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The kindling effect as a part or full-term laboratory exercise in physiological psychology courses
Abstract
Use of the kindling effect for laboratory work in physiological psychology courses is suggested. This effect can involve a number of learning experiences: making bipolar electrodes, implanting these electrodes in the amygdala, stimulating animals and observing behavior for weeks or months, doing histological analyses. A simple kindling experiment for a full term is described.
Various solvents and chromatographic plates were used in thin layer chromatography in an attempt to determine unique patterns resulting during the kindling process. The patterns were the same for nonstimulated controls and for rats at various points of behavioral changes.
Eighteen experiments pairing the transfer experiment with the kindling paradigm were conducted. The brain homogenate supernatant from rats kindled to clonic convulsions was injected intraperitoneally into naive recipients. Similar material from nonkindled rats was injected into other naive recipients. One, two, two and one-half, and three brain amounts were used. Recipients receiving supernatant from kindled animals were retarded significantly in the development of clonic convulsions for all brain amounts. No clear retardation effect was obtained if the supernatant was injected intracerebrally or if the recipients had reached the convulsion stage.
Previous experiments indicated that the development of clonic convulsions could be retarded by intraperitoneal injections of brain homogenate supernatant from male Wistar rats which had previously convulsed via amygdaloid electrical stimulation when naive recipients were used. Two further experiments were conducted with recipients which had reached the convulsion stage. In each of these experiments there was no indication of a retardation or suppressive effect.
Animals subjected periodically to low-intensity electrical stimulation unilaterally to the amygdala or some other brain sites gradually develop automatic behaviors which culminate eventually in convulsions. Characteristic brain wave patterns accompany these behavioral changes. A 60-Hz sine wave with a 24-h interval provides the most optimum condition of stimulation. This kindling effect shows some characteristics similar to learning events, viz, relatively permanent changes, positive and negative transfer effects, involvement of limbic system. The results suggest that two factors are involved in the kindling process: a long-term effect of positive nature (probably due to modified neural circuitry) and a short-term “aftereffect” of negative nature.
Five experiments were conducted in which donor rats were kindled to the clonic-convulsion stage, sacrificed, and their brains removed. The brain was homogenized, and the supernatant fraction was injected intraperitoneally into recipient experimental rats, who then were subjected to the kindling procedure. Control donors which received no stimulation were included. When the injection involved two or more brain amounts, a retarding effect tended to occur with the experimentals. If only one brain amount was used for the injection, no change resulted in the kindling rate of these recipients. This interanimal negative-transfer effect appears to be similar to the intraanimal negative-transfer effect reported by Mclntyre and Goddard.
Repeated electrical stimulation in the limbic system causes permanent changes in the susceptibility to epileptiform afterdischarge and motor seizure; the present study examined the involvement of cholinergic and catecholaminergic neural circuits in the mechanism underlying these changes. The cholinergic blocking agent atropine retarded the rate of seizure development without altering the local afterdischarge threshold. Atropine appeared to suppress propagation of epileptiform afterdischarge to other structures within the limbic system. By contrast, attenuation of catecholaminergic activity by intraperitoneal injections of reserpine or intraventricular applications of 6-hydroxydopamine facilitated seizure development, while stress, which elevates catecholaminergic activity, retarded seizure development. These studies suggest that cholinergic circuits in the limbic system play an important role in propagating epileptiform discharge within the limbic system, and raise the possibility that noradrenergic or dopaminergic circuits act in antagonism to these cholinergic “seizure circuits”.
Brief bursts of nonpolarizing electrical brain stimulation were presented once each day at constant intensity. At first the stimulation had little effect on behavior and did not cause electrographic afterdischarge. With repetition the response to stimulation progressively changed to include localized seizure discharge, behavioral automatisms and, eventually, bilateral clonic convulsions. Thereafter, the animal responded to each daily burst of stimulation with a complete convulsion. The effect was obtained from bipolar stimulation of loci associated with the limbic system, but not from stimulation of many other regions of the brain. Parametric studies and control observations revealed that the effect was due to electrical activation and not to tissue damage, poison, edema, or gliosis. The changes in brain function were shown to be both permanent and trans-synaptic in nature. Massed-trial stimulation, with short inter-burst intervals, rarely led to convulsions. The number of stimulation trials necessary to elicit the first convulsion decreased as the interval between trials approached 24 hours. Further increase in the inter-trial interval had little effect on the number of trials to first convulsion. High-intensity stimulation studies revealed that the development of convulsions was not based simply on threshold reduction, but involved complex reorganization of function. Experiments with two electrodes in separate parts of the limbic system revealed that previously established convulsions could facilitate the establishment of a second convulsive focus, but that the establishment of this second convulsive focus partially suppressed the otherwise permanent convulsive properties of the original focus.
Interanimal negative transfer of the kindling eflL'Ct. Physiological Psychology
- Gaito
- S T Gaito
GAITO. J" & GAITO, S. T. Interanimal negative transfer of the
kindling eflL'Ct. Physiological Psychology. 1974. 2. 379-382.
Experimental neuropsychology
- B L Hart
San Francisco: FrL'Cman. 1%9. (Received for publication June I\
- Hart B L Experimelltal Lieuropsychology
HART. B. L. Experimelltal lIeuropsychology. San Francisco:
FrL'Cman. 1%9.
(Received for publication June I\. 1975;
accepted June 17.1975.)