EFFECTS OF THE NEUROTOXIN 3,3'-IMINODIPROPIONITRILE ON ACOUSTIC STARTLE AND LOCOMOTOR-ACTIVITY IN RATS - A COMPARISON OF FUNCTIONAL OBSERVATIONAL AND AUTOMATED STARTLE ASSESSMENT METHODS

Iminodipropionitrile (IDPN) is a neurotoxin that has been used in the validation of the U.S. Environmental Protection Agency's Functional Ob servational Battery (FOB), including acoustic startle. We compared the FOB clicker startle method to an automated procedure. IDPN was admini stered IP to male Long-Evans rats in three daily doses of 0, 100, 200, or 400 mg/kg (N = 8 per group). There was a significant effect of IDP N on clicker startle that was attributable to reduced startle in the I DPN-400 group. There were multiple significant effects of IDPN on auto mated startle. The overall effect of IDPN on automated startle was to reduce startle amplitude in the IDPN-400 and -200 groups. In addition, the IDPN-400 group showed startle reductions on all days, whereas the IDPN-200 group showed reduced startle primarily on day 1. IDPN also s ignificantly altered locomotor activity, which was included as an inte rnal check on IDPN's efficacy. The typical pattern of hypolocomotion w as found on day 2 posttreatment in the IDPN-400 and -200 groups, follo wed by hyperlocomotion on all subsequent days in the IDPN-400 group. T he startle results demonstrated that automated startle is more sensiti ve (at least for IDPN treatment), eliminates observer judgments, and p rovides interval-scaled data compared to the clicker method. However, automated startle also requires additional initial cost and more testi ng time per animal when multiple trials are presented. (C) 1998 Elsevi er Science Inc.