ODOR IDENTIFICATION ABILITY PREDICTS CHANGES IN SYMPTOMS OF PSYCHOPATHOLOGY FOLLOWING 56 H OF SLEEP DEPRIVATION

Olfactory impairment in the rotenone model of Parkinson's disease is associated with bulbar dopaminergic D2 activity after REM sleep deprivation

Olfactory and rapid eye movement (REM) sleep deficits are commonly found in untreated subjects with a recent diagnosis of Parkinson's disease (PD). Additionally, different studies report declines in olfactory performance during a short period of sleep deprivation. Mechanisms underlying these clinical manifestations are poorly understood, and impairment of dopamine (DA) neurotransmission in the olfactory bulb and the nigrostriatal pathway may have important roles in olfaction and REM sleep disturbances. Therefore, we hypothesized that modulation of the dopaminergic D2 receptors in the olfactory bulb could provide a more comprehensive understanding of the olfactory deficits in PD and REM sleep deprivation (REMSD). We decided to investigate the olfactory, neurochemical, and histological alterations generated through the administration of piribedil (a selective D2 agonist) or raclopride (a selective D2 antagonist) within the glomerular layer of the olfactory bulb, in rats subjected to intranigral rotenone and REMSD. Our findings provide evidence of the occurrence of a negative correlation (r = -0.52, P = 0.04) between the number of periglomerular TH-ir neurons and the bulbar levels of DA in the rotenone, but not sham, groups. A significant positive correlation (r = 0.34, P = 0.03) was observed between nigrostriatal DA levels and olfactory discrimination index (DI) for the sham groups, indicating that increased DA levels in the substantia nigra pars compacta (SNpc) are associated with enhanced olfactory discrimination performance. Also, increased levels in bulbar and striatal DA were induced by piribedil in the rotenone control and rotenone REMSD groups, consistent with reductions in the DI. The present evidence reinforce the idea that DA produced by periglomerular neurons, particularly the bulbar dopaminergic D2 receptors, is an essential participant in olfactory discrimination processes, as the SNpc, and the striatum.

Odor identification ability predicts executive function deficits following sleep deprivation

Odor identification ability is sensitive to prefrontal lobe dysfunction and preliminary evidence suggests that this capacity may decline with prolonged wakefulness. We hypothesized that declines in odor identification during a single night of sleep loss might, therefore, be predictive of prefrontal lobe executive function deficits following an additional night of sleep deprivation. Change scores between two administrations of the University of Pennsylvania Smell Identification Test (SIT) during 24 hr of sleep deprivation were used to predict performance on the Wisconsin Card Sorting Test (WCST) following 45 hr of wakefulness in 54 healthy adults. Declines in SIT performance predicted poorer performance on the WCST following an additional night of sleep loss. These findings suggest that individual differences in vulnerability to the effects of sleep loss on odor identification ability are predictive of deficits in executive functioning following additional wakefulness. Odor identification ability may provide an unobtrusive method for assessing vulnerability to sleep deprivation.