Changes in brain polyribosomes following an electro-convulsive seizure

Enhanced development of morphine tolerance in rats treated with 2-deoxy-D-galactose

Rats treated subcutaneously for 6 days with morphine developed a weak tolerance which was characterized by a decrease in the analgesic action of the opioid. Under those experimental conditions a simultaneous intracerebroventricular application of 2-deoxy-D-galactose enhanced development of morphine tolerance, while other deoxy-sugars like 2-deoxy-D-glucose and 6-deoxy-D-galactose were ineffective. In contrast, no influence of 2-deoxy-D-galactose on a more enhanced morphine tolerance after a 11-day pretreatment with morphine was found. The results are discussed in the light of a rather specific interference of 2-deoxy-D-galactose with neuronal glycoprotein processing and related cellular mechanism underlying adaptive processes involved in the development of morphine tolerance.

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.

The penetration of phenobarbital in generalized and focal penicillin-induced epileptic brain of the cat

The penetration of phenobarbital (PB) into cerebral tissue was determined in cats rendered epileptic by parenteral penicillin and in cats with focal penicillin-induced epilepsy. The results were compared with those from normal controls. In both kinds of experimental models of epilepsy, PB penetration was impaired, although a gradual and progressive accumulation of the drug in the brain tissue was observed in all three groups of cats (binding occurring from time 30 min on). Similar to the events with other substances, such as carbamazepine, the prolonged epileptic activity may have contributed to the impaired penetration of PB, because of severe metabolic alterations secondary to seizures. The present data confirm previous reports indicating that epileptic seizures alter the pharmacokinetics of drugs.

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.

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.

Effect of electroconvulsive shock on polysomes of rabbit brain, liver and kidney

Following electroshock treatment of the rabbit, polysomes have been found to disaggregate in the liver and kidney to an extent comparable with disaggregation in the cerebral cortex. After a single electroconvulsive shock, the process of polysomal disaggregation in the former two organs reaches maximum values at 10 and 60 min, but returns to control values at intermediate times. In the cerebral cortex the shift to control values observed at 20 min is not statistically significant.

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.

Electroshock effects on brain protein synthesis: relation to brain seizures and retrograde amnesia

The effects of electroshock on brain seizure activity and brain protein synthesis were studied in male mice. A significant but short-lasting inhibition of brain protein synthesis and an increase in the amount of free leucine were produced by electroshock at intensities above the brain seizure threshold. Electroshock at intensities below the brain seizure threshold did not affect brain protein synthesis.