Non-Photic Phase Shifting: Acetylcholine and Arousal
Date
2014-04-30
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Abstract
Non-photic stimuli are capable of producing large phase advances of the suprachiasmatic nuclei (SCN) during the midday in a manner that is different than light. Two prominent non-photic stimuli include confinement to a novel running wheel, and sleep deprivation by gentle handling. It was hypothesized that these stimuli both provide a sustained level of behavioral arousal to the animals in order to bring about phase shifts. If this was the case, then neurotransmitters involved in behavioral arousal should also participate in non-photic phase shifting. Neurotransmission of acetylcholine (ACh) is involved in bringing about arousal and also has been shown to play a role in the circadian system. The purpose of these experiments was to determine if ACh plays a role in non-photic phase shifting and to what extent arousal is involved. First, it was shown that Fos expression is increased in general areas containing ACh, orexin and histamine in Syrian hamsters undergoing sleep deprivation. Next, it was found that Fos expression specifically in cholinergic cells of the forebrain is increased in animals undergoing novel wheel confinement, but not sleep deprivation. It was then found that in vivo electrical stimulation of the basal forebrain region containing cholinergic neurons phase advanced circadian rhythms of wheel running activity at midday. The phase shifts to these stimulations was found to be dependent on a direct cholinergic input into the SCN. Finally, it was shown that blocking cholinergic neurotransmission in the SCN attenuates phase advances to novel wheel confinement. Taken together, these results show that ACh participates in non-photic phase shifting of the SCN through direct projections from forebrain cells. This also provides evidence for a role of behavioral arousal in novel wheel confinement induced phase shifts and a system that can feedback information on behavioral state onto the SCN.
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Neuroscience, Psychology--Behavioral, Psychology--Experimental
Citation
Yamakawa, G. (2014). Non-Photic Phase Shifting: Acetylcholine and Arousal (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27124