Biology subjects

Woodhall, G.

Publications and source records attributed to Woodhall, G..

5 recordsLinked to original sources

bioRxiv2024

A GABA-A receptor response to CBD following status epilepticus in the medial entorhinal cortex of the rat

Cannabidiol is a non-psychoactive phytocannabinoid that has been implicated as a potential therapeutic in numerous neurological diseases. Perhaps the most widespread therapeutic use of CBD has been in the form of Epidiolex, which is used to treat seizures associated with Lennox-Gastaut syndrome, Dravet syndrome and tuberous sclerosis. Whilst the effectiveness of CBD in seizure reduction is clear, its mechanism of action is complex, and reflects the wide range of pharmacodynamic targets that includes receptors, ion channels and enzymes. This study investigated the effects of action of cannabidiol (CBD) on GABAergic transmission in layer II of the medial entorhinal cortex in animals that had previously undergone a period of status epilepticus (SE). Spontaneous post-synaptic currents were recorded from medial entorhinal cortex layer II pyramidal cells in animals 1-7 after SE and in age matched controls as well as in tissue resected from children with temporal lobe epilepsy (TLE). CBD enhanced GABAAR-mediated inhibition by increasing decay times and inhibitory charge transfer across the postsynaptic membrane in status epilepticus (SE) but did not alter GABAergic transmission in age-matched control rats. The SE-induced effects of CBD were blocked by ligands acting as inverse agonists at the benzodiazepine site of the GABAAR receptor and the effects of CBD were additive to low-doses of benzodiazepine and barbiturate agonists, consistent with allosteric actions on the GABAAR. Similar effects were observed in both SE rat and human layer II neurons. Overall, these data suggest CBD may act as a positive allosteric modulator (PAM) at postsynaptic GABAARs and this action appears to develop following SE. Key pointsO_LICBD increases inhibition only post status epilepticus. C_LIO_LIThis effect is blocked by benzodiazepine site inverse agonists C_LIO_LICBD is additive to low-dose zolpidem, suggesting an allosteric effect on the GABAAR C_LIO_LICBD was similarly effective in ex vivo human epileptic tissue C_LIO_LIThese results suggest CBD is a positive allosteric modulator at the GABAAR C_LI

neuroscience↗

bioRxiv2024

High-bandwidth, low-profile, long-term wireless EEG telemetry allows for optogenetic entrainment of natural cortical oscillations in freely-moving rats

Recording of whole-brain or multi-unit neuronal activity in the rodent brain is a powerful and widely used technique in neuroscience research. However, the acquisition of data from freely-moving animals is subject to a range of compromises. If a high bandwidth of data digitisation is needed, animals will either need to be tethered to the acquisition system or any telemetry used will have a short working battery life. For freely-moving experiments, especially those requiring careful behavioural measurements, such tethers and/or headstages incorporating e.g. optogenetic stimulation systems may prove to be confounding or limiting in the experiments which may be performed. Here we present the re[fi]nement and deployment of a wirelessly-charged, self-contained EEG telemeter at high data bandwidths (2kHz) with integrated optogenetic stimulator (473nm) and fully subcutaneous [fi]bre routing and implantation. This approach has allowed for rats to be recorded long-term (6 months) without requiring device explants, charging or maintenance, with an outward appearance identical to an unimplanted rodent. We have demonstrated the use of this system to stimulate cortical networks at a range of frequencies in freely-moving and acutely-anaesthetised rats allowing for the boosting or entrainment of physiological oscillations at will.

neuroscience↗

bioRxiv2023

Peripherally derived LGI1-reactive monoclonal antibodies cause epileptic seizures in vivo

