Baixiangdan capsule and Shuyu capsule regulate anger-out and anger-in, respectively: GB1-mediated GABA can regulate 5-HT levels in multiple brain regions.

The identity of the mechanism by which the Baixiangdan capsule (BXD) and the Shuyu capsule (SY) control anger-out (AO) and anger-in (AI) in rodents is unclear. The current study clarified the intervention role of BXD and SY on AO and AI male rats. We further explored the differences between BXD and SY in the treatment of AO and AI rats. Social isolation combined with the resident-intruder paradigm was used to establish the anger-out and AI rats models. On this basis, GABA content in the dorsal raphe nucleus (DRN) and serotonin (5-HT) contents in these brain regions were detected using ELISA after various time courses (0, 1, 3, 5, and 7 days) treated with BXD and SY. Co-expression of 5-HT and GB1 in the DRN was detected. GB1-specific agonist baclofen and GB1-specific inhibitor CGP35348 were injected into the DRN. Changes in 5-HT levels in these brain regions were then detected. After treatment, rats in the BXD group exhibited lower aggressive behavior scores, longer latencies of aggression, lower total distances in the open field test, and a higher sucrose preference coefficient. Meanwhile, rats in the SY group exhibited higher aggressive behavior scores, shorter latencies of aggression, higher total distances in the open field test, and higher sucrose preference coefficients. With increasing medication duration, 5-HT levels in these brain regions were increased gradually, whereas GABA levels in the DRN were decreased gradually, and all recovered to normal levels by the 7th day. A large number of 5-HT-positive cells could be found in the immunofluorescence section in the DRN containing GABABR1 (GB1)-positive cells, indicating that 5-HT neurons in the DRN co-expressed with GB1. Furthermore, after the drug intervention, the 5-HT level in the DRN was elevated to a normal level, and the GB1 level in the DRN was decreased to a normal level. After the microinjection of baclofen into the DRN, the 5-HT contents in these brain regions were decreased. By contrast, the 5-HT contents were increased after injection with CGP35348. BXD and SY could effectively improve the abnormal behavior changes of AO and AI rats, and the optimal duration of action was 7 days. The improvement way is as follows: Decreased abnormal increase of GABA and GB1 in the DRN further mediated synaptic inhibition and increased 5-HT level in the DRN, leading to increased 5-HT levels in the PFC, hypothalamus, and hippocampus. Therefore, GB1-mediated GABA in the DRN could regulate 5-HT levels in these brain regions, which may be one of the ways by which BXD and SY treat AO and AI, respectively.

GABABR1 in DRN mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior.

The identity of the mechanism that controls aggressive behavior in rodents is unclear. Serotonin (5-HT) and GABA are associated with aggressive behavior in rodents. However, the regulatory relationship between these chemicals in the different brain regions of rats has not been fully defined. This study aimed to clarify the role of GABABR1 in DRN-mediated GABA to regulate 5-HT expression in multiple brain regions in male rats with high and low aggressive behavior. Rat models of highly and less aggressive behavior were established through social isolation plus resident intruder. On this basis, GABA content in the DRN and 5-HT contents in the PFC, hypothalamus, hippocampus and DRN were detected using ELISA. Co-expression of 5-HT and GB1 in the DRN was detected by immunofluorescence and immunoelectron microscopy at the tissue and subcellular levels, respectively. GB1-specific agonist baclofen and GB1-specific inhibitor CGP35348 were injected into the DRN by stereotaxic injection. Changes in 5-HT levels in the PFC, hypothalamus and hippocampus were detected afterward. After modeling, rats with highly aggressive behavior exhibited higher aggressive behavior scores, shorter latencies of aggression, and higher total distances in the open field test than rats with less aggressive behavior. The contents of 5-HT in the PFC, hypothalamus and hippocampus of rats with high and low aggressive behavior (no difference between the two groups) were significantly decreased, but the change in GABA content in the DRN was the opposite. GB1 granules could be found on synaptic membranes containing 5-HT granules, which indicated that 5-HT neurons in the DRN co-expressed with GB1, which also occurred in double immunofluorescence results. At the same time, we found that the expression of GB1 in the DRN of rats with high and low aggressive behavior was significantly increased, and the expression of GB1 in the DRN of rats with low aggressive behavior was significantly higher than that in rats with high aggressive behavior. Nevertheless, the expression of 5-HT in DRN was opposite in these two groups. After microinjection of baclofen into the DRN, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group decreased significantly. In contrast, the 5-HT contents in the PFC, hypothalamus and hippocampus of rats in each group increased significantly after injection with CGP35348. The significant increase in GABA in the DRN combined with the significant increase in GB1 in the DRN further mediated the synaptic inhibition effect, which reduced the 5-HT level of 5-HT neurons in the DRN, resulting in a significant decrease in 5-HT levels in the PFC, hypothalamus and hippocampus. Therefore, GB1-mediated GABA regulation of 5-HT levels in the PFC, hypothalamus and hippocampus is one of the mechanisms of highly and less aggressive behavior originating in the DRN. The increased GB1 level in the DRN of LA-behavior rats exhibited a greater degree of change than in the HA-group rats, which indicated that differently decreased 5-HT levels in the DRN may be the internal mechanisms of high and low aggression behaviors.