Resident intruder paradigm-induced aggression relieves depressive-like behaviors in male rats subjected to chronic mild stress

Profiling GABA(A) Receptor Subunit Expression in the Hippocampus of PMDD Rat Models Based on TCM Theories

γ-Aminobutyric acid type A receptors (GABAARs) play an important role in cognitive and emotional regulation and are related to the hippocampus. However, little is known regarding patterns of hippocampal GABAAR subunit expression in rat models of premenstrual dysphoric disorder (PMDD). This study investigated the above changes by establishing two PMDD rat models based on Traditional Chinese Medicine (TCM) theories, namely, PMDD liver-qi invasion syndrome (PMDD-LIS) and PMDD liver-qi depression syndrome (PMDD-LDS). Behavioral tests were used to detect depression and irritability emotion. Western blot analysis was used to investigate protein levels of GABAAR α1, α2, α4, α5, β2, β3, and δ subunits, whereas ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis was performed to determine gamma-aminobutyric acid (GABA) and glutamate (Glu) levels in the hippocampus across each group. Concurrently, behavioral data indicated that the PMDD-LDS and PMDD-LIS rat models had been successfully established. GABAAR α2, α5, β2, and δ subunit was significantly upregulated, whereas α4 was significantly downregulated (P < 0.05) in PMDD-LDS rat models relative to controls. On the other hand, GABAAR α1, α2, and β3 were significantly downregulated while α4 and β2 were significantly upregulated in PMDD-LIS rat models relative to the control group (P < 0.05). Moreover, GABA levels significantly decreased, while Glu and the ratio of glutamate to GABA increased in PMDD-LIS rat models (P < 0.05). Conversely, GABA and Glu levels significantly decreased, whereas the ratio of glutamate to GABA increased in PMDD-LIS rat models (P < 0.05). Conclusively, our results revealed differential expression of GABAAR α1, α2, α4, α5, β2, β3, and δ subunits between PMDD-LIS and PMDD-LDS rat models, suggesting that they may be biomarkers in the pathogenesis of PMDD.

Evaluation of the Effect of Hypericum triquetrifolium Turra on Memory Impairment Induced by Chronic Psychosocial Stress in Rats: Role of BDNF

Background

Chronic psychosocial stress impairs memory function and leads to a depression-like phenotype induced by a persistent status of oxidative stress. Hypericum perforatum L. (St. John's wort) is widely used to relieve symptoms of anxiety and depression; however, its long-term use is associated with adverse effects. Hypericum triquetrifolium Turra is closely related to H. perforatum. Both plants belong to Hypericaceae family and share many biologically active compounds. Previous work by our group showed that methanolic extracts of H. triquetrifolium have potent antioxidant activity as well as high hypericin content, a component that proved to have stress-relieving and antidepressant effects by other studies. Therefore, we hypothesized that H. triquetrifolium would reduce stress-induced cognitive impairment in a rat model of chronic stress.

Objective

To determine whether chronic treatment with H. triquetrifolium protects against stress-associated memory deficits and to investigate a possible mechanism.

Methods

The radial arm water maze (RAWM) was used to test learning and memory in rats exposed to daily stress using the resident-intruder paradigm. Stressed and unstressed rats received chronic H. triquetrifolium or vehicle. We also measured levels of brain-derived neurotrophic factor (BDNF) in the hippocampus, cortex and cerebellum.

Results

Neither chronic stress nor chronic H. triquetrifolium administration affected performance during acquisition. However, memory tests in the RAWM showed that chronic stress impaired different post-encoding memory stages. H. triquetrifolium prevented this impairment. Furthermore, hippocampal BDNF levels were markedly lower in stressed animals than in unstressed animals, and chronic administration of H triquetrifolium chronic administration protected against this reduction. No significant difference was observed in the effects of chronic stress and/or H. triquetrifolium treatment on BDNF levels in the cerebellum and cortex.

Conclusion

H. triquetrifolium extract can oppose stress-associated hippocampus-dependent memory deficits in a mechanism that may involve BDNF in the hippocampus.

Influence of Diazepino[1,2-a]benzimidazole derivative (DAB-19) on behavioral aspects of animals

Introduction: Diazepino[1,2-a]benzimidazole derivatives showed anxiolytic (EPM, L/D box, Vogel test), antidepressant (Tail Suspension test, Porsolt test), anticonvulsant (Pentylenetetrazole-Induced seizures) and analgesic (Tail-Flick, Hot Plate) actions, which were described earlier (Spasov et al. 2020). 11-(4-tert-butylbenzyl)-2,3,4,5-tetrahydro[1,3]diazepino[1,2-a]benzimidazole hydrobromide (compound DAB-19) has evident anxiolytic, antidepressant and anticonvulsant effects. In the present study, compound DAB-19 was screened for its influence on animals` behavior patterns, such as aggression, obsessive-compulsive behavior, emotional lability, and unsociability.

Materials and methods: 112 outbred white animals (rats and mice) were used. Compound DAB-19 (2.34 mg/kg, p.o.) and diazepam (2 mg/kg, p.o.) were injected to the treatment groups. Using an Open Field (OF) test, we evaluated a spontaneous motor activity, a search activity of mice and a degree of their emotionality. During a Marble Burying (MB) test, we monitored anxiolytic and anticompulsive effects of DAB-19. Using a Resident-intruder (RI) test, we evaluated a degree of aggression in the experimental animals, properties of their social interaction, as well as defensive and individual behavior.

Results and discussion: Compound DAB-19 has positive influence on the search activity, mood stabilizing activity and antiaggressive actions. Administration of both DAB-19 (2.34 mg/kg, p.o.) and diazepam (2 mg/kg, p.o.) reduced anxiety-like behavior in OP, RI and MB tests, as indicated by a significantly increased number of entries to the center of OP; a decreased number of marbles buried in MB and reduced aggressive behavior in RI. It was stated that using DAB-19 leads to a decrease in affective reactions of the animals – aggression, obsessive-compulsive behavior, neurotic condition and emotional instability.

Conclusions: The compound (DAB-19) produces anxiolytic-like effects, compared with those of diazepam, in various anxiety paradigms.