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METABOLIC RESPONSE TO FOCAL PENICILLIN SEIZURES IN RAT: SPIKE DISCHARGE VS. AFTERDISCHARGE 1
Author(s) -
Collins R. C.
Publication year - 1976
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1976.tb02632.x
Subject(s) - penicillin , cortex (anatomy) , chemistry , epilepsy , anesthesia , endocrinology , medicine , neuroscience , biology , biochemistry , antibiotics
– The correlations among clinical events, electrocorticogram, histology, size of focus, and biochemical changes were examined in a model of focal penicillin seizures in rats. Ten units of penicillin injected into the motor cortex were found to be the threshold dose for producing repetitive spike discharges. These were associated with synchronous contralateral muscle jerks which reached a peak intensity in 10 min and fell off rapidly in 45–90 min. The half‐life of penicillin in the cortex was 15 min, with little diffusion from the site of injection. The size of the metabolic focus was determined by autoradiography with [2‐ 14 C]deoxyglucose and was 6.5 times larger than the diffusion of penicillin. Increased glucose utilization appeared in the focus and in cortical columns in the contralateral homo‐typic cortex. Thirty times more penicillin (>300 units) was required to produce spikes with afterdischarge than to product spikes alone. Afterdischarges correlated with contralateral tonic‐clonic seizures and occurred only after 1 h of exposure to penicillin. These lasted 10‐45 s each and recurred over 3 to 4h. The size of the metabolic focus determined by [2‐ 14 C]deoxyglucose during afterdischarges was 4.6 times larger than the focus exhibiting spike discharges alone. Tissue substrates were measured in the seizure focus, homotypic ‘mirror’ cortex, and cortex remote from the focus in paralyzed ventilated animals. During repetitive spike discharge there was a fall in high energy compounds in the focus (phosphocreatine, 4.91 → 4.24 mmol/kg; ATP, 2.62 → 2.17 mmol/kg) and a rise in lactate (1.41 → 2.79 mmol/kg). Changes were similar but less intense in ‘mirror’ and remote cortex. During spikes with afterdischarge, changes in high energy compounds in the focus were of a similar magnitude (phosphocreatine, 4.91 → 3.86 mmol/kg; ATP, 2.62 → 2.46 mmol/kg) but there was a greater rise in lactate (1.41 → 6.32 mmol/kg) and a fall in glucose (2.38 → 1.81 mmol/kg). In contrast, changes in ‘mirror’ and remote cortex during afterdischarges showed an increase in high‐energy compounds.