Objective: Much evidence suggests that the subiculum plays a significant role in the regulation of epileptic activity. Lactate acts as a neuroprotective agent against many conditions that cause brain damage. During epileptic seizures, lactate formation reaches up to ~6 mmol/L in the brain. We investigated the effect of lactate on subicular pyramidal neurons after induction of epileptiform activity using 4-aminopyridine (4-AP-0Mg 2+ ) in an in vitro epilepsy model in rats. The signaling mechanism associated with the suppression of epileptiform discharges by lactate was also investigated. Methods: We used patch clamp electrophysiology recordings on rat subicular neurons of acute hippocampal slices. Immunohistochemistry was used for demonstrating the expression of hydroxycarboxylic acid receptor 1 (HCA1) in the subiculum. Results: Our study showed that application of 6 mmol/L lactate after induction of epileptiform activity reduced spike frequency (control 2.5 ± 1.23 Hz vs lactate 1.01 ± 0.91 Hz, P = .049) and hyperpolarized the subicular neurons (control −51.8 ± 1.9 mV vs lactate −57.2 ± 3.56 mV, P = .002) in whole cell patch-clamp experiments. After confirming the expression of HCA1 in subicular neurons, we demonstrated that lactate-mediated effect occurs via HCA1 by using its specific agonist. All values are mean ±SD. Electrophysiological recordings revealed the involvement of Gβγ and intracellular cAMP in the lactate-induced effect. Furthermore, current-clamp and voltage-clamp experiments showed that the G protein-coupled inwardly rectifying potassium (GIRK) channel blocker tertiapin-Q, negated the lactateinduced inhibitory effect, which confirmed that lactate application results in outward GIRK current. Significance: Our finding points toward the potential role of lactate as an anticonvulsant by showing lactate-induced suppression of epileptiform activity in subicular neurons. The study gives a different insight by suggesting importance of endogenous metabolite and associated signaling factors, which can aid in improving the present therapeutic approach for treating epilepsy.

No abstract

The structure of a new cysteine framework (-C-CC-C-C-C-) "M"-superfamily conotoxin, Mo3964, shows it to have a β-sandwich structure that is stabilized by inter-sheet cross disulfide bonds. Mo3964 decreases outward K(+) currents in rat dorsal root ganglion neurons and increases the reversal potential of the NaV1.2 channels. The structure of Mo3964 (PDB ID: 2MW7 ) is constructed from the disulfide connectivity pattern, i.e., 1-3, 2-5, and 4-6, that is hitherto undescribed for the "M"-superfamily conotoxins. The tertiary structural fold has not been described for any of the known conus peptides. NOE (549), dihedral angle (84), and hydrogen bond (28) restraints, obtained by measurement of (h3)JNC' scalar couplings, were used as input for structure calculation. The ensemble of structures showed a backbone root mean square deviation of 0.68 ± 0.18 Å, with 87% and 13% of the backbone dihedral (ϕ, ψ) angles lying in the most favored and additional allowed regions of the Ramachandran map. The conotoxin Mo3964 represents a new bioactive peptide fold that is stabilized by disulfide bonds and adds to the existing repertoire of scaffolds that can be used to design stable bioactive peptide molecules.

Objective Much evidence suggests that the subiculum plays a significant role in the regulation of epileptic activity. Lactate acts as a neuroprotective agent against many conditions that cause brain damage. During epileptic seizures, lactate formation reaches up to ~6 mmol/L in the brain. We investigated the effect of lactate on subicular pyramidal neurons after induction of epileptiform activity using 4‐aminopyridine (4‐AP‐0Mg2+) in an in vitro epilepsy model in rats. The signaling mechanism associated with the suppression of epileptiform discharges by lactate was also investigated. Methods We used patch clamp electrophysiology recordings on rat subicular neurons of acute hippocampal slices. Immunohistochemistry was used for demonstrating the expression of hydroxycarboxylic acid receptor 1 (HCA1) in the subiculum. Results Our study showed that application of 6 mmol/L lactate after induction of epileptiform activity reduced spike frequency (control 2.5 ± 1.23 Hz vs lactate 1.01 ± 0.91 Hz, P = .049) and hyperpolarized the subicular neurons (control −51.8 ± 1.9 mV vs lactate −57.2 ± 3.56 mV, P = .002) in whole cell patch‐clamp experiments. After confirming the expression of HCA1 in subicular neurons, we demonstrated that lactate‐mediated effect occurs via HCA1 by using its specific agonist. All values are mean ±SD. Electrophysiological recordings revealed the involvement of Gβγ and intracellular cAMP in the lactate‐induced effect. Furthermore, current‐clamp and voltage‐clamp experiments showed that the G protein–coupled inwardly rectifying potassium (GIRK) channel blocker tertiapin‐Q, negated the lactate‐induced inhibitory effect, which confirmed that lactate application results in outward GIRK current. Significance Our finding points toward the potential role of lactate as an anticonvulsant by showing lactate‐induced suppression of epileptiform activity in subicular neurons. The study gives a different insight by suggesting importance of endogenous metabolite and associated signaling factors, which can aid in improving the present therapeutic approach for treating epilepsy.