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4 Acta Neurobiologiae Experimentalis

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Sex and strain differences of acoustic startle reaction development in adolescent albino Wistar and hooded rats

100%

Blaszczyk J. , Tajchert K.

1996

tom 56

nr 4

919-925

Acoustic startle responses (ASR) were studied in 12 young Wistar albino and in 15 hooded rats of both genders. The six week old animals were first exposed to a 6.9 kHz tone pair of 2 ms pulses of 120 db intensity with the inter-stimulus interval (ISI) between 2 and 11 ms. ASR amplitudes and latencies as a function of the ISI, animal strain and gender were recorded and analyzed for ten consecutive weeks. No differences in the ASR amplitude between Wistar and hooded rats were found. ASR amplitude increased during the experimental period and followed body weight increase. Signiflcant differences were also observed between male and female rats in their startle responses to acoustic stimuli. Generally, male subjects responded with a greater ASR amplitude than females, and the changes may be attributed to the difference in neuromuscular development between genders. This experiment sets a background for further developmental studies

Effect of acoustic stimulus characteristics on the startle response in hooded rats

80%

Blaszczyk J. W. , Tajchert K.

tom 57

nr 4

315-321

The acoustic startle response (ASR) depends on stimulus parameters such as duration, intensity and particularly on the stimulus rise time. The aim of our study was to determine to what extent the ASR parameters are affected by the spectral characteristics of the stimulus. Therefore, in this experiment the amplitude and the latency of the acoustic startle reflex were assessed for a fixed pulse duration and for a variety of stimulus frequencies ranging between 3 and 23 kHz. The ASRs were studied in 11 adult hooded rats exposed to 2 ms (120 dB SPL) tone pulses of different frequencies presented in random order, with or without 70 dB white noise background. Statistical analysis of the data revealed significant differences between ASR amplitudes for different frequencies. In our experimental situation the rats responded more readily to a low frequency stimulus. The startle amplitude decreased with tonal frequencies and distinguishable difference were seen for 3, 7, and 10 kHz pulses. However, such differences were not readily observed for higher frequencies i.e. 15, 20, 23 kHz. The same pattern of differences was observed when the acoustic stimulus was presented with the white noise background. The observed differences may be attributed, firstly, to a spectral characteristic of the stimulus and thus to an audibility in rats and secondly to a behavioral meaning of a stimulus of a different frequency. cy.

Effect of nonaversive and aversive stimulations in infancy on the acoustic startle response in adult rats

80%

Blaszczyk J. W. , Tajchert K. , Werka T.

1999

tom 59

nr 1

9-14

Two groups, each consisting of 8 three-week-old rat pups, were exposed to different behavioral treatments with the aim to determine how the experimental manipulation influenced their adult emotional reactivity. Every day for two weeks the pups from the first group received 15 min of handling whereas the animals from the second group were exposed to various aversive stimuli, differing each day. Following these manipulations, after a 5-day break the acoustic startle response (ASR) was measured in all animals and the testing was repeated after another four weeks. Statistical analysis of the data revealed significant differences between g<->roups in the ASR parameters. Surprisingly, in the test which directly followed the treatment the mean ASR amplitudes were similar in both g<->roups. Highly significant differences, however, were observed in the ASR amplitude four weeks later. The rats from the handling group responded with greater amplitudes. The latency of the ASR was significantly shorter in the nonaversive group compared with the second group exposed to aversive stimuli. The results suggest that early exposure to aversive stimulation significantly decreases rats emotional reactivity whereas nonaversive and impoverished stimulation clearly elevates arousal levels when the animal is placed in a novel situation.

Changes of the acoustic startle reflex in rats with radiation-induced hippocampal lesion

80%

Blaszczyk J. W. , Walasek G. , Woznicka A. , Seress L.

nr 3

171-176

The main question of the study was: to what extent does a neonatal radiation-induced hippocampal lesion lead to emotional changes in adulthood? Acoustic startle response (ASR) was studied in two groups of adult rats. The rats from the first group (14 animals) were exposed to neonatal x-ray irradiation. Their ASR were compared with those from the 10 intact rats that formed a control group. The ASR was tested during two sessions with different illumination of the acoustic chamber. During the first session the rats were tested in the darkness while during the second test the acoustic chamber was illuminated with a 15 W bulb. Irradiation resulted in a significant reduction of granule cells of the hippocampus (about 55%). The lesion resulted in emotional and behavioral changes evidenced by modification of the ASR. The irradiated rats exhibited a significantly increased amplitude of the startle response. In contrast to the light condition, the darkness context caused a decline of the ASR amplitude in the control group and failed to elicit significant changes in the lesioned animals. The results support the hypothesis that hippocampal lesions disrupt motor inhibition.