Amygdala Kindling Induces Changes in Emotional Behavior of SLOW and FAST Rats
Abstract number :
2.065
Submission category :
Year :
2001
Submission ID :
2804
Source :
www.aesnet.org
Presentation date :
12/1/2001 12:00:00 AM
Published date :
Dec 1, 2001, 06:00 AM
Authors :
S. Schmadel, M.Sc., Dept. of Pharmacology, Toxicology & Pharmacy, School of Veterinary Medicine, Hannover, Germany; D.C. McIntyre, Ph.D., Dept. of Psychology, Carleton University, Ottawa, ON, Canada; U. Ebert, Ph.D., Dept. of Pharmacology, Toxicology & Ph
RATIONALE: Psychiatric diseases like anxiety and depression are common in people with limbic epilepsy. Amygdala-kindling in the rat is an appropriate animal model of limbic epilepsy which allows to study seizure-induced anxiety and depression. We used SLOW and FAST rats for studying kindling-induced changes in emotional behavior. These rat strains are based on a Wistar x Long Evans breeding that were selected for different susceptibility to kindling acquisition. Beside the difference in kindling SLOW and FAST rats also respond differently in tests of emotional behavior which is thought to arise from differences in the expression of the GABA[sub]A[/sub]-receptor subunits (Poulter et al., J. Neurosci. 1999; 19: 4654-61).
METHODS: Female SLOW and FAST rats (n=17, each) were stereotaxically implanted with a bipolar chronic stimulation/recording electrode into the right basolateral amygdala. After one week the emotional behavior of the rats was observed in tests for anxiety (open field, elevated plus-maze) and in a test for depression (forced swimming). Then the rats were daily stimulated via the amygdala (1 ms pulses at initial seizure threshold, 50 Hz for 1 s) until full kindling acquisition, i.e. 6 generalized seizures with loss of righting reflex. One week after the last stimulation the rats[ssquote] behavior was again observed in the same tests.
RESULTS: Before kindling there were no differences between SLOW and FAST rats in the percentage of entries in inner fields of the open field and open arms of the elevated plus-maze. These parameters were reduced after kindling in SLOW rats. The FAST rats only showed a reduction of the percentage of entries in inner fields. After kindling the SLOW rats showed significantly less entries in inner fields and open arms than the FAST rats.
In the forced swimming test in which passive floating during a 5min test is considered as indicator of depressive behavior, the duration of immobility before and after kindling was much longer in SLOW rats (95[plusminus]8s and 120[plusminus]14s) than in FAST rats (7[plusminus]3s and 18[plusminus]5s). Both rat strains showed a longer immobility after kindling than before kindling which was significant in FAST rats.
CONCLUSIONS: These data indicate that epileptogenesis during amygdala kindling increases anxiety. In SLOW rats which needed more stimulations for kindling acquisition, this increase was much stronger than in FAST rats. Compared to FAST rats the SLOW rats showed more depressive behavior, even before kindling. Amygdala-kindling seems to increase depression, especially in the FAST rats which showed little depressive behavior before kindling. Our data substantiate that limbic epileptogenesis by amygdala kindling increases parameters of anxiety and depression in rats and may thus serve as a model of epilepsy-induced changes in emotional behavior.