Microinjection of Urotensin Ii Into the Pedunculopontine Tegmentnum Leads to an Increased Perception of Sensory Stimuli

Abstract

The pedunculopontine tegmentum (PPTg) plays a role in processing multiple sensory inputs and innervates brain regions associated with reward‐related behaviors. The urotensin II receptor, activated by the urotensin II peptide (UII), is selectively expressed by the cholinergic neurons of the PPTg. Although the exact function of cholinergic neurons of the PPTg are unknown, they are thought to modify the perception of reward magnitude or salience detection. We hypothesized that the activation of PPTg cholinergic neurons would alter sensory processing across multiple modalities (ex. taste and hearing). Here we had three aims: first, determine if cholinergic activation is involved in consumption behavior. Second, if so, distinguish the impact of the caloric value by using saccharin, a zero calorie sweetener. Lastly, we tested the perception of acoustic stimuli by measuring the acoustic startle reflex (ASR).Male Sprague‐Dawley rats were bilaterally cannulated into the PPTg, then housed in a contact lickometer and placed under food restriction lasting the entire consumption experiment (water ad lib.). The lickometer recorded each individual lick to give insight into the microstructure of the consumption behavior. Treatment consisted of a microinjection of either 1 μL of aCSF or 1 μL of 10 μM UII into the PPTg, and the rats were immediately given access to either sucrose or saccharin. For the remaining five days rats were allowed one hour access per day to the same sweet solution without any further treatments. ASR testing consisted of a baseline (no treatment), treatment day, and two additional days (no treatment). Immediately following the microinjection of UII, consumption of both saccharin and sucrose 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 ASR was significantly increased the day after treatment in the rats treated with UII.Activating cholinergic PPTg neurons may lead to a miscalculation of the salience of external stimuli, implicating the importance of cholinergic input in modulating a variety of behaviors. This potential plastic change can give rise to further studies in the role of sensory processing on reward related‐behaviors at the level of the PPTg cholinergic neurons.Support or Funding InformationThe Howard T. Blane Director's Award in the Addictions (BDAA) from Research Institute on AddictionThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.