National Institute of Science and Technology in Comparative Physiology INCT

Brazil

National Institute of Science and Technology in Comparative Physiology INCT

Brazil
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Patrone L.G.A.,São Paulo State University | Patrone L.G.A.,National Institute of Science and Technology in Comparative Physiology INCT | Bicego K.C.,São Paulo State University | Bicego K.C.,National Institute of Science and Technology in Comparative Physiology INCT | And 4 more authors.
Respiratory Physiology and Neurobiology | Year: 2014

The locus coeruleus (LC) plays an important role in central chemoreception. In young rats (P9 or younger), 85% of LC neurons increase firing rate in response to hypercapnia vs. only about 45% of neurons from rats P10 or older. Carbenoxolone (CARB - gap junction blocker) does not affect the % of LC neurons responding in young rats but it decreases the % responding by half in older animals. We evaluated the participation of gap junctions in the CO2 ventilatory response in unanesthetized adult rats by bilaterally microinjecting CARB (300μM, 1mM or 3mM/100nL), glycyrrhizic acid (GZA, CARB analog, 3mM) or vehicle (aCSF - artificial cerebrospinal fluid) into the LC of Wistar rats. Bilateral gap junction blockade in LC neurons did not affect resting ventilation; however, the increase in ventilation produced by hypercapnia (7% CO2) was reduced by ~25% after CARB 1mM or 3mM injection (1939.7±104.8mLkg-1min-1 for the aCSF group and 1468.3±122.2mLkg-1min-1 for 1mM CARB, P<0.05; 1939.7±104.8mLkg-1min-1 for the aCSF group and 1540.9±68.4mLkg-1min-1 for the 3mM CARB group, P<0.05) due largely to a decrease in respiratory frequency. GZA injection or CARB injection outside the LC (peri-LC) had no effect on ventilation under any conditions. The results suggest that gap junctions in the LC modulate the hypercapnic ventilatory response of adult rats. © 2013 Elsevier B.V.

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