This review is directed at understanding how neuronal death occurs in two distinct insults, global ischemia and focal ischemia. These are the two principal rodent models for human disease. Cell dea...

Ischemic Cell Death in Brain Neurons

Selective vulnerability of the hippocampus in brain ischemia.

Anisomycin, an inhibitor of protein synthesis, blocks late phases of LTP phenomena in the hippocampal CA1 region in vitro.

The regulation and modulation of pH in the nervous system

Nitric oxide: A radical neurotransmitter in the central nervous system

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.

https://www.jneurosci.org/content/jneuro/4/3/793.full.pdf

An in vitro model of ischemia: metabolic and electrical alterations in the hippocampal slice

The brain slice preparation has been used in a wide variety of investigations since its development in the 1930s by Quastel and by Elliot (Elliot and Wolfe, 1962). Prior to the 1970s, most of this work centered on slice metabolism, with a particular focus on the metabolic consequences of electrical activity (McIlwain and Bachelard, 1971). Although these studies were fundamental to the whole development of the brain slice as a useful preparation, they had a serious drawback in that normal electrophysiological responses could not be obtained from these cortical preparations. Thus, electrical activity was mimicked by profound membrane depolarizations, produced either by high-frequency electrical stimulation or by large changes in extracellular K+ concentrations. More recently, the development of the olfactory and the hippocampal slice preparations (Yamamoto and Kurokawa, 1970; Skrede and Westgaard, 1971) has opened the door to much more sophisticated studies of the relationship between neural activity and energy metabolism than was possible with the previous cortical slice preparation. Thus, it is now possible to correlate metabolic and electrophysiological changes in different conditions and thereby determine mechanisms by which neural transmission affects metabolism and vice-versa (Yamamoto and Kurokawa, 1970).

Energy Metabolism and Brain Slice Function

Hippocampal slices were prepared under three conditions: (1) in medium containing glucose and oxygen at 4 degrees C; (2) as in (1), but at 37 degrees C; (3) in medium devoid of glucose and oxygen at 37 degrees C. The rates of recovery to roughly steady-state levels and through 8 h of incubation were monitored for energy metabolite levels and related parameters. In vitro stable values are compared with in situ hippocampal levels. Regardless of the conditions under which slices were prepared, metabolite levels required up to 3 h to stabilize, and these levels were maintained or improved through 8 h of incubation. Further, the maximal concentrations of metabolites were independent of the conditions of slice preparation. Total adenylates and total creatine levels reached 55% of those in vivo. Lactate decreased from the decapitation-induced high levels, but stabilized at concentrations about twice those in rapidly frozen brain. Cyclic AMP and cyclic GMP exhibited peak levels at 30 min of incubation, and cyclic GMP remained elevated for 3 h. Although all three methods of slice preparation resulted in similar metabolite profiles on incubation, the initial decreases in high energy phosphates were delayed by chilling. Most striking, the slices prepared in the absence of glucose and oxygen exhibited much smaller orthodromic evoked potentials in the dentate gyrus. The presence of glucose and oxygen during preparation of the slices appears to be critical to the electrophysiological response of the tissue.

Tim S. Whittingham

Papers

An in vitro model of ischemia: metabolic and electrical alterations in the hippocampal slice

Energy Metabolism and Brain Slice Function

Metabolic stability of hippocampal slice preparations during prolonged incubation