Role of the pyramidal tract in the mechanism of dyspnea and hyperventilation

: Phentolamine, a blocker of alpha-adrenoceptors, given in a single dose (one hour before or 30 minutes, 8 and 24 hours after liver resection) decreased the mitotic index and the coefficient of mitotic phases, and elevated the glycogen content. The number of two-nucleated cells in rats exposed to phentolamine rose 8 hours after resection (p < 0.05). Obsidan, a blocker of beta-adrenoceptors, administered at the same periods, increased the mitotic index and the coefficient of mitotic phases. It is suggested that phentolamine prolonged the late mitotic phases, inhibiting the entry of the cells into mitosis. Obsidan elicited an opposite effect.