Comparison of two sensitization paradigms of the acoustic startle responsein Wistar and Sprague-Dawley rats

An increase in general responsiveness after aversive stimulation has provid ed a most widely accepted and well-understood sensitization paradigm. Accor ding to a second paradigm (based on the dual process theory of habituation and sensitization), not only additional aversive stimuli, but also the resp onse-eliciting stimuli themselves, induce sensitization. To relate these tw o sensitization paradigms, we compared the course of startle response param eters during repetitive acoustic stimulation with the change in startle amp litude after electric footshocks in outbred Wistar and Sprague-Dawley rats. Compared to the Wistar rats used, the Sprague-Dawley rats showed a lower r esponse decrement and a shortened latency during repetitive stimulation, bo th of which are indicators of increased sensitization by the startle-elicit ing stimuli. In addition, the Sprague-Dawley rats also demonstrated a reduc ed increase in startle amplitude following footshock. This was postulated t o be a consequence of the strong sensitization by startle-eliciting stimuli , which interferes with sensitization elicited by footshock. Because our Wi star and Sprague-Dawley rats did not differ in initial startle amplitude, b ut mainly in susceptibility to sensitization, further comparisons of these genetically different stocks of rats seem to be of potential value in study ing differences in fear-motivated behavior.