Brain protein synthesis after electroshock

Brain electrical stimulation: kindling and memory aspects

After short introduction in which mile-stones of brain electrical stimulation are mentioned, author discusses kindling as a model of epilepsy and learning. The plastic nature of these two neuronal processes is discussed from the point of view: 1. similarities of these two processes and 2. relation between epileptic discharges (seizures) and learning (memory). The lack of quantitative analysis of afterdischarge duration and its effect on retention is emphasized. Author presents his own study of relation between performance of formed motor avoidance conditioned reflex (CR) and epileptic spontaneous spike activity in hippocampi and duration of afterdischarges (AD) in hippocampi and amygdala in hippocampal kindling in cats. It was shown that spontaneous hippocampal spikes, dissipated over a time, have no effect on performance or retention of the CR. However, there is clear relation between duration of AD and retention of the CR. When duration of the AD was to 15 seconds, correct CRs were obtained in 75% and in 25% the result was negative CR. However, when duration of the AD was longer, the CS presentation between 16-30 sec. resulted in 75% of negative CR and 25% of positive CRs. When the CS was presented during ADs which were longer than 30 sec. almost in all cases the CR was negative, however, in a few instances still possible. Complex effect of brain stimulation are discussed and value of weak stimulation like in kindling technique is emphasized.

Electric shock convulsions in the rabbit and brain cortex GABAA receptor function

The effect of electric shock convulsions (ESC) on the function of brain cortex GABAA receptors has been studied in the rabbit. Three single electroconvulsive shocks (ECS) were given at intervals of 48 hours and the brain cortex was sampled 36 hours after the last shock. The dose-response curve was determined for GABA-stimulated 36Cl-accumulation into brain cortex microsacs. The parameters of the curve (maximal accumulation rate, Ka and Hill coefficient, n) were constant when determined in two different series of experiences. Animals handled in the same way as the animals from the electric shock group but which did not receive the ECSs (sham ECS group) showed similar maximal accumulation rate and Ka. However, the average n coefficient was significantly higher in the electric shock group. Naive animals, taken from their cages just before the sacrifice, showed dose-response curves which varied from one experimental series to another. This last result (confirming previous observations) shows modifications and inconsistencies in the evaluation of GABAA receptor function in stressed handling-naive animals.

Alteration of RNA synthesis in vitro in intact cerebral cortex nuclei induced by convulsions in seizure-susceptible El mice

We examined the effects of convulsive seizures on in vitro RNA synthesis by cerebral cortex nuclei in El mice. The rate of incorporation of [3H]uridine-5'-triphosphate by intact nuclei during seizures was decreased to 47.4% compared with the rate during the interictal period, but gradually recovered. During the 30-min period after onset of seizures, the rate of RNA synthesis was significantly lower in El mice than in identically stimulated ddY mice. Seizures in El mice had no effect on liver RNA synthesis, suggesting that the alteration of RNA polymerase activity is specific to the brain. Analysis of gel electrophoresis of polyadenylated RNA synthesized in the presence of ammonium sulphate revealed a marked decrease in high-molecular weight RNA species 15 min after seizures in El mice compared with the pattern in nonstimulated ddY mice. This shift from high- to low-molecular weight RNA species was not attributable to RNase activity, but it appeared to be related RNA polymerase.

Pattern of labeling of rabbit cerebral cortex soluble proteins 24 hours after a single electroconvulsive shock

The labeling of proteins in the particulate subcellular fractions and in the cell sap was studied in the cerebral cortex of rabbits 24 hours after a single electroconvulsive shock (ECS). To this end the animals were injected with [3H]valine subarachnoidally and sacrificed 30 minutes later. The incorporation of the labeled amino acid into proteins was slightly increased in all subcellular fractions but the increase was significant only for soluble proteins. Referring to the type of soluble polypeptides found in the cortex at this post ECS phase, no modification was found in the SDS electrophoresis pattern of steady state proteins. The fractionation pattern of labeled soluble proteins showed in one third (3 out of 9) of the experiments a remarkable stimulation of the synthesis of two polypeptides (25,000 and 54,000 Dalton MW), which were not labeled in the controls.

