Orthostatic hypotension and subjective symptomatic orthostasis in Parkinson's disease: Associations and correlations.

Background: Both measured orthostatic hypotension and symptomatic orthostasis are common in PD but their relationship is unclear. Objective: We aim to determine clinical predictors of both measured orthostatic hypotension and reported symptomatic orthostasis in PD, including the impact of "on"/"off" status and seasons, and to determine the correlation between measured OH and subjective orthostasis. Methods: We analyzed BP readings, demographic and disease state predictors for both 1. Measured blood pressure OH criteria and 2. The subjective report of orthostatic symptoms, using logistic regression analyses from an initial "on" motor state clinical visit in all PD patient visits. We then correlated subjective orthostasis symptoms with BP measurements. We also compared intra-subject BP measures in PD patients seen in both "on" and "off" states, and when seen "on" in both summer and winter. Results: 723 consecutive visits over 2 years identified 250 unique PD individuals. Subjective orthostasis was reported by 44 % and "on" measured OH (>20 drop in SBP or 10 DBP upon standing) was seen in 30 %. Measured OH did not significantly correlate with any assessed clinical feature or specific medicine. Subjective orthostasis correlated most with older age, dementia, and L-dopa use. Subjective orthostasis correlated equally with absolute lower measured standing SBP and the drop in SBP from sitting to standing. Compared to the "off" state, "on" state showed lower sitting and standing SBP, more than DBP, but no significant change in BP drop upon standing. Seasons did not impact measured BP. Conclusions: Both OH and symptomatic orthostasis are common. Dopaminergic medications did not cause traditionally defined OH but lowered all SBP (sitting and standing) and thus reduced pulse pressure, possibly by increasing arteriole compliance simply by reducing motor tone, as this BP-lowering effect may be specific to Parkinsonism.

Indoleamine 2,3-dioxygenase-dependent neurotoxic kynurenine metabolism mediates inflammation-induced deficit in recognition memory.

Cognitive dysfunction in depression is a prevalent and debilitating symptom that is poorly treated by the currently available pharmacotherapies. Research over the past decade has provided evidence for proinflammatory involvement in the neurobiology of depressive disorders and symptoms associated with these disorders, including aspects of memory dysfunction. Recent clinical studies implicate inflammation-related changes in kynurenine metabolism as a potential pathogenic factor in the development of a range of depressive symptoms, including deficits in cognition and memory. Additionally, preclinical work has demonstrated a number of mood-related depressive-like behaviors to be dependent on indoleamine 2,3-dioxygenase-1 (IDO1), the inflammation-induced rate-limiting enzyme of the kynurenine pathway. Here, we demonstrate in a mouse model, that peripheral administration of endotoxin induced a deficit in recognition memory. Mice deficient in IDO were protected from cognitive impairment. Furthermore, endotoxin-induced inflammation increased kynurenine metabolism within the perirhinal/entorhinal cortices, brain regions which have been implicated in recognition memory. A single peripheral injection of kynurenine, the metabolic product of IDO1, was sufficient to induce a deficit in recognition memory in both control and IDO null mice. Finally, kynurenine monooxygenase (KMO) deficient mice were also protected from inflammation-induced deficits on novel object recognition. These data implicate IDO-dependent neurotoxic kynurenine metabolism as a pathogenic factor for cognitive dysfunction in inflammation-induced depressive disorders and a potential novel target for the treatment of these disorders.

The attentional set shifting task: a measure of cognitive flexibility in mice.

Cognitive impairment, particularly involving dysfunction of circuitry within the prefrontal cortex (PFC), represents a core feature of many neuropsychiatric and neurodevelopmental disorders, including depression, post-traumatic stress disorder, schizophrenia and autism spectrum disorder. Deficits in cognitive function also represent the most difficult symptom domain to successfully treat, as serotonin reuptake inhibitors and tricyclic antidepressants have only modest effects. Functional neuroimaging studies and postmortem analysis of human brain tissue implicate the PFC as being a primary region of dysregulation in patients with these disorders. However, preclinical behavioral assays used to assess these deficits in mouse models which can be readily manipulated genetically and could provide the basis for studies of new treatment avenues have been underutilized. Here we describe the adaptation of a behavioral assay, the attentional set shifting task (AST), to be performed in mice to assess prefrontal cortex mediated cognitive deficits. The neural circuits underlying behavior during the AST are highly conserved across humans, nonhuman primates and rodents, providing excellent face, construct and predictive validity.

Polymorphism in endothelial connexin40 enhances sensitivity to intraluminal pressure and increases arterial stiffness.

OBJECTIVE: To determine whether impairment of endothelial connexin40 (Cx40), an effect that can occur in hypertension and aging, contributes to the arterial dysfunction and stiffening in these conditions. APPROACH AND RESULTS: A new transgenic mouse strain, expressing a mutant Cx40, (Cx40T202S), specifically in the vascular endothelium, has been developed and characterized. This mutation produces nonfunctional hemichannels, whereas gap junctions containing the mutant are electrically, but not chemically, patent. Mesenteric resistance arteries from Cx40T202S mice showed increased sensitivity of the myogenic response to intraluminal pressure in vitro, compared with wild-type mice, whereas transgenic mice overexpressing native Cx40 (Cx40Tg) showed reduced sensitivity. In control and Cx40Tg mice, the sensitivity to pressure of myogenic constriction was modulated by both NO and endothelium-derived hyperpolarization; however, the endothelium-derived hyperpolarization component was absent in Cx40T202S arteries. Analysis of passive mechanical properties revealed that arterial stiffness was enhanced in vessels from Cx40T202S mice, but not in wild-type or Cx40Tg mice. CONCLUSIONS: Introduction of a mutant form of Cx40 in the endogenous endothelial Cx40 population prevents endothelium-derived hyperpolarization activation during myogenic constriction, enhancing sensitivity to intraluminal pressure and increasing arterial stiffness. We conclude that genetic polymorphisms in endothelial Cx40 can contribute to the pathogenesis of arterial disease.