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Chemosensitive signaling of locus coeruleus neurons in the Bullfrog, Lithobates catesbeianus
Author(s) -
Santin Joseph,
Hartzler Lynn
Publication year - 2012
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.26.1_supplement.886.20
Subject(s) - bullfrog , lithobates , excitatory postsynaptic potential , locus coeruleus , electrophysiology , brainstem , neuroscience , inhibitory postsynaptic potential , biology , membrane potential , medicine , endocrinology , chemistry , central nervous system
Bullfrogs, Lithobates catesbeianus , experience broad changes in pH inversely proportional to temperature while retaining whole body CO 2 stores. Ventilatory patterns to maintain constant CO 2 are controlled through negative feedback with chemosensory neurons detecting CO 2 /pH. We hypothesize that neurons of the locus coeruleus (LC) will respond to hypercapnic acidosis (HA). Whole‐cell patch‐clamp electrophysiological techniques were used to measure firing rates in excitatory (chemosensitivity index (CI)=260±35%), inhibitory (CI=24±18%), and non‐chemosensitive (CI=105±3%) LC neurons in bullfrog brainstem slice preparations. LC neurons have resting membrane potentials of −42±0.6mV, and when stimulated by HA membrane potentials are depolarized to −39±0.7mV ( p <0.001). 81% of neurons increased and 11% decreased firing rates when exposed to HA, though increasing ΔCO 2 to acidify the superfusate by >2‐fold (0.13–0.33pH units) did not produce different firing rates ( p > 0.5). Greater than 80% of LC neurons are excited by HA which corroborate percentages typically reported for neonatal rat LC neurons; however, bullfrog excitatory output is doubled and appears to be maximally activated with lower CO 2 /H + changes compared with neonatal rats. Our data begin to provide insight into a neurological mechanism for α‐stat pH regulation in bullfrogs based on chemosensitivity to CO 2 /pH.