Original ArticlesPrepulse inhibition following lesions of the inferior colliculus: prepulse intensity functions
Section snippets
Animals
Experiments were conducted on 27 male adult Wistar rats (Rattus norvegicus) (300–450 g) obtained from Charles River Canada, St. Constant, Quebec. Rats were housed individually on a 12-h light:dark cycle (lights on at 0700 hours) with food and water freely available.
Startle apparatus
All testing was carried out in a dark and soundproof chamber. Detailed descriptions of the sound delivery and calibration systems have also been published elsewhere (29). Briefly, broad-band noise bursts (40 Hz–20 kHz; 10 ms in
Anatomical results
Injection of ibotenic acid into the IC or overlying cortex resulted in neural loss, gliosis, and some cavitation in the affected area. Restricted cortical lesions were made in the seven rats, and no neural damage was found in any subcortical structure (Fig. 1 ).
The histologic reconstruction for each rat with IC lesions are shown in Fig. 2. No damage was found beyond the IC that received injection of ibotenic acid.
General post-surgical observations
Rats receiving unilateral injection of ibotenic acid into the IC had brief and
Discussion
The results of the present study indicate that the IC makes an important contribution to acoustic PPI. The startle suppression that is normally augmented with an increase in prepulse sound level is reduced by unilateral restricted lesions of the IC. In contrast, damage to the cortex overlying IC has no effect on PPI. The present data are consistent with previous observations of the effects of radio-frequency lesions of the IC and surrounding areas (27) and, therefore, support the view that the
Acknowledgements
The authors gratefully acknowledge the assistance of Sharon David and Stephen Ferguson. This work was supported by a postdoctoral fellowship to L. L. and research grants to B. J. F. and R. J. B. from the Natural Sciences and Engineering Research Council of Canada.
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