Neuroprotective effects of quinpirole on lithium chloride pilocarpine-induced epilepsy in rats and its underlying mechanisms

Abstract

Introduction: Epilepsy is a common neurological disorder that presents with challenging mechanisms and treatment strategies. This study investigated the neuroprotective effects of quinpirole on lithium chloride pilocarpine-induced epileptic rats and explored its potential mechanisms.

Methods: Lithium chloride pilocarpine was used to induce an epileptic model in rats, and the effects of quinpirole on seizure symptoms and cognitive function were evaluated. The Racine scoring method, electroencephalography, and Morris water maze test were used to assess seizure severity and learning and memory functions in rats in the epileptic group. Additionally, immunohistochemistry and Western blot techniques were used to analyze the protein expression levels and morphological changes in glutamate receptor 2 (GluR2; GRIA2), BAX, and BCL2 in the hippocampi of rats in the epileptic group.

Results: First, it was confirmed that the symptoms in rats in the epileptic group were consistent with features of epilepsy. Furthermore, these rats demonstrated decreased learning and memory function in the Morris water maze test. Additionally, gene and protein levels of GluR2 in the hippocampi of rats in the epileptic group were significantly reduced. Quinpirole treatment significantly delayed seizure onset and decreased the mortality rate after the induction of a seizure. Furthermore, electroencephalography showed a significant decrease in the frequency of the spike waves. In the Morris water maze test, rats from the quinpirole treatment group demonstrated a shorter latency period to reach the platform and an increased number of crossings through the target quadrant. Network pharmacology analysis revealed a close association between quinpirole and GluR2 as well as its involvement in the cAMP signaling pathway, cocaine addiction, and dopaminergic synapses. Furthermore, immunohistochemistry and Western blot analysis showed that quinpirole treatment resulted in a denser arrangement and a more regular morphology of the granule cells in the hippocampi of rats in the epileptic group. Additionally, quinpirole treatment decreased the protein expression of BAX and increased the protein expression of BCL2.

Conclusion: The current study demonstrated that quinpirole exerted neuroprotective effects in the epileptic rat model induced by lithium chloride pilocarpine. Additionally, it was found that the treatment not only alleviated the rats' seizure symptoms, but also improved their learning and memory abilities. This improvement was linked to the modulation of protein expression levels of GLUR2, BAX, and BCL2. These findings provided clues that would be important for further investigation of the therapeutic potential of quinpirole and its underlying mechanisms for epilepsy treatment.

Keywords: BAX; BCL2; Epilepsy; GluR2; Neuroprotection; Quinpirole.

Fig. 1

The seizure group exhibited typical features of a seizure. The water maze confirmed the presence of learning and memory impairments in the seizure group. A-D The seizure group exhibiting typical features of a seizure. E NC group in the water maze. F Seizure group in the water maze. G Statistical analysis of escape latency before modeling. H Statistical analysis of escape latency after modeling. Each group N = 3, *: P < 0.05

Fig. 2

After 72 h of seizure occurrence, the expression of GluR2 significantly decreases in the hippocampus. A Western blot analysis showed that the protein expression of GluR2 in the hippocampi of rats in the seizure group was significantly downregulated 72 h after the occurrence of the seizure. B Quantitative Western blot analysis results for GLUR2 protein. C PCR confirmed that the expression of the GluR2 gene in the hippocampi of rats in the seizure group was significantly downregulated 72 h after the occurrence of the seizure. D Immunohistochemical analysis of GLUR2 in the NC group. E Immunohistochemical analysis of GLUR2 in the seizures (72H) group. F Quantitative results of immunohistochemistry between the two groups. Each group N = 3, *: P < 0.05

Fig. 3

Electroencephalogram and water maze results after the action of quinpirole in an epilepsy model and its network pharmacology analysis. A Electroencephalogram and water maze results in the NC group. B Electroencephalogram and water maze results in the quinpirole group. C Electroencephalogram and water maze results in the seizures group. D The occurrence of epileptic seizures was recorded during the electroencephalogram (EEG) monitoring period. E The comparison of water maze results among the three groups. F Molecular structure diagram of quinpirole. G STRING database of proteins that interact with GRIA2. H Protein Interaction Network Analysis database of proteins that interact with GRIA2. I KEGG analysis of proteins interacting with GRIA2. N = 3 in each group, *: P < 0.05

Fig. 4

Pathologic changes and apoptosis-related proteins after the action of quinpirole in a seizure model. A Hematoxylin and eosin staining and immunohistochemical staining after the action of quinpirole in a model of epilepsy. B Quantitative immunohistochemistry results. C Quinpirole acts on GLUR2 and apoptosis-related proteins in the epileptic group as detected by Western blot. D Quantitative results of Western blot analysis. Each group N = 3, *: P < 0.05