Effect of experimental status epilepticus on the pattern of RNA synthesis in cerebral cortex

Amyloid precursor protein mRNA encoding the Kunitz protease inhibitor domain is increased by kainic acid-induced seizures in rat hippocampus

A 168-nucleotide exon, found in alternatively spliced amyloid precursor protein (APP) mRNAs, encodes a Kunitz protease inhibitor (KPI) domain. Kainic acid (ip) caused a selective increase of KPI mRNA in rat hippocampus. By in situ hybridization, KPI mRNA was induced in the neuronal layers of the hippocampus 11-12 h after the onset of kainate-induced seizures. The kainate-induced elevation of the KPI-containing APP-770 mRNA was blocked by pretreatment with the anticonvulsant pentobarbital. These data suggest that kainate-induced seizures cause alterations in APP RNA stability and/or processing in rat hippocampal neurons.

Alterations in polyadenylic acid-containing messenger RNA synthesis of brain polysomes after seizures of seizure-susceptible E1 mice

The effect of seizures on synthesis of the polyadenylic acid (poly(A]-containing messenger RNA (mRNA) isolated from brain polysomes in a genetically seizure-susceptible E1 mouse was studied in vivo. The seizure in the E1 mice was induced by tossed-up stimulation. Immediately after the seizure ceased, the labeled orotic acid was injected into the brain. The incorporation rates of labeled orotic acid into poly(A)-containing mRNA isolated from polysomes are represented as the specific radioactivity (SR) (dpm/mg RNA) and the relative specific radioactivity (RSR) (dpm/mg RNA/dpm/mumoles of acid soluble uridine-5'-monophosphate (UMP]. Both the rates were reduced to 70% in SR and 65% in RSR at 1 h after the seizures. This reduction was gradually recovered to the level of interictal E1 mice at 6 h. The seizure-induced alterations are not attributable to the difference in the uridine nucleotide pool because the SR of UMP was not significantly affected by the seizure. The peak of labeled poly(A)-containing mRNA by analysis of gel electrophoresis displaced towards a lower molecular weight at 1 h after the seizures. The RNA showed a higher ratio of AMP and UMP per GMP and CMP in nucleotide composition, implying that this RNA is identical with DNA. These results suggest that the temporary decrease found in cytoplasmic mRNA synthesis induced by the seizures of E1 mice appears to be a result of impaired transcriptional processes in heterogeneous nuclear RNA synthesis and that the smaller mRNA coding for protein associated with seizures is newly synthesized during the postictal period.

Effect of convulsions of the synthesis of heterogeneous nuclear RNA associated with polyadenylate and oligoadenylate sequences from El mouse brain as a convulsive strain

Animals from the El (susceptible to seizures) and ddy (nonsusceptible) mouse strains were subjected to vestibular stimulation by tossing. After convulsions in the El mice, both the stimulated El mice and ddY mice were intracranially injected with [14C]- and [3H]adenosine, respectively. In the control experiment, nonstimulated El and ddY mice received radioactive adenosines in the same manner. The rate of incorporation of adenosine into brain nuclear RNA, expressed as a percentage of the 3H; 14C ratio, was reduced to an average of 68% at 15 min after convulsions, then increased and reached a control value at 5 h. This reduction in nuclear RNA synthesis was not due to alteration of the adenosine triphosphate pool. Gel electrophoresis of RNA revealed no obvious differences in the labeling distribution between El and ddY mice, but the synthesis of RNA species larger than 35S in heterogeneous nuclear RNA (HnRNA) was impaired in convulsed El mice. Nuclear resistant segments of HnRNA with both T1 RNase and RNase A, were chromatographed with poly(U)-Sepharose followed by urea-polyacrylamide gel electrophoresis. The ologo(A) and poly(A) segments consisted of 29, 19, and 11, and 203, 135, and 69 nucleotides, respectively. The convulsions of El mice reduced the incorporation of radioactive adenosines into oligo(A) and poly(A) segments, suggesting that they inhibited transcription as well as polyadenylation within HnRNA.

Labeling of non poly(A) associated RNA in the rabbit cerebral cortex 24 hours after a single electroconvulsive shock

The labeling pattern of non poly(A) associated (poly(A)-)RNA of rabbit cerebral cortex was studied 24 hr after a single electroconvulsive shock (ECS). The animals were injected subarachnoidally with [3H]uridine and sacrificed 1 hr later. The fractionation pattern of labeled nuclear poly(A)-RNA in the cerebral cortex of ECS treated animals was identical to that of the controls. However, microsomal poly(A)-RNA from the treated animals showed an increased labeling of 18S ribosomal RNA. Also 28S RNA displayed a higher labeling but the effect was not statistically significant. These results indicate a more efficient production of ribosomal RNA in the late post-ECS period which might be in relationship with an increased activity of brain protein synthesis machinery.

Developmental alteration in RNA metabolism of E1 mouse brain

The contents of brain RNA rose rapidly until 14 days after birth and then dropped. They were lower in the E1 than in the non-convulsive mice between 56 and 100 days of life. The contents of acid-soluble UMP and their specific radioactivities, three hours after an intracranial injection of [3 H]-orotic acid, were not different in the same age of E1 and non-convulsive mouse brains. From four to 20 days after birth, the specific and relative specific radioactivities, representing the ratio of brain RNA synthesis, of the E1 mice were lower than those of the non-convulsive strains, while the E1 mice, applying convulsions once a week, exhibited higher values during the periods from 56 to 100 days of age as compared with the non-stimulated E1 or non-convulsive strains.

Long-lasting effects of electroconvulsive shock on the pattern of poly(A)-RNA synthesis in rabbit cerebral cortex

The pattern of poly(A)-associated [poly(A)+] RNA synthesis was studied in rabbit cerebral cortex in the period following a single electroconvulsive shock (ECS). Labeled uridine was injected into the brain 2 and 4 hr after ECS and the animals sacrificed 1 hr later. Total and poly(A)+ RNA were then prepared from cortical nuclei and microsomes and analyzed. The amounts of newly synthesized total and poly(A)+ RNA in nuclei and microsomes appeared to be close to the control. However, the pattern of newly synthesized poly(A)+ nuclear RNA appeared to be still displaced toward the high molecular weights as it was in the early post-ECS period. The result indicates a long-lasting disturbance of brain poly(A)+-RNA metabolism by ECS.

Modification in messenger RNA population synthesized in rabbit cerebral cortex in the recovery period following convulsions

The labeling pattern of microsomal poly(A)-associated messenger RNA was studied in rabbit cerebral cortex during the postconvulsive period. Labeled uridine was injected into the brain 2 hr after a single electroconvulsive shock and the animals sacrificed 1 hr later. Poly(A) RNA was then extracted from cerebral cortex microsomes, and fractionated by gel electrophoresis. The results indicate that the messenger RNA population synthesized in the cortex in the postconvulsive recovery period is clearly different from that synthesized in the normal controls.

EEG-changes during general anaesthesia with enflurane (Efrane) in comparison with ether

The effects of enflurane (efrane) and ether on the cerebral functions were studied by EEG on two similar groups of adult patients. For basic comparison a depth of anaesthesia was chosen which permitted abdominal surgery without the need to administer muscular relaxants. At this level of anaesthesia the typical EEG-changes of paroxysmal type which have been described with enflurane were seen only occasionally. If, however, the depth of anaesthesia was further increased, such EEG-changes indicating increased cerebral excitability were seen more often under enflurane and also appeared under ether anaesthesia. No seizure activity was recorded.