[31P]/[1H] Nuclear magnetic resonance study of mitigating effects of GYKI 52466 on kainate-induced metabolic impairment in perfused rat cerebrocortical slices

Abstract

Purpose: Kainic acid (KA) has long been used in experimental animals to induce status epilepticus (SE). A mechanistic implication of this is the association between excitotoxicity and brain damage during or after SE. We evaluated KA-induced metabolic impairment and the potential mitigating effects of GYKI 52466 [1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3- benzodiazepine] in superfused rat cerebral cortical slices. Methods: Interleaved [31P]/[1H] magnetic resonance spectroscopy (MRS) was used to assess energy metabolism, intracellular pH (pH(i)), N-acetyl-L-aspartate (NAA) level, and lactate (Lac) formation before, during, and after a 56-min exposure to 4 mM KA in freshly oxygenated artificial cerebrospinal fluid (oxy-ACSF). Results: In the absence of GYKI 52466 and during the KA exposure, NAA, PCr, and ATP levels were decreased to 91.1 ± 0.8, 62.4 ± 3.9, and 59.1 ± 4.3% of the control, respectively; Lac was increased to 118.2 ± 2.1%, and pH, was reduced from 7.27 ± 0.02 to 7.13 ± 0.02. During 4-h recovery with KA-free ACSF, pH(i) rapidly and Lac gradually recovered, NAA decreased further to 85.5 ± 0.3%, and PCr and ATP showed little recovery. Removal of Mg2+ from ACSF during KA exposure caused a more profound Lac increase (to 147.1 ± 4.0%) during KA exposure and a further NAA decrease (to 80.4 ± 0.5%) during reperfusion, but did not exacerbate PCr, ATP, and pH(i) changes. Inclusion of 100 μM GYKI 52466 during KA exposure significantly improved energy metabolism: the PCr and ATP levels were above 76.6 ± 2.1 and 82.0 ± 2.9% of the control, respectively, during KA exposure and recovered to 101.4 ± 2.4 and 95.0 ± 2.4%, respectively, during reperfusion. NAA level remained at 99.8 ± 0.6% during exposure and decreased only slightly at a later stage of reperfusion. Conclusions: Our finding supports the notion that KA-induced SE causes metabolic disturbance and neuronal injury mainly by overexcitation through non-N-methyl-D-aspartate (NMDA) receptor functions.