Epilepsy is marked by seizures that are a manifestation of excessive brain activity and is symptomatically treatable by anti-epileptic drugs (AEDs). Unfortunately, the older AEDs have many side effects, with cognitive impairment being a major side effect that affects the daily lives of people with epilepsy. Thus, this study aimed to determine if newer AEDs (Zonisamide, Levetiracetam, Perampanel, Lamotrigine and Valproic Acid) also cause cognitive impairment, using a zebrafish model. Acute seizures were induced in zebrafish using pentylenetetrazol (PTZ) and cognitive function was assessed using the T-maze test of learning and memory. Neurotransmitter and gene expression levels related to epilepsy as well as learning and memory were also studied to provide a better understanding of the underlying processes. Ultimately, impaired cognitive function was seen in AED treated zebrafish, regardless of whether seizures were induced. A highly significant decrease in γ-Aminobutyric Acid (GABA) and glutamate levels was also discovered, although acetylcholine levels were more variable. The gene expression levels of Brain-Derived Neurotrophic Factor (BDNF), Neuropeptide Y (NPY) and Cyclic Adenosine Monophosphate (CAMP) Responsive Element Binding Protein 1 (CREB-1) were not found to be significantly different in AED treated zebrafish. Based on the experimental results, a decrease in brain glutamate levels due to AED treatment appears to be at least one of the major factors behind the observed cognitive impairment in the treated zebrafish.
The pharmacological inhibition of glial activation is one of the new approaches for combating neuropathic pain in which the role of glia in the modulation of neuropathic pain has attracted significant interest and attention. Neuron-glial crosstalk is achieved with N-methyl-D-aspartate-2B receptor (NMDAR-2B) activation. This study aims to determine the effect of ifenprodil, a potent noncompetitive NMDAR-2B antagonist, on activated microglia, brain-derived neurotrophic factors (BDNF) and downstream regulatory element antagonist modulator (DREAM) protein expression in the spinal cord of streptozotocin-induced painful diabetic neuropathy (PDN) rats following formalin injection. In this experimentation, 48 Sprague-Dawley male rats were randomly selected and divided into four groups: (n = 12): control, PDN, and ifenprodil-treated PDN rats at 0.5 μg or 1.0 μg for 7 days. Type I diabetes mellitus was then induced by injecting streptozotocin (60 mg/kg, i.p.) into the rats which were then over a 2-week period allowed to progress into the early phase of PDN. Ifenprodil was administered in PDN rats while saline was administered intrathecally in the control group. A formalin test was conducted during the fourth week to induce inflammatory nerve injury, in which the rats were sacrificed at 72 h post-formalin injection. The lumbar enlargement region (L4-L5) of the spinal cord was dissected for immunohistochemistry and western blot analyses. The results demonstrated a significant increase in formalin-induced flinching and licking behavior with an increased spinal expression of activated microglia, BDNF and DREAM proteins. It was also shown that the ifenprodil-treated rats following both doses reduced the extent of their flinching and duration of licking in PDN in a dose-dependent manner. As such, ifenprodil successfully demonstrated inhibition against microglia activation and suppressed the expression of BDNF and DREAM proteins in the spinal cord of PDN rats. In conclusion, ifenprodil may alleviate PDN by suppressing spinal microglia activation, BDNF and DREAM proteins.