A physiclogical difference in the hippocampus of rats with a low inborn learning ability

✍ Scribed by Iván Izquierdo; Otto A. Orsingher

• Publisher: Springer
• Year: 1972
• Tongue: English
• Weight: 647 KB
• Volume: 23
• Category: Article
• ISSN: 0033-3158
• DOI: 10.1007/bf00406741

✦ Synopsis

Rats with a low ability to learn conditioned avoidance responses in a shuttle-box were in-bred. After five or six generations, a fairly homogeneous population was obtained consisting of bad learners both in the shuttle-box and in a Lashley III maze. When the hippocampus of these bad-learner rats was perfused with high potassium solutions, it was observed that more stimuli were needed, under each potassium concentration, in order to elicit a seizure, than in normal animals. This was apparently the result of a lower release of potassium per stimulus into the extracellular space, in as much as other possibilities (low sensitivity to the epileptogenie effect of potassium, large extracellular space, high Na-K-~g-ATPase activity) were excluded. This reduced potassium release by stimulation in the hippocampus of bad-learner rats was not due to a lower potassium gradient across cell membranes, and therefore, could in principle be attributed to a defect in the property of local neural membranes (pre-and/or postsynaptie) to increase potassium conductance when stimulated.

The present data fit with the hypothesis advanced previously, that the hippocampus plays a role in learning through heterosynaptic interactions mediated by the release, and subsequent accumulation of potassium.