Long-term effect of electroshock treatment on the entry of calcium into the cerebroventricular fluid in the rat

Alterations by antidepressants of cerebrospinal fluid formation and calcium distribution dynamics in the intact rat brain

The formation of cerebrospinal fluid (CSF) after chronic treatment with imipramine (IMI), lithium (Li), or electroshock (EST) was studied in urethane-anesthetized rats by ventricular-cisternal perfusion with 14C-inulin. Effects of these treatments on the removal of 45Ca from the cerebroventricular perfusate were also studied. The mean value for CSF formation in control rats was 2.6 +/- 0.2 microliters/min. EST and IMI both increased CSF formation significantly (+38% and +19%, respectively). Li caused a significant decrease (-19%). Endogenous removal of 45Ca was by bulk CSF absorption to blood and by uptake to brain. In control animals, the uptake by brain accounted for 42% of the total endogenous removal at the steady state. Each of the applied treatments resulted in a significant decrease in the fraction of 45Ca taken up by the brain (EST 26%, IMI 33%, Li 29%). Thus, although chronic EST or IMI resulted in an effect opposite to that obtained by Li on CSF formation, all three treatments appear to act similarly in reducing calcium passage from the cerebroventricular compartment to brain tissue.

Contributions of basic neurochemistry towards a novel concept of epilepsy

Epilepsy is an ancient disorder which treatment over the centuries has been guided by preconceptions regarding its origin. The major improvements in epilepsy management came following the discovery of the EEG and the development of seizure suppressing agents. These advances in diagnosis and anticonvulsant therapy have further ingrained the conviction that epilepsy is a disease of neurons. Evidence presented here is intended to support a different point of view which suggests that the metabolic modifications in epileptogenic tissue denote subtle alterations in the anatomical and biochemical relationship between neurons and their glial envelopes. As a result the extracellular environment of these cells contain higher than normal levels of glutamic acid. This creates an unnatural functional connectivity between neurons so that they establish abnormal synchronous activity between them and become hyperexcitable due to the depolarizing milieu. To compensate for these biochemical changes it is suggested that some thought might be given to epilepsy management by metabolic manipulation. The measures should be directed specifically towards improving the ability of glia to remove glutamic acid from the extracellular milieu. Two obvious possibilities are to enhance glial glutamine synthesis and to improve the interstitial "wash-out" of glutamic acid in epileptogenic epicenters. Such a therapy would anticipate to gradually diminish seizure incidence and susceptibility without, however, having a direct action on convulsive episodes per se. The approach must be considered an adjunct to current epilepsy treatment and not a substitute for the use of anticonvulsants.