Recruitment of peripheral-type benzodiazepine receptors after acute stress in chick forebrain membranes: action of Triton X-100

Alterations in GABAergic function following forced swimming stress

Forced swimming induces alterations in the GABA brain concentration and could change the sensitivity of the GABA/benzodiazepine receptor-chloride ionophore complex to benzodiazepines. This change in sensitivity could be explained by the allopregnanolone release that takes place during stress. The current study was carried out to determine whether forced swimming is able to modify the anti-anxiety effect of diazepam and to explore the possible relation of this change to allopregnanolone, the GABA concentration or/and the GABA/benzodiazepine receptor density. Unstressed and stressed mice, injected with the vehicle or diazepam, were evaluated in the exploratory behavior test. Diazepam induced clear anxiolytic actions at all doses in unstressed animals, but such an effect was not observed in stressed animals. The injection of allopregnanolone 24 h before the anxiety test blocked the effect of this benzodiazepine. Forced swimming decreased GABA concentrations in the hippocampus and the thalamus-hypothalamus region, besides decreasing the [(3)H]flunitrazepam labeling in both the hypothalamus and amygdala. These results show that forced swimming abolishes the anti-anxiety effect of diazepam.

Benzodiazepine receptors and avian macrophage activity: diazepam decreases spreading and phagocytosis

The complex interrelations between the nervous system and the immune system have led to the creation of a new research area denoted neuroimmunology. The effects of stress on the immune response have long been observed in chickens. Since benzodiazepine receptors are involved in the stress reaction, we proposed to assess the importance of these receptors in the activity of chick peritoneal macrophages. We used 420 viable embryonated eggs of the commercial Hubbard broiler line treated through the chorioallantoid membrane on the 11th day of incubation: falsely manipulated (Sham group), with 40% propyleneglycol (PG) in simple Ringer solution (Vehicle group), and treated with diazepam (DZ), 8 mg/kg (DZ group). After hatching, the chicks were housed in metal rearing cages of the "battery" type for 5 weeks. At 36 days of age, 24 chicks from each treated group were divided at random into two groups of 12 animals each which were treated with DZ (2 mg/kg) or with 40% PPG in an equal volume once a day by the oral route for 4 days. Peritoneal macrophages were collected and submitted to the spreading an phagocytosis tests. Data were analyzed statistically using the SAS software (p < 0.05). Administration of DZ in ovo did not cause a significant decrease in egg hatchability, birth weight or performance parameters during the 5 weeks of assessment. However, the rate of macrophage spreading and phagocytosis was reduced. When administered at 40 days of age, DZ did not change the spreading rate but reduced the phagocytosis rate. There was no interaction between treatments. These results indicate that benzodiazepine receptors seem to be important for macrophage activity also in birds, as previously observed in rodents and primates. Since benzodiazepine receptors are involved in the response to stress, it is possible that the effects of stress on avian immunity may be mediated in part by these receptors.