into CA1 decreases %OAT and %OAE, indicating an anxiogenic-like effect. Intra-CA1 injection of naloxone, an opioid receptor antagonist, increased both %OAT and %OAE, parameters of anxiolytic-like behavior. Bilateral administration of δ-opioid receptor agonist, [D-Pen2,5]-enkephalin acetate hydrate into the CA1, induced an anxiolytic-like effect. Furthermore, intra-CA1 injection of δ-opioid receptor antagonist, naltrindole hydrochloride, increased anxiety-related behaviors.
Conclusions: The results of the present study demonstrate that activation of μ-opioid receptors in this area produce an anxiogenic response while activation of δ-opioid receptors produces an anxiolytic response.