Adrenoceptor blockade modifies regional cerebral blood flow responses to hyperbaric hyperoxia: Protection against CNS oxygen toxicity.

Published online

Journal Article

Exposure to extreme-hyperbaric oxygen (HBO2), > 5-6 atmospheres absolute (ATA), produces baroreflex impairment, sympathetic hyperactivation, hypertension, tachycardia, and cerebral hyperemia, known as Phase II, culminating in seizures. We hypothesized that attenuation of the effects of high sympathetic outflow would preserve regional cerebral blood flow (rCBF) and protect against HBO2-induced seizures. To explore this possibility, we tested four adrenoceptor antagonists in conscious and anesthetized rats exposed to HBO2 at 5 and 6 ATA, respectively: phentolamine (nonselective α1 and 2), prazosin (selective α1), propranolol (nonselective β1 and 2) and atenolol (selective β1). In conscious rats, 4 drug-doses were administered to rats prior to HBO2 exposures, and seizure latencies were recorded. Drug-doses that provided similar protection against seizures were administered before HBO2 exposures in anesthetized rats to determine the effects of adrenoceptor blockade on mean arterial pressure, heart rate, rCBF and EEG spikes. All four drugs modified cardiovascular and rCBF responses in HBO2 that aligned with epileptiform discharges, but only phentolamine and propranolol effectively increased EEG spike latencies by ~20 and 36 min, respectively. When phentolamine and propranolol were delivered during HBO2 at the onset of phase II, only propranolol led to sustained reductions in heart rate and rCBF, preventing the appearance of epileptiform discharges. The enhanced effectiveness of propranolol may extend beyond β-adrenoceptor blockade, i.e. membrane stability and reduced metabolic activity. These results indicate that adrenoceptor drug pre-treatment will minimize the effects of excessive sympathetic outflow on rCBF and extend HBO2 exposure time.

Full Text

Duke Authors

Cited Authors

  • Gasier, HG; Demchenko, IT; Zhilyaev, SY; Moskvin, AN; Krivchenko, AI; Piantadosi, CA

Published Date

  • July 19, 2018

Published In

PubMed ID

  • 30024340

Pubmed Central ID

  • 30024340

Electronic International Standard Serial Number (EISSN)

  • 1522-1601

Digital Object Identifier (DOI)

  • 10.1152/japplphysiol.00540.2018

Language

  • eng

Conference Location

  • United States