Abstract
We reported the effects of 5-hydroxytryptamine 2 (5-HT2) receptor activities in the dorsomedial medulla oblongata (DMM) on airway resistance and ventilation in mice. We compared perfusion of a selective serotonin reuptake inhibitor, fluoxetine, and the co-perfusion of fluoxetine plus a 5-HT2 receptor antagonist, LY-53857, in a double-chamber plethysmograph. The results suggested that 5-HT2 receptor activity in the DMM determines the set points for both airway dilation and ventilatory volume that are suited to the facilitated respiratory drive. We also found that the mice we placed in the double-chamber plethysmograph spent a lot of time awake. In the present study, we examined basal activity of the 5-HT2 receptors in the DMM to airway resistance without background stimulated by fluoxetine. Each mouse was anesthetized intraperitoneally with pentobarbital sodium and the medulla oblongata exposed dorsally. A microdialysis probe (CUP7; membrane length, 1 mm) was inserted into the DMM and fixed to the cranial bone. The skin incision was closed. Each mouse was placed in a double-chamber plethysmograph. After recovery from anesthesia, airway resistance obtained by single perfusion of 10−5 M LY-53857 was compared with that obtained by artificial cerebrospinal fluid. The preliminary experiments showed that a single perfusion of LY-53857 tended to increase airway resistance. As well, we discuss basal activity of 5-HT2 receptors in the DMM in respect to airway resistance. [J Physiol Sci. 2007;57 Suppl:S213]
