C-Fos expression in epileptogenic areas of nephropathic rats undergoing star fruit poisoning

Abstract

Purpose Studies have demonstrated that star fruit consumption by nephropathic patients triggers severe neurotoxic effects that can lead to convulsions or even death. Brain areas likely susceptible to star fruit poisoning have not been investigated. The objective of the present study was to map possible epileptogenic areas susceptible to star fruit intoxication in nephropathic rats. Methods The study analyzed 25 rats (5 groups). Rats in the experimental group underwent bilateral ureteral obstruction surgery and orogastric gavages with star fruit juice. An electroencephalogram was used to confirm convulsive seizures. Urea and creatinine levels were used to confirm the uremia model. Immunohistochemical analysis was used to map cells with c-Fos protein (c-Fos+ cells) to identify brain areas with increased neuronal activity. Control groups included non-nephropathic and nephropathic rats that did not receive star fruit. Results A statistically significant increase (p<0.01) in c-Fos+ cells was noted in nephropathic animals receiving star fruit juice compared to control groups, in brain areas commonly related to epileptogenic neural circuits including the hippocampus, amygdala, rhinal cortex, anterior cingulate area, piriform area, and medial dorsal thalamus. Conclusion These data corroborate the neurotoxic capacity of star fruit in nephropathic patients.

Figure 1. Recordings of electrical activity in the brain of a nephropathic animal that underwent a first gavage with star fruit ( left ) and during a seizure attack ( right ). On the left, the presence of spindles, as exemplified between 265 and 266, and theta waves, characteristic of relaxed wakefulness, can be seen. Periods characterized by desynchronized waves are also present. During the seizure ( right ), a prolonged cluster of spikes with little organization, and increased frequency and amplitudes over time can be seen.

Figure 2. Photomicrograph of rat brain cross-sections that have undergone immunohistochemistry to identify c-Fos protein expression. The figures on the left (A, C, E, G) are from the white groups (WHI). The figures on the right (B, D, F, H) are from the nephropathic star fruit groups (NPS). A/B: Amygdala; C/D: region of the thalamic nuclei, dorsal part of the anteromedial nucleus, anteroventral nucleus, interanteromedial nucleus, paraventricular nucleus, and ventral anterolateral complex (AMd, AV, IAM, PVT, and VAL, respectively); E/F: entorhinal, perirhinal, and entorhinal areas (ENTI, PERI, and ECT, respectively); G/H: piriform area (PIR). There is greater c-Fos expression in the nephropathic groups.

Figure 3. Photomicrograph of cross-sections of the rat brain that have undergone immunohistochemistry to identify c-Fos protein expression. The figures on the left (A, C, E) are from the white groups (WHI). The figures on the right (B, D and F) are from the nephropathic star fruit groups (NPS). A/B: areas of the dentate gyrus (DG); C/D: ventral region of the hippocampus, Ammon’s horn, and CA3 and CA1 fields (CA3 and CA1); E/F: anterior cingulate area, dorsal part (ACAd). There is greater c-Fos expression in the nephropathic groups.

Figure 4. Graph representing the number of cells per counting area. Hp (hippocampus); ENTI, PERI, and ECT (entorhinal, perirhinal, and entorhinal areas, respectively); PIR (piriform area); ACAd (anterior cingulate area, dorsal part); Am (amygdala). Tal (thalamus).

Figure 5. Pathway map summarizing the connections involving c-Fos expression in seizure-related areas of NPS rats. ACAd (anterior cingulate area, dorsal part). AMd, AV, IAM, PVT, and VAL (region of the thalamic nuclei, dorsal part of the anteromedial nucleus, anteroventral nucleus, interanteromedial nucleus, respectively).