One striking clinical hallmark in patients with autoantibodies to leucine-rich glioma inactivated 1 (LGI1) is the very frequent focal seizure semiologies, including faciobrachial dystonic seizures (FBDS), in addition to the amnesia. Polyclonal serum IgGs have successfully modelled the cognitive changes in vivo but not seizures. Hence, it remains unclear whether LGI1-autoantibodies are sufficient to cause seizures. We tested this with the molecularly precise monoclonal antibodies directed against LGI1 (LGI1-mAbs), derived from patient circulating B cells. These were directed towards both major domains of LGI1, LRR (n=5) and EPTP (n=5) and infused intracerebroventricularly over 7 days into juvenile male Wistar rats using osmotic pumps. Continuous wireless EEG was recorded from a depth electrode placed in hippocampal CA3 plus behavioural tests for memory and hyperexcitability were performed. Following infusion completion (Day 9), post-mortem brain slices were studied using electrophysiology and immunostaining. By comparison to control-mAb injected rats (n=6), video-EEG analysis over 9 days revealed convulsive and non-convulsive seizure activity in rats infused with LGI1-mAbs, with a significant number of ictal events (245{+/-}83 vs. 7.8{+/-}7.8 in controls; p=0.002). Memory was not impaired in the novel object recognition test. Local field potential recordings from postmortem brain slices showed spontaneous ictal-like spike activity in the CA3 region (p=0.03). The LGI1-mAbs bound most strongly in the hippocampal CA3 region and induced a significant reduction in Kv1.1 cluster number in this subfield (6 controls; 7 LGI1-mAbs; p=0.01) Peripherally-derived human LGI1-mAbs infused into rodent CSF provide strong evidence of direct in vivo epileptogenesis with molecular correlations. These findings fulfill criteria for LGI1-antibodies in seizure causation.

neuroscience↗

bioRxiv2022

Cannabidiol targets a modulatory system for excitatory-inhibitory synaptic coordination, contributing to its anti-seizure action

Cannabidiol (CBD), a non-euphoric component of cannabis, reduces seizures in multiple forms of pediatric epilepsy, but the mechanism(s) of anti-seizure action remain unclear. In one leading model, CBD acts at glutamatergic axon terminals, blocking pro-excitatory actions of an endogenous membrane phospholipid, lysophosphatidylinositol (LPI), at the G protein-coupled receptor GPR55. However, the impact of LPI-GPR55 signaling at inhibitory synapses and in epileptogenesis remains underexplored. We found that LPI transiently increased hippocampal CA3[->]CA1 excitatory presynaptic release probability and evoked synaptic strength in WT mice, while attenuating inhibitory postsynaptic strength by decreasing GABAAR{gamma}2 and gephyrin puncta. Effects of LPI at both excitatory and inhibitory synapses were eliminated by CBD pretreatment and absent after GPR55 deletion. Acute pentylenetrazole-induced seizures elevated levels of GPR55 and LPI, and chronic lithium pilocarpine-induced epileptogenesis potentiated the pro-excitatory effects of LPI. We propose that CBD exerts potential therapeutic effect both by blocking synaptic effects of LPI and dampening hyperexcitability.

neuroscience↗

bioRxiv2021

Encephalitis patient derived monoclonal GABAA receptor antibodies cause catatonia and epileptic seizures

Autoantibodies targeting the GABAA receptor (GABAAR) hallmark an autoimmune encephalitis presenting with frequent seizures and psychomotor abnormalities. Their pathogenic role is still not well-defined, given the common overlap with further autoantibodies and the lack of patient derived monoclonal antibodies (mAbs). We cloned and recombinantly produced five affinity-maturated GABAAR IgG1 mAbs from cerebrospinal fluid cells, which bound to various epitopes involving 1 and {gamma}2 receptor subunits, with variable binding strength and partial competition. mAbs selectively reduced GABAergic currents in neuronal cultures without causing receptor internalization. Cerebroventricular infusion of GABAAR mAbs and Fab fragments into rodents induced a severe phenotype with catatonia, seizures and increased mortality, reminiscent of encephalitis patients symptoms. Our results prove direct functional effects of autoantibodies on GABAARs and provide an animal model for GABAAR encephalitis. They further provide the scientific rationale for clinical treatments using antibody depletion and pave the way for future antibody-selective immunotherapies.

neuroscience↗