Pedunculopontine Microinjection of Urotensin II Leads to an Increased Perception of Sensory Input
Ettaro, Robert J.
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The pedunculopontine tegmentum (PPTg) plays a role in the processing of multiple sensory inputs and innervates brain regions associated with reward related behaviors. Though there are three neuronal subtypes within the PPTg, here we focused on the cholinergic neurons. To selectively activate these cholinergic PPTg neurons, we utilized the Urotensin II receptor, activated by the Urotensin II peptide (UII). The exact function of cholinergic PPTg activation is unclear, it is thought to modify the perception of reward magnitude or salience detection. For drug reward models the incentive salience of drug-paired stimuli is thought to be critical for the maintenance of drug-seeking and relapse following a period of abstinence. Here we had three aims: first, determine if cholinergic activation is involved in natural reward (sucrose consumption), second, if so, distinguish the impact of the caloric value by utilizing saccharin, a zero calorie sweetener. Lastly, if the PPTg is multi-modal the perception of acoustic stimuli (acoustic startle reflex) should also be effected. Our results show that immediately following the microinjection of UII into the PPTg, consumption of both saccharin and sucrose is increased compared to controls. The significant difference in sucrose consumption lasted two days post treatment while saccharin consumption was significantly different for three days after treatment. The acoustic startle reflex was significantly increased the day after treatment for the UII treated group. Cholinergic activation by UII microinjection may lead to a miscalculation of the salience of external stimuli. This potential plastic change could therefore contribute to reward seeking behaviors.