Down regulation of the hippocampal ghrelin receptor type-1a during electrical kindling-induced epileptogenesis

The causal association between epilepsy and amyotrophic lateral sclerosis: A two-sample Mendelian randomization study

OBJECTIVES

Epilepsy and amyotrophic lateral sclerosis (ALS) are common neurological disorders. The association between the two disorders has been raised in observational studies. However, it is uncertain to what extent they have mutual causal effects. In this study, we aimed to investigate their causal association using a two-sample Mendelian randomization (MR) method.

METHODS

We performed a two-sample bidirectional MR analysis to evaluate the causal association of epilepsy with the risk of ALS. Publicly published genome-wide association study statistics for epilepsy and ALS were used in the study. The primary analysis included genetic variants with a p value of less than 1 × 10-5 as instrumental variables. We applied several alternative methods, including inverse variance weighting, weighted median, simple mode, weighted mode, MR-Egger regression and MR pleiotropy residual sum and outlier, and statistical graphs to assess the associations of epilepsy and its subtype with the risk of ALS. Reverse MR analyses were also performed to examine the association of ALS with the risk of epilepsy.

RESULTS

The primary MR analysis found no causal effect of epilepsy on risk of ALS (odds ration [OR]: 1.133, 95% confidence interval [CI]: 0.964-1.332, p = .130). Among subtypes of epilepsy, it also failed to observe any causal association between general epilepsy and ALS (OR: 1.036, 95% CI: 0.969-1.108, P = .300). However, focal epilepsy contributed to an increase in the risk of ALS (OR: 1.177, 95% CI: 1.027-1.348, p = .019). Moreover, the investigation of reverse causalities did not reveal significant results.

CONCLUSIONS

The current study supports a causal influence of focal epilepsy on ALS risk. Future studies are needed to explore its potential role in ALS.

Step-by-step approach: Stereotaxic surgery for in vivo extracellular field potential recording at the rat Schaffer collateral-CA1 synapse using the eLab system

In vivo extracellular field potential recording is a commonly used technique in modern neuroscience research. The success of long-term electrophysiological recordings often depends on the quality of the implantation surgery. However, there is limited use of visually guided stereotaxic neurosurgery and the application of the eLab/ePulse electrophysiology system in rodent models. This study presents a practical and functional manual guide for surgical electrode implantation in rodent models using the eLab/ePulse electrophysiology system for recording and stimulation purposes to assess neuronal functionality and synaptic plasticity. The evaluation parameters included the input/output function (IO), paired-pulse facilitation or depression (PPF/PPD), long-term potentiation (LTP), and long-term depression (LTD).•Provides a detailed picture-guided procedure for conducting in vivo stereotaxic neurosurgery.•Specifically covers the insertion of hippocampal electrodes and the recording of evoked extracellular field potentials.

Differential impact of a ghrelin receptor antagonist or inverse agonist in the electrical kindling model of epilepsy

Ghrelin is a peptide, which has been shown to affect seizures. However, there is not a consensus about its real impact on the control of seizure severity. We assessed the influence of intra-amygdala injections of a ghrelin receptor (GHSR) antagonist, as well as a GHSR inverse agonist on the electrical kindling-induced seizures. Two unipolar electrodes and a tripolar electrode twisted with a guide cannula were implanted in the skull surface or the basolateral amygdala of adult male rats, respectively. A rapid electrical kindling protocol was applied for kindling epileptogenesis. The stimulations were applied until rats showed three consecutive stage five seizures. Each rat was considered as its control. D-Lys-3-GHRP-6 (1, 12.5, and 25 μg/rat) or [D-Arg, D-phe, D-Trp, heu] substance P (D-SP) (50, 500 and 5000 ng/rat) as the GHSR antagonist or inverse agonist were injected into the basolateral amygdala. Seizure parameters including after-discharge duration (ADD), stage five duration (S5D), and seizure stage (SS) were documented thirty minutes following administration of the drugs or saline. Antagonism of the GHSR in the amygdala, significantly increased seizure induction in the kindled rats, in a dose-dependent manner, and induced spontaneous seizures leading to status epilepticus. Conversely, D-SP had a dose-dependent anticonvulsant activity, indicated by decreased ADD and S5D. The results show that GHSR inverse agonism suppressed seizure severity in the rat amygdala kindling model, whereas GHSR antagonism made seizures more severe. Therefore, when considering the ghrelin system to modulate seizures, it is crucial to note the differential impact of various GHSR ligands.