Role of hyperthermia in effects of electroconvulsive shock on protein synthesis in the rabbit

The effects of electroconvulsive shock (ECS) on rectal temperature (TR) and on protein synthesis in brain and liver were compared in rabbit, rat, and mouse. Protein synthesis status was assessed using an in vitro amino acid incorporation method which provides information equivalent to polyribosome profiles. In the rabbit, TR rose from 39.5 +/- 0.4 degrees C to 40.4 +/- 0.2 degrees C within 10 min following a single ECS, and significant hyperthermia persisted for at least 60 min. This effect was markedly attenuated in animals housed at 4 degrees C. In vitro protein synthesis activities of rabbit brain and liver preparations were significantly reduced following ECS only in those animals whose TR exceeded 40 degrees C. In the rat, ECS gave rise to a significant hyperthermia, but in no case did TR exceed 40 degrees C, and protein synthesis activity of brain supernatants was not affected. In the mouse, ECS reduced TR and had no effect on in vitro protein synthesis activity. These results demonstrate that the unique sensitivity of protein synthesis in rabbit tissues to electroconvulsive shock is a direct consequence of the hyperthermia that arises following ECS in this species.

Regional impairment of protein synthesis in the rat brain during bicuculline-induced seizures

Protein synthesis was investigated in rats subjected to 30 min of bicuculline-induced seizures using biochemical and autoradiographic techniques. Incorporation studies were performed on freely convulsive animals following systemic administration of either a tracer dose of L-[1-14C]tyrosine or a flooding dose (7.5 mmol/kg) of L-[1-14C]valine. Using a tracer dose, amino acid incorporation was only moderately reduced (forebrain) or slightly enhanced (cerebellum/brainstem and spinal cord) but the specific radioactivity of [14C]tyrosine in the acid-soluble pool was increased 3- to 5-fold in experimental animals. After a flooding dose of [14C]valine the specific activity of the precursor amino acid was similar in control and convulsed animals. Under these conditions incorporation rates in forebrain and cerebellum/brainstem were reduced to 54 and 75%, respectively. Reduction of amino acid incorporation was even more pronounced in extraneural tissues, e.g. liver (6%), intestine (14%) and kidney (15%). Inhibition of protein synthesis in forebrain and cerebellum/brainstem was paralleled by a similar extent of polyribosome disaggregation in these regions (53 adn 78% of controls). In anaesthetized, mechanically ventilated rats, 30 min of seizure activity reduced forebrain polyribosomes to a similar extent (57%). Extraneural (hepatic) protein synthesis was also affected in physiologically controlled rats, but cerebellar polysomes were completely preserved. Autoradiographic studies using 3H-labelled amino acids were carried out to identify nerve cell populations most heavily affected. In freely convulsive rats both tracer dose and pool overloading revealed a similar regional pattern with preferential inhibition of amino acid incorporation in forebrain cortex, thalamus and the pyramidal cell layer of the hippocampus. These sites were also affected in the physiologically controlled animal, but the focal distribution of hippocampal and thalamic neurones with reduced protein synthesis differed from that in freely convulsive rats.

Investigation of the reported protective effect of cycloheximide on memory

Many findings support the hypothesis that formation of long-term memory requires synthesis of proteins in the nervous system close to the time of learning. This hypothesis has been challenged recently by reports that the protein synthesis inhibitor cycloheximide (CYC) injected 2 hr prior to passive avoidance training in mice or rats attenuated the memory impairment induced by a usually amnestic dose of CYC administered 30 min pretraining. To investigate the reports of a "protective" effect of the prior injection, we attempted to replicate them and test their generality. For replication we administered either paired injections of CYC--120 mg/kg 2 hr prior to training and 30 mg/kg 30 min prior to training--or single injections of CYC (either 120 mg/kg or 30 mg/kg) 30 min pretraining and tested for retention of the passive avoidance habit either 1 or 7 days later. No attenuation of amnesia was observed at 1 day tests. Attenuation of amnesia following the double injection of CYC was observed at 7 day tests. When another protein synthesis inhibitor, anisomycin, was used in the same experimental design, there was no "protective" effect; two injections of anisomycin produced greater memory impairment for the passive avoidance habit than did the single low dose. Also, for active avoidance training, two successive injections of CYC caused significantly greater amnesia than did a single dose; this is the opposite of a "protective" effect. We suggest that the reported "protective" effect of CYC on memory is an as yet unexplained phenomenon that does not generalize to other antibiotic drugs and is specific to the passive avoidance task.

