Key result
Hypophysectomy reduces maximum action potential spikes in adrenal chromaffin cells by ~50%.
Why the study?
The hypothalamic-pituitary-adrenocortical axis was found to control alternative splicing of BK channels in adrenal chromaffin cells, suggesting pituitary regulation of their electrical properties.
Absolute Event Rate: 4.88% vs 9.67%
p-value: p=<0.0001
Pituitary hormones regulate the intrinsic electrical properties of adrenal chromaffin cells by tailoring BK channel function, which may adapt the mechanics of adrenal catecholamine release.
Animal data link pituitary hormones to chromaffin excitability; leaves open human catecholamine regulation.
The discovery that the hypothalamic-pituitary-adrenocortical (HPA) endocrine stress axis controls an alternative splicing decision in chromaffin Slo-encoded BK (big potassium) channels raised the possibility that activation of the HPA could serve as a mechanism to tune the intrinsic electrical properties of epinephrine-secreting adrenal chromaffin cells. To test this, we compared BK functional properties and cell excitability in chromaffin cells from normal and hypophysectomized (pituitary-ablated) rats. Hypophysectomy was found to alter the voltage dependence and kinetics of BK gating, making channels less accessible for activation from rest. Perforated-patch recordings revealed changes in action potential waveform and repetitive firing properties. The maximum number of spikes that could be elicited with a 2 sec depolarizing current pulse was reduced by approximately 50% by hypophysectomy. The results indicate that pituitary hormones can adapt the mechanics of adrenal catecholamine release by tailoring BK channel function.
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Lovell et al. (2001) studied Adrenal chromaffin cell excitability (n=45). Hypophysectomy vs. Unoperated (normal) rats was evaluated on Maximum number of action potential spikes elicited by a 2-second depolarizing pulse (p=<0.0001). Hypophysectomy reduced the maximum number of action potential spikes elicited by a 2-second depolarizing pulse in adrenal chromaffin cells by approximately 50% (4.88 vs 9.67 spikes, p<0.0001).
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