Datensatz

Zusammenfassung

Alerting sensory stimuli activate the noradrenaline (NE) neurons of the Locus Coeruleus (LC) and the associated NE release improves sensory signaling. Impairments of the LC-NE system lead to sensory gating deficits that are widely studied using the Prepulse Inhibition paradigm (PPI) ? a reduction in acoustic startle response produced by a preceding non-alerting stimulus. In order to examine the specific role of LC-NE system in PPI we studied the behavioral startle response and the sensory evoked potential in the medial prefrontal cortex (mPFC) to an acoustic startle pulse (broad band noise, 20ms, 100dB) preceded by either an auditory prepulse (10kHz, 20ms, 70dB) or direct LC stimulation of different frequencies (20, 50 or 100Hz, 50µA, 100ms). Phasic activation of LC 100ms before startle stimulus resulted in PPI, which was proportional to stimulation intensity. The PPI to the highest stimulation frequency (60 startle response reduction) was comparable to standard auditory PPI (73).The LC stimulation 200ms before startle stimulus was not effective. The auditory prepulse stimulus but not the direct LC stimulation significantly decreased the amplitude of the mPFC evoked potential to startle stimulus. Thus, LC-NE system is critically involved in sensorimotor gating but auditory- and LC stimulation-induced PPI are likely mediated by different neural mechanisms.