Dissociation between epileptic seizures induced by convulsant drugs and alteration in the concentrations of pyridoxal phosphate in rat brain regions

Allylglycine increased the concentration of pyridoxal phosphate in cerebral cortex from 1011.4 +/- 25.0 to 1318.0 +/- 66.3 and decreased it in cerebellum from 1289.0 +/- 49 to 1147.7 +/- 119.4 ng/g wet tissue during the preictal period. Mercaptopropionic acid increased the concentration of pyridoxal phosphate in cerebellum from 1525 +/- 91 to 1985.7 +/- 275 ng/g wet tissue. Similar effects were noted in hippocampus and cerebral cortex. Picrotoxin increased the concentration of pyridoxal phosphate in hippocampus from 938.7 +/- 44 to 1043 +/- 118 but decreased it in cerebral cortex from 1124.52 +/- 124 to 979.4 +/- 15 ng/g wet brain. The effects of strychnine were identical to those of allylglycine. Bicuculline reduced the concentration of pyridoxal phosphate in cerebral cortex from 1184 +/- 61 to 1075.14 +/- 78 ng/g wet brain.

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.

In vivo inhibition of incorporation of [U-14C]glucose into proteins in experimental focal epilepsy

The in vivo incorporation of [14C] from [U-14C]-glucose into rat brain proteins from different cortical areas was examined in three different experimental focal epilepsies: cobalt, freeze-lesions, and tityustoxin. When [U-14C]-glucose was injected intraperitoneally into awake and unrestrained animals with marked signs of epileptic hyperactivity, the inhibition of incorporation of [14C]-amino acids into trichloracetic acid (TCA)-insoluble proteins was highest in the focal (sensorimotor) area when compared with distant regions (approx. 60%), but less when compared with the contralateral (sensorimotor) region (approx. 23%). Greatly decreased incorporation caused by both cobalt and freeze-lesion-induced epilepsies was also observed in the contralateral area when a comparison was made with distant regions (approx. 50%), but there were no significant differences in protein-specific radioactivity between the different distant areas.

Changes in [3H]lysine incorporation into protein in a seizure focus in rat isocortex

A focus of epileptiform discharge was induced in rat isocortex by subpial injection of 5 microliters of 100 mM FeCl3. Control animals were prepared with saline injections. Protein synthesis was estimated by uptake of [3H]lysine and its incorporation into protein at the site of iron injection, in the contralateral homotopic isocortex, and in the midline cerebellum. We found diminished uptake of [3H]lysine into all regions of rat brain in the interictal or nonseizing iron-injected animals, whereas the corrected rate of incorporation of [3H]lysine into protein was not significantly different from control rates. Actively seizing animals showed no inhibition of uptake of [3H]lysine, but [3H]lysine incorporation into protein relative to the uptake was significantly inhibited within the epileptic focus but not in the other areas examined. This decreased incorporation of amino acids into protein parallels that found in animals convulsing after electroshock or pentylenetetrazol injection.

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.

Cytophotometric and morphometric studies of postnatal rat hippocampal neurons and perineuronal gliocytes after electroconvulsive shock

Electroconvulsive shock was evoked by transcorneal electric current (50 Hz, 50 mA; 3 times by 0.2s with 10-min pauses) in 10-day and 20-day old rats. 2 hours after the end of the convulsions, the total cytoplasmic RNA and protein content per cell in CA3 hippocampal neurons has been shown cytospectrophotometrically to increase markedly in 10-day old rats without statistically significant changes in 20-day old animals. No changes in the RNA and protein content were found in perineuronal neuroglia cells in the CA3 hippocampus in both age groups of rats. Morphometric determinations revealed a pronounced augmentation of volumes of the hippocampal neuronal bodies, nuclei, and cytoplasm as well as of nucleo-cytoplasmic ratio in 10-day old rats under effect of electroconvulsive shock. In 20-day old rats, the shock led to less marked increase in volumes of the hippocampal neurons, with no changes in nucleo-cytoplasmic ratio.

