Histochemistry of Trauma After Electrode Implantation and Stimulation in the Hippocampus

Abstract

Electrodes were implanted into the rat hippocampus in both hemispheres for increasing periods of up to 60 days, and the effects of trauma and electrical stimulation of enzymes controlling cell metabolism in the region of implantation were examined and assessed in relation to studies on humans. In the unstimulated hippocampus as a control, enzyme changes were mainly confined to a narrow area of tissue damage surrounding the electrode. The enzyme changes in response to trauma varied widely; some enzymes controlling tissue respiration showed early and rapid changes, increasing in hyperactive, swollen glial cells and vascular endothelium and decreasing in nerve cells and neuropile. Acid phosphatase activity also increased rapidly in glial cells; other phosphate-releasing enzymes increased more gradually with time. A turning point in these chages was apparent between 25 and 40 days, followed by a reversion to more normal levels at 60 days. Electrical stimulation of the hippocampus in the contralateral hemisphere produced no detectable enzyme changes from those of the unstimulated hippocampus.

Afterdischarge threshold reduction in the kindling model of epilepsy

“…perse, has been shown in several reports to induce histological (Robinson et al, 1975), behavioural (e.g. Hertz et al, 1974).…”

“…Benattia et al, 1992;Ashton et al, 1980) changes. Robinson et al (1975). for instance, found enzyme changes, mainly confined to a narrow area of tissue damage surrounding the electrode tract.…”

“…1992;Aston et al, 1980) changes. These may enhance neuronal excitability, since both Blackwood It is particularly interesting to note the time course of the enzyme changes found by Robinson et al (1975). Enzymes responsible for cellular respiration showed early and rapid changes, increasing in glial cells and endothelium.…”

“…electrode implantation has been shown to induce significant histological (Robinson et al, 1975), and neurochemical (Benattia et al. 1992;Aston et al, 1980) changes.…”

“…The histological findings (e.g. Robinson et al 1975) of changes in enzymes around the electrode tract should be confirrned and extended. The importance of these rnight be tested in experiments which rnanipulated these systems pharmacologically and rnonitored effects on ADT.…”