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PhD Exit Seminar – Jennifer Lapierre (Peever lab)
October 7, 2015 @ 10:10 am - 11:10 am
PhD Exit Seminar
Wednesday October 7th, 10:10 am – Ramsay Wright Building, Rm. 432
Jennifer Lapierre (Peever lab)
“ Neurochemical Substrates of Unihemispheric Sleep in the Fur Seal”
Abstract
Several neuronal systems contribute to the generation and maintenance of sleep and waking. Knowledge pertaining to the neurotransmitters involved in sleep-wake regulation has been derived primarily from species that display bilaterally symmetric EEG states (e.g. cats, dogs, rats, and mice). Such studies, however, do not indicate which aspects of sleep these neurotransmitters are specifically linked to. Fur seals display both bilateral (BSWS) and asymmetrical sleep slow-wave sleep (ASWS); this unusual sleeping pattern provides a unique opportunity to determine which of the many physiological and neurochemical changes seen bilaterally in terrestrial mammals are linked to the cortical EEG changes and which may be linked to the motor and/or autonomic aspects of sleep. In studying this remarkable feature of the fur seal, we can dissociate the thalamocortical EEG activity in each hemisphere from aspects of behavioural state and study each independently as they relate to neurotransmitter release. The overall aim of my thesis was to examine, simultaneously in both hemispheres, the release of key neurotransmitters in the cortex across the sleep-wake cycle in the northern fur seal, and to specifically compare levels during BSWS and ASWS. In vivo microdialysis and high-performance liquid chromatography were used to monitor the release of neurotransmitters during polygraphically defined states. Neurotransmitters previously thought to contribute equally to the waking state, actually behave quite differently in a brain that is half awake and half asleep. Cortical acetylcholine (ACh) release was highly lateralized during ASWS, with greater release in the activated hemisphere, whereas cortical serotonin (5-HT), noradrenaline (NA), and histamine (HA) were symmetrically released during ASWS. Of the arousal systems studied so far, only ACh is involved in the lateralized cortical EEG activation manifested in asymmetric sleep. Bilaterally symmetric levels of the monoaminergic transmitters studied here are compatible with interhemispheric EEG asymmetry. Findings suggest distinct functional roles for ACh, 5-HT, NA, and HA in the regulation of wakefulness, with respect to cortical activation and behavioural arousal.
Ramsay Wright is a wheelchair accessible building.