Brain noradrenergic responses to training and to amnestic frontal cortex stimulation

Rats were trained in a one-trial inhibitory (passive) avoidance task prior to receiving supraseizure electrical stimulation of frontal cortex, a treatment that results in amnesia. Forebrain and brain stem norepinephrine (NE) concentrations decreased by 23% 10 min after footshock training. Posttraining frontal cortex stimulation resulted in a potentiation of the forebrain NE response (to 31-33% below control values) and in attenuation of the brainstem response (0-5% lower than control values). These results are consistent with previous findings that indicate that good retention performance is predicted by training and treatment conditions that result in approximately a 20% decrease in brain NE content as measured 10 min after training; deviations from this optimal level, presumably reflecting more or less NE release, predict poor retention in comparably trained and treated rats. Thus, memory storage processing appears to be sensitive to many manipulations that alter the endogenous posttraining brain NE response to footshock.

The effect of convulsions induced by flurothyl on ribonucleic acid synthesis in rat cerebral cortex during the recovery phase

The effect of convulsions, induced by flurothyl, on RNA synthesis in purified unfractionated nuclei and the cytoplasm of rat cerebral cortex was studied by using a double-label technique involving injection of [3H]- and [14C]-orotate intracisternally. 2. Intact RNA was extracted in 80% yield by an enzymic method by using a proteinase in the presence of sodium dodecyl sulphate followed by deoxyribonuclease. Electrophoresis on 1.5% polyacrylamide-0.5% agarose gels revealed the presence of giant nuclear RNA of size up to approx. 300X 10(6) daltons and mRNA of maximal mol.wt. 9 X 10(6)-16 X 10(6). 3. Nuclear RNA synthesis was decreased to 27% in the first 15 min after convulsions but rapidly increased, so that at 1 1/2 h it was 124% of the control, and at 6 h 147%. 4. Labelling of cytoplasmic RNA was decreased to 15% at 15 min after convulsions but had not recovered to control values by 6 h. 5. Analysis of radioactive gel patterns and the 3H/14C ratio at six time-points (15 min-6h) showed that the major effect was inhibition of the processing of heterogeneous nuclear RNA resulting in a sharp decline in the export of newly synthesized RNA from the nucleus. 6. Cytoplasmic RNA patterns indicated that specific messengers were synthesized at different times during the recovery of the cell after convulsions.

Retrograde amnesia gradients: effects of direct cortical stimulation

Electrical stimulation was delivered bilaterally to either the anterior or posterior cortex in rats from 0.1 second to 4 hours after a single training trial on an inhibitory avoidance task. As indicated by a retention test given 24 hours later, the length of the retrograde amnesia gradients ranged from 5 seconds to 240 minutes, depending on the brain region stimulated and the intensity of the stimulating current. The stimulation intensity that was threshold for amnesia varied directly with the length of the interval between training and treatment.

Memory traces: experimental separation by cycloheximide and electroconvulsive shock

Mice given cycloheximide or saline were trained with a single trial. Electroconvulsive shock was administered to both groups at various times after training. Cycloheximide led to memory that decayed with time. Cycloheximide plus electroconvulsive shock produced complete amnesia at times when neither treatment alone produced amnesia. Only two types of processes appear to support memory storage in our study.

Modification of memory systems: some neurobiological aspects

The findings of clinical and experimental studies conducted over the past 25 years provide extensive evidence that in both laboratory animals and man memory can be modified by treatments which affect the central nervous system. Patients with head injuries may suffer from retrograde amnesia, a loss of memory for experiences which occur just prior to the onset of the injury. Findings of laboratory studies using animal subjects indicate that retrograde amnesia can be produced by a wide variety of experimental treatments.