GAL-021 and GAL-160 are Efficacious in Rat Models of Obstructive and Central Sleep Apnea and Inhibit BKCa in Isolated Rat Carotid Body Glomus Cells

Abstract

Abstract. GAL-021 and GAL-160 are alkylamino triazine analogues, which stimulate ventilation in rodents, non-human primates and (for GAL-021) in humans. To probe the site and mechanism of action of GAL-021 and GAL-160 we utilized spirometry in urethane anesthetized rats subjected to acute bilateral carotid sinus nerve transection (CSNTX) or sham surgery. In addition, using patch clamp electrophysiology we evaluated ionic currents in carotid body glomus cells isolated from neonatal rats. Acute CSNTX markedly attenuated and in some instances abolished the ventilatory stimulant effects of GAL-021 and GAL-160 (0.3 mg/kg IV), suggesting the carotid body is a/the major locus of action. Electrophysiology studies, in isolated Type I cells, established that GAL-021 (30 µM) and GAL-160 ( 30 µM) inhibited the BKCa current without affecting the delayed rectifier K + , leak K + or inward Ca 2+ currents. At a higher concentration of GAL-160 (100 µM), inhibition of the delayed rectifier K + current and leak K + current were observed. These data are consistent with the concept that GAL-021 and GAL-160 influence breathing control by acting as peripheral chemoreceptor modulators predominantly by inhibiting BKCa mediated currents in glomus cells of the carotid body.

Systemic Administration of Tempol Attenuates the Cardiorespiratory Depressant Effects of Fentanyl

“…The effects of bolus intravenous (IV) injections of vehicle (saline), Tempol (25, 50 or 100 mg/kg; stock solutions of Tempol of 100 mg/ml in 0.9% saline were prepared freshly) and fentanyl (5 μg/kg) on heart rate (HR) and mean (MAP), diastolic (DBP) and systolic (SBP) blood pressures, and frequency of breathing (Freq), tidal volume (TV) and minute ventilation (MV) were evaluated in anesthetized spontaneously breathing rats by methods described previously ( Dallas et al, 2015 ; Golder et al, 2015 ). In brief, rats were anesthetized with 2–2.5% isoflurane in compressed air.…”

“…Ventilatory parameters were continuously recorded in unrestrained freely moving rats via a whole-body 12-chamber plethysmography system (PLY 3223; BUXCO Inc., Wilmington, NC, United States) as described previously ( Henderson et al, 2013 ; May et al, 2013a ; May et al, 2013b ; Henderson et al, 2014 ; Dallas et al, 2015 ; Baby et al, 2018 ). In brief, each rat was placed in an individual plexiglass chamber and the venous line was attached to a swivel assembly on the roof of the chamber to allow drug injections.…”

“…The respiratory flow waveform was derived from a pneumotachometer in the chamber wall. Respiratory flow, chamber temperature, and humidity were measured continuously and used to calculate TV using the Epstein and Epstein algorithm ( Henderson et al, 2013 ; May et al, 2013a ; May et al, 2013b ; Henderson et al, 2014 ; Dallas et al, 2015 ; Baby et al, 2018 ). The respiratory flow waveform cycle period was used to calculate Freq.…”

High Efficacy by GAL-021: A Known Intravenous Peripheral Chemoreceptor Modulator that Suppresses BKCa-Channel Activity and Inhibits IK(M) or Ih

“…GAL-021 has recently been developed as a novel breathing control modulator thought to preserve respiratory drive and to protect patients from the respiratory impairment resulting from opioids and other modalities; moreover, it notably did not influence analgesia [1][2][3][4][5][6][7]. The studies have also reported that this agent is an experimental drug demonstrated to inhibit Ca 2+ -activated K + channels with big conductance functionally expressed on type 1 cells of the carotid bodies [1,8,9]. However, to what extent this compound perturbs other patterns of voltage-gated ionic currents has not yet been determined.…”

Effective Activation of BKCa Channels by QO-40 (5-(Chloromethyl)-3-(Naphthalen-1-yl)-2-(Trifluoromethyl)Pyrazolo [1,5-a]pyrimidin-7(4H)-one), Known to Be an Opener of KCNQ2/Q3 Channels

“…We next tested whether the stimulatory effect of QO-40 on I K(Ca) was attenuated by linopirdine, TRAM-34, GAL-021, or paxilline. Linopirdine inhibits M-type K + current ( I K(M) ), and TRAM-34 inhibits intermediate-conductance Ca 2+ -activated K + (IK Ca ) channels [ 15 , 22 , 23 ], while GAL-021 and paxilline suppress the activity of large-conductance Ca 2+ -activated K + (BK Ca ) channels [ 21 , 24 , 25 ]. As demonstrated in Figure 3 , when cells were continually exposed to QO-40 (3 μM), neither linopirdine (10 μM) nor TRAM-34 (3 μM) could attenuate QO-40-stimulated I K(Ca) ; conversely, the subsequent addition of GAL-021 (3 μM) or paxilline (1 μM) led to effective attenuation of the increase in I K(Ca) amplitude.…”