Strychnine increases acoustic startle amplitude but does not alter short-term or long-term habituation.

Used the glycine antagonist strychnine (1.0 mg/kg, ip, 10 min before treatment) to investigate the involvement of glycinergic neurons in the development and/or expression of short-term (within-session) habituation (Exp I) and long-term (between-sessions) habituation (Exps II and III) of the acoustic startle response in 120 male albino Sprague-Dawley rats. Over a range of eliciting-stimulus intensities (95, 105, and 115 db) and interstimulus intervals (3, 7, 13, and 27 sec), strychnine markedly increased startle amplitude, relative to water injection, whereas it failed to attenuate the rate of within-session habituation (Exp I). In Exp II, Ss that were exposed to daily sessions of startle-eliciting stimuli for 4 days and then tested on Day 5 showed lower levels of startle amplitude than Ss with no prior habituation training. Strychnine injected prior to the test session again increased startle amplitude but did not block the expression of between-sessions habituation. In Exp III, Ss injected with either strychnine or water prior to each of 3 daily habituation training sessions and subsequently tested on Day 4 showed similar between-sessions habituation. In general, results show that strychnine increased startle amplitude without affecting either within-session or between-sessions habituation of acoustic startle. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)