Cortico-pontine theta carrier frequency phase shif across sleep/wake states following monoaminergic lesion in rat

Abstract

This study was aimed to explore the sleep/wake states related cortico-pontine theta carrier frequency phase shif following a systemically induced chemical axotomy of the monoaminergic afferents within a brain of the freely moving rats. Our experiments were performed in 14 adult, male Sprague Dawley rats, chronically implanted for sleep recording. We recorded sleep during baseline condition, following sham injection (saline i.p. 1 ml/kg), and every week for 5 weeks following injection of the systemic neurotoxins (DSP-4 or PCA; 1 ml/kg, i.p.) for chemical axotomy of the locus coeruleus (LC) and dorsal raphe (DR) axon terminals. Afer sleep/wake states identification, FFT analysis was performed on 5 s epochs. Theta carrier frequency phase shif (ΔΠ) was calculated for each epoch by averaging theta Fourier component phase shifs, and the ΔΠ values were plotted for each rat in control condition and 28 days following the monoaminergic lesions, as a time for permanently established DR or LC chemical axotomy. Calculated group averages have shown that ΔΠ increased between pons and cortex significantly in all sleep/wake states (Wake, NREM and REM) following the monoaminergic lesions, with respect to controls. Monoaminergic lesions established the pontine leading role in the brain theta oscillations during all sleep/wake states.