Evaluation of Retinal Histological Alterations Following Carbamazepine Administration in Adult Albino Wistar Rats.

Background Epilepsy is characterized by recurrent, unprovoked seizures and is a major global chronic neurological public health concern. Objective To evaluate retinal histological alterations, focusing on retinal ganglion cell count and apoptosis, following carbamazepine (CBZ) administration in adult albino Wistar rats. It is an antiepileptic drug mainly used for focal (partial) seizures, where it suppresses excessive neuronal firing by blocking voltage-gated Na⁺ channels. Study design A randomized, controlled experimental design was used. Methodology In the present study, 18 adult albino Wistar rats were given carbamazepine formulated in alkalinized sodium hydroxide (NaOH) according to their body weight. Following the experimental period, retinal tissues were harvested, fixed, and processed for immunohistochemical analysis using standard staining procedures and DAB (3,3'-diaminobenzidine) visualization. DAB visualization is a method in immunohistochemistry in which the DAB substrate reacts with the enzyme HRP (horseradish peroxidase) to produce an insoluble brown-colored precipitate at the site of the target antigen, allowing microscopic visualization and localization of the protein. Microscopic evaluation was performed to assess retinal ganglion cell density and apoptotic cell count per mm² across retinal layers using an ocular grid under 40X magnification. Animals were randomly divided into three groups (n=6 per group) using the balloting method. Group A was labelled as the control, while Groups B and C were labelled as experimental groups. Statistical analysis All the data were processed by SPSS v26.0 (IBM Corp., Armonk, USA). Kruskal-Wallis test was applied to compare means of scores, and one-way ANOVA was applied to compare means of numerical variables of all three groups. Results Retinal ganglion cell (RGC) count was observed to be reducing from the control group to experimental Group C. Mean±SD of RGC in Group A was 35.76±3.47, in Group B it was 27.80-±1.47, and in Group C it was 18.63±1.13. Results showed the difference was overall significant (p< 0.001). The control group showed few apoptotic sites, while experimental groups showed enhanced dose-dependent expression, which was moderate in Group B and greatly enhanced in Group C.  Conclusion We concluded that carbamazepine administration can result in dose-dependent histological alterations in the retina, including retinal ganglion cell loss, layer disorganization, and increased apoptosis, particularly in the retinal pigment epithelium. Further studies are recommended to investigate the underlying mechanisms and determine the long-term retinal safety of carbamazepine, particularly at higher doses.