Involvement of GABAA receptors of lateral habenula in the acquisition and expression phases of morphine-induced place preference in male rats.

The lateral habenula (LHb) is a critical brain structure involved in the aversive response to drug abuse. It has been determined that the gamma-aminobutyric acid (GABA)-ergic system plays the main role in morphine dependency. The role of GABA type A receptors (GABAARs) in LHb on morphine-induced conditioned place preference (CPP) remains unknown. In this study, the effect of bilateral intra-LHb microinjection of GABAAR agonist and antagonist on the acquisition and expression phases of CPP, utilizing a 5-day CPP paradigm in male rats, was evaluated. Subcutaneous administration of different doses of morphine caused a dose-dependent CPP. Intra-LHb microinjection of the GABAAR agonist, muscimol, in combination with morphine (5 mg/kg; subcutaneously) enhanced CPP scores in the acquisition phase of morphine CPP, whereas the GABAAR antagonist, bicuculline, significantly reduced the conditioning scores in the acquisition phase. Furthermore, pretreatment with a high dose of bicuculline reversed the additive effect of muscimol during the acquisition phase, yet the low dose of antagonist had no significant effect on agonist-induced CPP scores. On the other hand, muscimol (3 µg/rat) significantly increased CPP scores in the expression phase but bicuculline did not induce a significant effect on CPP scores. Bicuculline and muscimol microinjections did not affect locomotor activity in the testing sessions. Our results confirm that GABAARs in LHb play an active role in morphine reward. In addition, microinjections of bicuculline/muscimol may alter the morphine response through the GABAergic system.

The effect of hydro-alcoholic of Phoenix Dactylifera extract on sleep and EEG in rat.

OBJECTIVE: Hard envelope of date palm pollen is used as a sedative and calmative compounds in Iranian traditional medicine. We tried to study the effects of Phoenix dactylifera (Tarooneh) extract on sleep time and Brian waves. MATERIALS AND METHODS: Rats were divided into control and test groups in sleep experiment. Control groups included intact group (without any injection), negative control group (saline) and positive control group (midazolam 0.1 mg/kg). Test groups received three doses of Tarooneh extract (62.5, 125 and 250 mg/kg). Rat were placed in sleep physiograph system and recording started 20 min after 2-hr calming down. Four parameters including sleep time, awakening, most activity period and main sleep time interval were measured. In EEG experiment electrodes were placed under the cranium for EEG recording and waves were compared with their baselines. RESULTS: All doses of the extract increased sleeping time (p< 0.05) but just the dose of 250 mg/kg (p<0.05) and midazolam (p< 0.001) decreased the awakening time. EEG results showed that the dose of 125 mg/kg increased the low frequency waves (p< 0.05) and the dose of 250 mg/kg decreased high frequency waves of alpha and beta (p< 0.05). CONCLUSION: Due to these effect on sleeping time and EEG, Tarooneh extract consumption can be useful as a sedative agent in Iranian traditional medicine. According to this study, the doses of 125 and 250 mg/kg of the extract would be the appropriate doses to be further studied.

The effect of treadmill running on memory before and after the NBM-lesion in rats.

Some studies have shown the effects of exercise training in retarding onset and progression of memory deficit in neurodegenerative disorders such as Alzheimer's disease. In this research, we investigated the effect of treadmill running on memory function; before, after, and continually (before and after) the nucleus basalis magnocellularis lesions. 66 male rats were randomly divided into six groups, including control, sham operation, the NBM-lesion, exercise before the NBM-lesion, exercise after the NBM-lesion, and exercise before and after the NBM-lesion. Lesion was induced by 5 µg/µl bilateral injection of Ibotenic acid. Memory function was assessed by using the passive avoidance learning test. Our results showed that treadmill running delays cognitive decline in the NBM-lesion rats, prevented memory deficit, and has advantageous effects on short-term, intermediate and long-term memory. Exercising on a regular basis may impede memory loss significantly, which may be attributed to specific molecular pathways in the brain.