Spike firing allometry in avian intrapulmonary chemoreceptors: Matching neural code to body size

S. C. Hempleman, D. L. Kilgore, C. Colby, R. W. Bavis, F. L. Powell

Research output: Contribution to journalArticle

11 Scopus citations

Abstract

Biological rates in small animals are usually higher than those in large animals, yet the maximal rate of action potential (spike) generation in sensory neurons encoding rate functions is similar in all animals, due to the conserved genetics of voltage-gated ion channels. Therefore, sensory signals that vary at rates approaching maximal spike generation rate, as might occur in animals of diminished body size, may require specialized spike coding to convey this information. To test whether spike coding scales allometrically in sensory neurons monitoring signals that change frequency with body size, we recorded action potentials from 70 avian intrapulmonary chemoreceptors (IPC), respiratory neurons that detect lung CO2 changes during breathing, in five different avian species ranging in size from body mass Mb = 0.045 kg (lovebirds) to 5.23 kg (geese). Since breathing frequency scales approximately to Mb-1/4 (higher in small birds, lower in large birds), we reasoned that IPC discharge frequencies may also scale to maintain spike information transmission within each breath. We found that phasic action potential discharge pattern, as quantified by the peak discharge rate and the magnitude of spike frequency adaptation, scaled between Mb -0.22 and Mb-0.26, like breathing rate (P<0.05). Previously published values of peak discharge rate in IPC also fit this allometric relationship. We suggest that mass-dependent scaling of neural coding may be necessary for preserving information transmission with decreasing body size.

Original languageEnglish (US)
Pages (from-to)3065-3073
Number of pages9
JournalJournal of Experimental Biology
Volume208
Issue number16
DOIs
StatePublished - Aug 1 2005

Keywords

  • Allometry
  • Bird
  • Body size
  • Intrapulmonary chemoreceptors
  • Neural coding

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Aquatic Science
  • Animal Science and Zoology
  • Molecular Biology
  • Insect Science

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