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1

Effects of conditioned and predictive stimuli on the fly-away escape response in a two-way shuttle box

100%

Savonenko A. V., Zielinski K.

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vol. 58

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issue 4

321

EN

A strong tendency not to return to the previously shocked compartment of a shuttle box was proposed as the main factor retarding two-way avoidance learning (1). It has been shown that the fly-away, rapid escape from an electrified grid, a species-specific defensive reaction of the rat, was observed at the very beginning of avoidance training. Subsequently latencies of the escape response increased, reflecting the conflict situation (2). Here, the modulatory role of a darkness (D) stimulus on the fly-away escape response is studied. Three groups each of 25 experimentally naive male rats were trained under unsignalled escape (Esc), signalled escape (Esc_D), or avoidance (Av_D) procedures. Only shock was presented in Esc, compound shock and darkness in Esc_D, and darkness preceded for 5 s and then accompanied shock in Av_D. The nominal 1.6-mA scrambled pulsed DC shock (50 Hz pulse rate) on the grid floor could be terminated (escaped) by running to the opposite compartment or prevented (avoided) by the same response during the signal-shock interval. The first escape latency was shortest in the Esc_D and longest in Av_D groups (P<0.05, Kolmogorov-Smirnov test; Fig. 1A). Simultaneous presentation of D and shock, presumably enhanced the fly-away escape response because of the higher energizing role of a compound. In contrast, the initial presentation of D in the delayed CS-US contingency may elicit an orienting reflex which interferes with the fly-away reaction. The gradual dissipation of group differences with continued presentation of the stimuli (Fig. 1B) supports this conclusion. During the first 10 trials there were no reliable changes in escape latencies in groups Esc_D or Esc. In contrast, curvilinear changes were revealed in group Av_D: the escape latency on trial 1 was longer than on trials 2, 5, and 6, whereas the escape latency on trials 5 and 6 were shorter than on each of trials 8, 9, and 10 (Kolmogorov-Smirnov test, Ps<0.05). The mean frequency of avoidance responses during these trials was small (0.024/trial). An even earlier increase in escape latency using the avoidance procedure was found with a more salient warning signal (3). Thus, differing from these escape procedures, the avoidance procedure induced the lengthening of escape latencies as early as the first 10 trials of training.

2

Involvement of the lateral and dorsolateral amygdala in conditioned stimulus modality dependent two-way avoidance performance

75%

Werka T.

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issue 2

131-147

EN

Post-lesion learning and performance of shuttle-box avoidance and subsequent transfer to two warning signals (CSs) of different modality were investigated in 27 rats subjected either to a sham lesion (Group NORM), electrolytic injuries of the lateral amygdaloid nucleus (Group LAT), or combined lesions of the amygdalostriatal transition area and dorsolateral amygdala (Group D-LAT). All groups were divided into two subgroups according to warning signal sequences. In the first subgroup (D-DN-N sequence) the subjects were initially trained with the visual CS (darkness - D), then transferred to the more salient visual and auditory compound CS (darkness and noise - DN), and finally to the auditory CS alone (noise - N). The opposite arrangement of the CSs (N-ND-D sequence) was employed in the second subgroup. A small interference with shuttle-box learning, and no transfer deficit were seen in Group LAT, whereas D-LAT rats showed dramatically slow and inconsistent acquisition of avoidance responding followed by rapid weakening of performance during the training. In contrast to controls, in both lesioned groups avoidance and intertrial responding (ITR) were independent of the CS modality changes. The results indicate differential involvement of the lateral, and also of the dorsolateral amygdala, and amygdalostriatal transition area in CS processing, as well as in the mechanisms related to consolidation of the associations created during avoidance training.

3

Participation of different 5-HT receptors in the memory process in rats and its modulation by the serotonin depletor p-chlorophenylalanine

63%

Petkov V. D., Belcheva S., Konstantinova E., Kehayov R.

Acta Neurobiologiae Experimentalis

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1995

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vol. 55

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issue 4

243-252

Refine search results

3 Acta Neurobiologiae Experimentalis

2 1998

1 1995

1 Belcheva S.

1 Kehayov R.

1 Konstantinova E.

1 Petkov V. D.

1 Savonenko A. V.

1 Werka T.

1 Zielinski K.

Effects of conditioned and predictive stimuli on the fly-away escape response in a two-way shuttle box

Involvement of the lateral and dorsolateral amygdala in conditioned stimulus modality dependent two-way avoidance performance

Participation of different 5-HT receptors in the memory process in rats and its modulation by the serotonin depletor p-chlorophenylalanine