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Reactive Oxygen Species Signaling in the Hypoxia‐Tolerant Turtle and Goldfish Stellate and Pyramidal Neurons Is Species Specific
Author(s) -
Buck Les,
HossienJavaheri Nariman,
Pillai Varshinie,
Hawrysh Peter
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1075.5
Subject(s) - reactive oxygen species , hypoxia (environmental) , turtle (robot) , biology , anatomy , microbiology and biotechnology , chemistry , oxygen , ecology , organic chemistry
The majority of vertebrate species are not hypoxia‐tolerant; however, some freshwater turtles and fish from the carp family are tolerant of extreme hypoxia for days or months. Two examples are the western painted turtle and the goldfish which provide excellent models for the study of hypoxia‐tolerance mechanisms in brain. We have previously shown that severe hypoxia results in a natural decrease in reactive oxygen species (ROS) in turtle brain; therefore, here we investigate in a turtle brain sheet and goldfish brain slice model the response of pyramidal and stellate neurons to scavenging of ROS with MPG (N‐2‐mercaptopropionyl glycine) for comparison to the tissue exposed to severe hypoxia. Using single cell fluorescence we first confirm that ROS levels do indeed decrease with severe hypoxia in goldfish brain slices. Then using whole‐cell and perforated patch clamp techniques and ROS scavenging we find that whole cell conductance (G w ) increases from 4.5 to 6.6nS in both turtle cell types and from 3.96±0.95nS to 6.84±0.62nS in both goldfish cell types. In both cases the increased G w is related to increased GABA‐A receptor conductance since application of the GABA‐A receptor inhibitor gabazine blocks the increase. While goldfish and turtle pyramidal cells remained mostly quiescent the action potential frequency (AP f ) of goldfish stellate neurons increased with ROS scavenging from 0.03±0.009Hz to 2.04±0.12Hz or 68 fold. Turtle stellate neurons exhibited a unique burst firing pattern where AP's are clustered into discrete bursts of about 2 AP's per burst with quiescent periods in between bursts. When exposed to ROS scavenging overall AP f decreased from 0.49 ± 0.14 Hz to 0.33 ± 0.07 Hz but the number of AP's per burst increased from 2.4 ± 0.21 to 3.0 ± 0.12. With ROS scavenging the stellate neuron burst pattern coalesces into a burst every 7–8 s that corresponds with the frequency of giant inhibitory GABAergic current recorded from pyramidal neurons. It remains unclear how these differences in ROS signaling impacts the hypoxia‐tolerance of each species but we conclude that the unique responses of stellate neurons is species specific. Support or Funding Information Natural Sciences and Engineering Council of Canada grant to LTB