Biol 499E

Advisor: Dr. Erlichman

SLU Festival of Science 2001 Poster Presentation

 

The brain stem consists of chemosensitive and nonchemosensitive regions. Chemosensitive areas in the brain stem are known to regulate ventilation in response to acidification by CO₂.  Acidosis of chemosensitive areas results in cellular depolarization causing neuronal firing, which increases ventilation through increased activation of the pre-Botzinger complex.  In one chemosensitive site, the NTS, adjacent neurons are linked through low resistance gap junctions.  It has been hypothesized that electrical coupling between chemosensitive areas may permit rapid synchronization of neural circuits involved in ventilatory control.  Using a push-pull cannula, placed unilaterally into the NTS, I wished to examine the ventilatory effect of disrupting electrical coupling focally in the conscious rat.  Electrical synapses were blocked using the specific gap junction inhibitor, carbenoxolone.  To evaluate the effects of carbenoxolone on central chemoreceptive sensitivity, I exposed the rat to progressive hypercapnia while measuring ventilation in a whole-body plethsmograph.  Inhibition of the gap junctions through elimination of electrical coupling decreased ventilation at all CO₂ concentrations.  Furthermore, the inhibition of ventilation with carbenoxolone appeared to be age dependent.  Older rats exposed to carbenoxolone showed no inhibition of ventilation.  These data suggest that the electrical synapses are important during development of CO₂ chemoreception, however the function of electrical coupling in central ventilatory control wanes with age.