کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
2841181 | 1165382 | 2009 | 9 صفحه PDF | دانلود رایگان |
Stress-induced arrest of ventilatory motor pattern generation is tightly correlated with an abrupt increase in extracellular potassium concentration ([K+]o) within the metathoracic neuropil of the locust, Locusta migratoria. Na+/K+-ATPase inhibition with ouabain elicits repetitive surges of [K+]o that coincide with arrest and recovery of motor activity. Here we show that ouabain induces repetitive [K+]o events in a concentration-dependent manner. 10−5 M, 10−4 M, and 10−3 M ouabain was bath-applied in semi-intact locust preparations. 10−4 M and 10−3 M ouabain reliably induced repetitive [K+]o events whereas 10−5 M ouabain had no significant effect. In comparison to 10−4 M ouabain, 10−3 M ouabain increased the number and hastened the time to onset of repetitive [K+]o waves, prolonged [K+]o event duration, increased resting [K+]o, and diminished the absolute value of [K+]o waves. Recovery of motor patterning following [K+]o events was less likely in 10−3 M ouabain. In addition, we show that K+ channel inhibition using TEA suppressed the onset and decreased the amplitude of ouabain-induced repetitive [K+]o waves. Our results demonstrate that ventilatory circuit function in the locust CNS is dependent on the balance between mechanisms of [K+] accumulation and [K+] clearance. We suggest that with an imbalance in favour of accumulation the system tends towards a bistable state with transitions mediated by positive feedback involving voltage-dependent K+ channels.
Journal: Journal of Insect Physiology - Volume 55, Issue 7, July 2009, Pages 599–607