Acetylcholine released from cholinergic nerves is involved in heat loss responses of cutaneous vasodilation and sweating. K(+) channels are thought to play a role in regulating cholinergic cutaneous vasodilation and sweating, though which K(+) channels are involved in their regulation remains unclear. We evaluated the hypotheses that 1) Ca(2+)-activated K(+) (KCa), ATP-sensitive K(+) (KATP), and voltage-gated K(+) (KV) channels all contribute to cholinergic cutaneous vasodilation; and 2) KV channels, but not KCa and KATP channels, contribute to cholinergic sweating. In 13 young adults (24 ± 5 years), cutaneous vascular conductance (CVC) and sweat rate were evaluated at intradermal microdialysis sites that were continuously perfused with: 1) lactated Ringer (Control), 2) 50 mM tetraethylammonium (KCa channel blocker), 3) 5 mM glybenclamide (KATP channel blocker), and 4) 10 mM 4-aminopyridine (KV channel blocker). At all sites, cholinergic cutaneous vasodilation and sweating were induced by coadministration of methacholine (0.0125, 0.25, 5, 100, and 2,000 mM, each for 25 min). The methacholine-induced increase in CVC was lower with the KCa channel blocker relative to Control at 0.0125 (1 ± 1 vs. 9 ± 6%max) and 5 (2 ± 5 vs. 17 ± 14%max) mM methacholine, whereas it was lower in the presence of KATP (69 ± 7%max) and KV (57 ± 14%max) channel blocker compared with Control (79 ± 6%max) at 100 mM methacholine. Furthermore, methacholine-induced sweating was lower at the KV channel blocker site (0.42 ± 0.17 mg·min(-1)·cm(-2)) compared with Control (0.58 ± 0.15 mg·min(-1)·cm(-2)) at 2,000 mM methacholine. In conclusion, we show that KCa, KATP, and KV channels play a role in cholinergic cutaneous vasodilation, whereas only KV channels contribute to cholinergic sweating in normothermic resting humans.

Edited by: Philip Atherton New Findings r What is the central question of this study?Acetylcholine released from cholinergic nerves can activate both muscarinic and nicotinic receptors. Although each receptor can independently induce cutaneous vasodilatation and eccrine sweating, it remains to be elucidated whether the two receptors interact in order to mediate these responses. r What is the main finding and its importance?We show that although nicotinic receptor activation does not modulate muscarinic cutaneous vasodilatation, it lowers the muscarinic receptor agonist threshold at which onset for eccrine sweating (augmentation of muscarinic eccrine sweating) occurs in young men in normothermic resting conditions. These results provide new insights into the physiological significance of nicotinic receptors in the regulation of cutaneous perfusion and eccrine sweating.Acetylcholine released from cholinergic nerves can activate both muscarinic and nicotinic receptors; each is known independently to induce cutaneous vasodilatation and eccrine sweating in humans. However, it is not known whether the two receptors interact in order to mediate cutaneous vasodilatation and eccrine sweating. In 10 young men (27 ± 6 years old), cutaneous vascular conductance and sweat rate were evaluated at intradermal microdialysis sites that were continuously perfused with either lactated Ringer's solution (control) or three different concentrations of nicotine (0.1, 1 and 10 mm), a nicotinic receptor agonist. Co-administration of methacholine, a muscarinic receptor agonist, was performed at all skin sites in a dose-proportional fashion (0.0125, 0.25, 5, 100 and 2000 mm, each for 25 min). Administration of nicotine alone caused dose-dependent transient increases in cutaneous vascular conductance and sweat rate (all P ࣘ 0.05), which thereafter returned to pre-nicotine levels, except that a portion of transient responses remained with continuous administration of 10 mm nicotine (both P ࣘ 0.05). Cutaneous vascular conductance was increased by administration of ࣙ0.25 mm methacholine at the control site, and this response was likewise observed in the presence of co-administration of all doses of nicotine used (all P ࣘ 0.05). Sweat rate at the control site was increased by administration of ࣙ0.25 mm methacholine, but the lowest dose of methacholine (0.0125 mm) was able to increase sweat rate in the presence of 10 mm nicotine (P ࣘ 0.05). We conclude that nicotinic receptor activation lowers the muscarinic

Background and Objectives:Seizures are common during neonatal encephalopathy, but the contribution of seizure burden to outcomes remains controversial. This study aims to examine the relationship between electrographic seizure burden and neurological outcomes after neonatal encephalopathy.Methods:This prospective cohort study recruited newborns ≥36 weeks PMA around 6 hours of life between August 2014 to November 2019 from a Neonatal Intensive Care Unit. Participants underwent continuous electroencephalography for at least 48 hours, brain MRI within 3-5 days of life, and structured follow-up at 18 months. Electrographic seizures were identified by board-certified neurophysiologists, and quantified as total seizure burden and maximum hourly seizure burden. A medication exposure score was calculated based on all anti-seizure medications given during NICU admission. Brain MRI injury severity was classified based on basal ganglia and watershed scores. Developmental outcomes were measured using the Bayley Scales of Infant Development, 3rdEdition. Multivariable regression analyses were performed, adjusting for significant potential confounders.Results:Of 108 enrolled subjects, 98 subjects had cEEG and MRI data collected, of which 5 were lost to follow-up, and 6 died before age 18 months. All subjects with moderate-severe encephalopathy completed therapeutic hypothermia. cEEG-confirmed neonatal seizures occurred in 21(24%) newborns, with a total seizure burden mean of 12.5 ± 36.4 minutes, and a maximum hourly seizure burden mean of 4 ± 10 min/hr. After adjusting for MRI brain injury severity and medication exposure, total seizure burden was significantly associated with lower cognitive (-0.21, 95%CI -0.33 – -0.08, p=0.002) and language (-0.25, 95%CI -0.39 – -0.11, p=0.001) scores at 18 months. Total seizure burden of 60 minutes was associated with 15-point decline in language scores, and 70 minutes for cognitive scores. However, seizure burden was not significantly associated with epilepsy, neuromotor score, or cerebral palsy (p>0.1).Discussion:Higher seizure burden during neonatal encephalopathy was independently associated with worse cognitive and language scores at 18 months, even after adjusting for exposure to anti-seizure medications and severity of brain injury. These observations support the hypothesis that neonatal seizures occurring during neonatal encephalopathy independently contribute to long-term outcomes.