Electronic Thesis and Dissertation Repository


Master of Science


Anatomy and Cell Biology


Dr. Susanne Schmid

2nd Supervisor

Dr. Raj Rajakumar

Joint Supervisor


The acoustic startle response (ASR) is mediated by a simple pathway which includes the giant neurons of the caudal pontine reticular nucleus (PnC). Habituation is theorized to occur via hyperpolarizing big potassium (BK) channels localized at glutamatergic terminals of auditory afferents in the PnC. Prepulse inhibition is suggested to be mediated by cholinergic innervation of PnC giant neurons, with possible glutamate and/or GABA co-release. Animals were injected with Fluorogold at C3/C4 to label a subpopulation of PnC giant neurons, and following a startle experiment, brainstems were processed for pCREB expression. Using their respective markers, BK channels, glutamatergic, GABAergic, and cholinergic terminals were also stained. pCREB expression overlapped with retrogradely-labeled PnC giant neurons of startled animals but not controls, supporting their startle-mediating role. Dual-staining shows some BK channel expression on glutamatergic terminals and glutamate/GABA co-expression in a subpopulation of cholinergic terminals which validate their respective implications in habituation or prepulse inhibition of startle.