Histological, Immunohistochemical, and Biochemical Assessment of the Amygdala in Tramadol-Induced Neurotoxicity

Abstract

Herbal Tramadol, a synthetic opioid analgesic widely used for pain management, is increasingly associated with neurotoxicity due to oxidative stress, particularly affecting the amygdala, a key brain region for emotional processing, fear response, and memory modulation. This study investigates the dose-dependent effects of tramadol on amygdala integrity in adult albino mice, focusing on histological, immunohistochemical, and biochemical alterations. Eighteen mice were divided into three groups (n=6 per group): Group 1 (Control, distilled water), Group 2 (Tramadol 20 mg/kg body weight), and Group 3 (Tramadol 40 mg/kg body weight), treated daily for three weeks. Hematoxylin and eosin (H&E) staining assessed neuronal morphology, glial fibrillary acidic protein (GFAP) immunohistochemistry evaluated astrocyte reactivity, and biochemical assays measured oxidative stress markers (glutathione, superoxide dismutase, catalase, malondialdehyde [MDA]). Results revealed dose-dependent neuronal damage, with Group 3 showing severe pyknotic nuclei, cytoplasmic vacuolation, and spongiform neuropil. GFAP staining indicated progressive astrocyte hypertrophy and gliosis, most pronounced in Group 3, reflecting robust neuroinflammation. Biochemical analyses showed significant reductions in antioxidants (glutathione, superoxide dismutase, catalase) and elevated MDA levels, with Group 3 exhibiting the most severe oxidative stress. These findings highlight tramadol’s neurotoxic potential in the amygdala, with higher doses exacerbating damage through oxidative and inflammatory pathways, underscoring the need for neuroprotective strategies.