Transient Inactivation of Shell Part of Nucleus Accumbens Inhibits and Exacerbates Stress-Induced Metabolic Alterations in Wistar Rats

The controlling role of nitric oxide within the shell of nucleus accumbens in the stress-induced metabolic disturbance

CONTEXT AND OBJECTIVES

The involvement of the nitricergic system within the shell part of the nucleus accumbens (NAc) was evaluated in the metabolic disturbances due to stress.

MATERIALS AND METHODS

Male Wistar rats were cannulated in the shell of the left NAc. They received either saline or different doses of L-arginine and/or L-NAME five minutes before each stress session, for four days. Plasma cortisol concentration, food and water intake, time elapsing for eating, animal weight changes and adrenal gland weight were recorded.

RESULTS

The L-arginine 1 μg/rat decreased the level of cortisol, water and food intake and time of feeding and increased the adrenal weight. But L-NAME at 1 μg/rat had opposite effects on these factors. However, the drugs showed similar effects at 10 μg/rat.

CONCLUSION

Injection of nitric oxide modifiers into the left side of NAc shell part may have an interactive role with sub-chronic stress in metabolic behaviour.

The role of nucleus accumbens shell on acquisition and retrieval stages of morphine state dependent learning

AIM

In the present study, the effect of transient inactivation of the shell subregion of the nucleus accumbens (NAC shell) by lidocaine on the acquisition and retrieval stages of passive avoidance learning (PAL) and memory and morphine state-dependent learning (SDL) in male wistar rats was investigated.

METHODOLOGY

Adult male wistar rats weighing (220-250 g) were used. Lidocaine hydrochloride was bilaterally injected into the shell area of the nucleus accumbens 5 min before of subcutaneous morphine administration.

RESULTS

pre-training and pre-test infusion of lidocaine into the NAC shell significantly impaired PAL and memory. Furthermore, Pre-training administration of morphine (5 mg/kg, s.c.) in a step-through passive avoidance task induced state-dependent learning with impaired memory retrieval on the test day. The impairment of memory was restored after pre-test administration of the same dose of morphine. This phenomenon has been named as morphine state dependent learning (SDL). Moreover, Pre-training and pre-test inactivation of the NAC shell impaired morphine SDL.

CONCLUSIONS

The results suggest the role of NAC shell as a common structure in the PAL and morphine SDL. It is suggested that NAC shell as a common area plays a critical role in the acquisition and retrieval stages of PAL and also morphine SDL.

Deep brain stimulation in a rat model of post-traumatic stress disorder modifies forebrain neuronal activity and serum corticosterone

Objective(s):

Post-traumatic stress disorder (PTSD), one of the most devastating kinds of anxiety disorders, is the consequence of a traumatic event followed by intense fear. In rats with contextual fear conditioning (CFC), a model of PTSD caused by CFC (electrical foot shock chamber), deep brain stimulation (DBS) alleviates CFC abnormalities.

Materials and Methods:

Forty Male Wistar rats (220–250 g) were divided into 5 groups (n=8) and underwent stereotactic surgery to implant electrodes in the right basolateral nucleus of the amygdala (BLn). After 7 days, some animals received a foot shock, followed by another 7-day treatment schedule (DBS treatment). Next, freezing behavior was measured as a predicted response in the absence of the foot shock (re-exposure time). Blood serum corticosterone levels and amygdala c-Fos protein expression were assessed using Enzyme-linked immunosorbent assay (ELISA) and Western blot, respectively. Furthermore, freezing behaviors by re-exposure time test and general anxiety by elevated plus-maze (EPM) were evaluated.

Results:

PTSD decreased serum corticosterone levels and increased both amygdala c-Fos expression and freezing behaviors. Therefore, DBS treatment significantly (P<0.001) enhanced serum corticosterone levels and could significantly (P<0.001) reduce both c-Fos protein expression and freezing behaviors’ duration. However, DBS treatment has no effect on the general anxiety in PTSD rats.

Conclusion:

We argue that these outcomes might demonstrate the mechanism of DBS treatment, a complete therapeutic strategy, in PTSD patients.