Voxel-based morphometry (VBM) is a powerful analytical tool based on structural MRI data [14] that has been widely used to evaluate brain morphological alternations in different chronic pain syndromes [15, 16].
These results are consistent with the threshold-liability model of BD, and demonstrate the usefulness of the PGR-BD score in identifying brain functional alternations associated with vulnerability to BD.
One of the fundamental mysteries of sleep is the production of brain state alternations, i.e., the REM/nREM cycle.
Thus, stimulation of forebrain-activating brainstem sites implicated in the pacing of cyclical brain state alternations during sleep subsequently disrupts state cycling under urethane anaesthesia.
Brain state alternations under urethane were also correlated to other physiological fluctuations that showed further similarities to REM/nREM cycles during natural sleep.
Thus, alternations in brain state exhibited under urethane anaesthesia were correlated with physiological changes consistent with those exhibited during natural sleep.
Based upon these data, we consider that urethane anaesthesia constitutes a viable and realistic model system for the alternations of brain state present during natural sleep.
The use of urethane anaesthesia as a model system will facilitate mechanistic studies into sleep-like brain states and their alternations.
Despite successful pre-treatments with reserpine, all subsequently anaesthetized animals displayed spontaneous and rhythmic alternations of brain state demonstrating both activated and deactivated patterns (Figure 9).
The brain mechanisms of state alternations under urethane also closely overlapped those of natural sleep in their sensitivity to cholinergic pharmacological agents and dependence upon activity in the basal forebrain nuclei that are the major source of forebrain acetylcholine.
