The expression of prepulse inhibition of the acoustic startle reflex as a function of three pulse stimulus intensities, three prepulse stimulus intensities, and three levels of startle responsiveness in C57BL6/J mice

Using the acoustic startle reflex, prepulse inhibition (PPI) is typically demonstrated by the interaction between two auditory stimuli presented in close temporal proximity. When a startle-eliciting pulse stimulus is shortly preceded by a weak prepulse stimulus, the reaction to the former is attenuated in comparison to when the pulse stimulus is presented alone. The present experiment evaluated the influence of different prepulse and pulse intensities upon the expression of PPI by additionally taking into account individual differences in startle reactivity. To this end, we subdivided a cohort of 102 mice into three subsets of equal size differing in startle responsiveness, and evaluated PPI using three levels of prepulse stimulus in combination with three intensities of pulse stimulus. Our results revealed additive as well as complex interactive effects amongst individual's reactivity, pulse intensity and prepulse intensity. At the same time, additional issues concerning the quantification of PPI are highlighted, especially when startle reactivity differs considerably between comparison groups. We concluded that the variation in pulse intensity represents a valuable addition to PPI assessment in general, and especially in genetically modified mice. (c) 2005 Published by Elsevier B.V.