Scopolamine-induced convulsions in fasted mice after food intake: effects of glucose intake, antimuscarinic activity and anticonvulsant drugs

Effects of scopolamine treatment and consequent convulsion development in c‑fos expression in fed, fasted, and refed mice

Fasting, anticholinergics, and seizures affect c‑fos activation in the brain. Additionally, antimuscarinic treated fasted animals develop convulsion soon after re‑feeding. Therefore, we assessed whether c‑fos expression changes in fed, fasting, and refed animals and how scopolamine treatment affects these changes. We further assessed whether there is a change in c‑fos expression after convulsions. For this purpose, BALB/c mice fasted for 1, 3, 6, 12, 24 and 48 h periods were used. The animals were treated with saline or scopolamine. Half\r\nof the animals treated with saline or scopolamine were given food 20 min after injection. All animals were observed for development of convulsions for 30 min. At the end of this period, the brains of all animals were removed, and the percentage of c‑fos active cells in the hypothalamus was determined immunohistochemically. Convulsions occurred within 1‑48 h of fasting, after scopolamine treatment and re‑feeding. Compared to fed animals, c‑fos expression was not significantly changed in those undergoing different fasting periods, but significantly decreased after 12 h fasting. After animals were allowed to eat, c‑fos activation significantly increased in the 1, 3, 6 and 12 refed‑saline groups and decreased in the 48 refed‑saline group. Scopolamine treatment in 1‑24 h fasted animals increased c‑fos expression, but decreased in 48 h fasted animals. Whereas convulsion development in scopolamine‑treated 3, 6, 12 and 24 h refed animals suppressed c‑fos expression. These results demonstrate that re‑feeding and scopolamine treatment induces neuronal activity in the hypothalamus, while scopolamine induced convulsions after food intake suppressed the c‑fos activity.

Contribution of M1 and M2 muscarinic receptor subtypes to convulsions in fasted mice treated with scopolamine and given food

Treatment of fasted mice and rats with the nonselective muscarinic antagonist, scopolamine or atropine, causes convulsions after food intake. This study evaluated the effect of fasting on the expression of M₁ and M₂ muscarinic receptors in the brain regions, the relationship between receptor expression and seizure stages, and the muscarinic receptor subtype which plays a role in the occurrence of convulsions. Mice were grouped as allowed to eat ad lib (fed) and deprived of food for 24h (fasted). Fasted animals developed convulsions after being treated with scopolamine (60%) or the selective M₁ receptor antagonist pirenzepine (10mg/kg; 20% and 60mg/kg; 70%) and given food. Fasting increased expression of M₁ receptors in the frontal cortex and M₂ receptors in the hippocampus, but produced no change in the expression of both receptors in the amygdaloid complex. Food intake after fasting decreased M₁ receptor expression in the frontal cortex and M₁ and M₂ receptor expression in the hippocampus. Seizure severity was uncorrelated with muscarinic receptor expression in the brain regions. Taken together, these findings provide evidence for the role of M₁ muscarinic receptor antagonism and fasting-induced increases in M₁ and M₂ expression possible underlying mechanism in the occurrence of convulsions in fasted animals.

"Eating" epilepsy revisited- an electro-clinico-radiological study

This study aimed to evaluate the clinical, video electroencephalographic and MRI attributes of patients with eating epilepsy (EE). Consecutive patients who were diagnosed with EE and underwent potential pre-surgical work-up from 2003 to 2012 formed the study cohort. Their electro-clinico-radiological and seizure outcome data were obtained from our prospectively maintained medical records. Out of 7094 patients who underwent evaluation for refractory seizures, 47 patients satisfied the criteria for EE. Twenty-three (48.9%) had exclusive EE; the remainder had a combination of predominantly eating-induced and unprovoked seizures with no differences noted in timing of seizures in relation to meals. Lesional epilepsy was seen in 34% of patients, with posterior cortex (PC; posterior temporo-parieto-occipital) predominance. In MRI negative patients, PC interictal epileptiform discharges were present in 34.4% of patients and multifocal in 20.6% of patients compared to the MRI positive group with 12.5% and 6.5%, respectively (p=0.003). Among 24 patients (51.1%) with co-existent unprovoked seizures, developmental delay and PC ictal onset was more prevalent (p=0.013 and 0.029) as compared to exclusive EE. The seizure frequency and outcome did not significantly differ between patients with or without MRI abnormality. Two patients underwent anterior temporal lobectomy, with persistence of their eating seizures postoperatively. EE is a complex reflex epilepsy of cryptogenic and symptomatic etiology. As opposed to the traditionally implied temporo-limbic mechanisms behind epileptogenesis, a multilobar network originating from the PC receiving sensory and visual inputs linked to the limbic-opercular pathways represents a plausible mechanism. Surgical selection should be diligent and cautious in this group of patients.

