Central respiratory chemoreception is the mechanism by which the CNS maintains physiologically appropriate pH and PCO₂via control of breathing. A prominent hypothesis holds that neural substrates for this process are distributed widely in the respiratory network, especially because many neurons that make up this network are chemosensitivein vitro. We and others have proposed that TASK channels (TASK-1, K_2P3.1 and/or TASK-3, K_2P9.1) may serve as molecular sensors for central chemoreception because they are highly expressed in multiple neuronal populations in the respiratory pathway and contribute to their pH sensitivityin vitro. To test this hypothesis, we examined the chemosensitivity of two prime candidate chemoreceptor neuronsin vitroand tested ventilatory responses to CO₂using TASK channel knock-out mice. The pH sensitivity of serotonergic raphe neurons was abolished in TASK channel knock-outs. In contrast, pH sensitivity of neurons in the mouse retrotrapezoid nucleus (RTN) was fully maintained in a TASK null background, and pharmacological evidence indicated that a K⁺channel with properties distinct from TASK channels contributes to the pH sensitivity of rat RTN neurons. Furthermore, the ventilatory response to CO₂was completely retained in single or double TASK knock-out mice. These data rule out a strict requirement for TASK channels or raphe neurons in central respiratory chemosensation. Furthermore, they indicate that a non-TASK K⁺current contributes to chemosensitivity of RTN neurons, which are profoundly pH-sensitive and capable of driving respiratory output in response to local pH changesin vivo.

Background: Current guidelines suggest treating blood pressure above 180/105 mm Hg during the first 24 hours in patients with acute ischemic stroke undergoing any form of recanalization therapy. Currently, no studies exist to guide blood pressure management in patients with stroke treated specifically with mechanical thrombectomy. We aimed to determine the association between blood pressure parameters within the first 24 hours after mechanical thrombectomy and patient outcomes. Methods and Results: We retrospectively studied a consecutive sample of adult patients who underwent mechanical thrombectomy for acute ischemic stroke of the anterior cerebral circulation at 3 institutions from March 2015 to October 2016. We collected the values of maximum, minimum, and average values of systolic blood pressure, diastolic blood pressure, and mean arterial pressures in the first 24 hours after mechanical thrombectomy. Primary and secondary outcomes were patients’ functional status at 90 days measured on the modified Rankin scale and the incidence and severity of intracranial hemorrhages within 48 hours. Associations were explored using an ordered multivariable logistic regression analyses. A total of 228 patients were included (mean age 65.8±14.3; 104 males, 45.6%). Maximum systolic blood pressure independently correlated with a worse 90‐day modified Rankin scale and hemorrhagic complications within 48 hours (adjusted odds ratio=1.02 [1.01–1.03], P =0.004; 1.02 [1.01–1.04], P =0.002; respectively) in multivariable analyses, after adjusting for several possible confounders. Conclusions: Higher peak values of systolic blood pressure independently correlated with worse 90‐day modified Rankin scale and a higher rate of hemorrhagic complications. Further prospective studies are warranted to identify whether systolic blood pressure is a therapeutic target to improve outcomes.

Propranolol is a widely used, non-selective β-adrenergic receptor antagonist with proven efficacy in treating cardiovascular disorders and in the prevention of migraine headaches. At plasma concentrations exceeding those required for β-adrenergic receptor inhibition, propranolol also exhibits anti-arrhythmic (“membrane stabilizing”) effects that are not fully explained by β-blockade. Previous in vitro studies suggested that propranolol may have local anesthetic effects. We directly tested the effects of propranolol on heterologously expressed recombinant human cardiac (NaV1.5) and brain (NaV1.1, NaV1.2, NaV1.3) sodium channels using whole-cell patch-clamp recording. We found that block was not stereospecific as we observed approximately equal IC50 values for tonic and use-dependent block by R-(+) and S-(−) propranolol (tonic block: R: 21.4 μM vs S: 23.6 μM; use-dependent block: R: 2.7 μM vs S: 2.6 μM). Metoprolol and nadolol did not block NaV1.5 indicating that sodium channel block is not a class effect of β-blockers. The biophysical effects of R-(+)-propranolol on NaV1.5 and NaV1.1 resembled that of the prototypical local anesthetic lidocaine including the requirement for a critical phenylalanine residue (F1760 in NaV1.5) in the domain 4 S6 segment. Finally, we observed that brain sodium channels exhibited less sensitivity to R-(+)-propranolol than NaV1.5 channels. Our findings establish sodium channels as targets for propranolol and may help explain some beneficial effects of the drug in treating cardiac arrhythmias, and may explain certain adverse central nervous system effects.