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

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.