The role of solid food intake in antimuscarinic-induced convulsions in fasted mice

Animals treated with scopolamine after fasting develop convulsions after they are allowed to eat ad libitum. This study was aimed at investigating the effect on these convulsions of liquid food intake, feeding by gavage, and placebo. Fasted mice treated with saline or scopolamine were allowed to eat solid food, slurry food or liquid food ad libitum, given placebo, or given liquid food by gavage. After 30 min, all animals were allowed to eat food pellets and observed for 30 min for the incidence and onset of convulsions. Scopolamine treatment caused convulsions only in the animals given solid food in the first 30 min; no convulsions were observed in the animals given slurry food, liquid food ad libitum, gavage, or placebo. When the animals that did not develop convulsions during the experiment were allowed to eat solid food, convulsions occurred. These findings indicate that complex mechanisms trigger scopolamine-induced convulsions in fasted animals eating solid food.

The evaluation of antimuscarinic-induced convulsions in fasted rats after food intake

The present study was performed to evaluate convulsions after food intake in fasted rats pretreated with scopolamine or atropine and to determine whether these convulsions respond to drugs found effective in fasted mice. Scopolamine (2.4 mg/kg) and atropine (2.4 mg/kg) were given intraperitoneally (i.p.) to rats fasted for 52h. Both drugs induced convulsions after animals were allowed to eat ad lib. Another group of fasted rats pretreated with saline, MK-801 (0.1mg/kg), clonidine (0.1mg/kg), chlorpromazine (2 and 4 mg/kg), valproate (200mg/kg), diazepam (1.5 and 2mg/kg) or gabapentin (50mg/kg) were treated i.p. with saline or scopolamine (2.4 mg/kg) and were allowed to eat ad lib. Clonidine, MK-801, chlorpromazine (4 mg/kg) and diazepam (2 mg/kg) reduced the incidence of scopolamine-induced convulsions in fasted rats. Gabapentin could only prolong the onset of convulsions. Neither treatment was effective against myoclonus of hindlimbs. Present results showed that fasted rats also develop antimuscarinic-induced convulsions which do not completely respond to treatments found effective in convulsions of fasted mice.

Electroencephalographic characterization of scopolamine-induced convulsions in fasted mice after food intake

The present study was conducted to evaluate scopolamine-induced convulsions in fasted mice after food intake effects on the cortical electroencephalogram (EEG). Continuous EEG recordings were taken with Neuroscan for 10 min in freely moving mice with six chronic cortical electrode implants. Animals were weighed and deprived of food for 48 h. EEG recordings were taken at the 24th and 48th hour after their food deprivations. Later, all animals were treated with saline or scopolamine of 3mg/kg i.p. and EEG recordings were repeated for 10 min. Twenty minutes later, they were given food pellets and were allowed to eat ad libitum. All animals were observed for 60 min to determine the incidence and onset of convulsions and EEG recordings were taken simultaneously. The present results demonstrate that food deprivation causes differences in EEG in the elapsed time. The changes in EEG induced after food deprivation become different with scopolamine administration. In scopolamine treatment group, eating caused a series of high-voltage polyspikes and synchronized spikes with a predominant frequency in the 1-3 Hz range and fast activity that represents a typical epileptiform manifestation. It was concluded that the EEG properties and the behavioral patterns of these convulsions are in accordance with each other.