@entity750 receptor subtypes required for ventilatory long-term facilitation and its enhancement after chronic intermittent @entity519 in awake XXXX .

@entity1088 @entity3858 @entity519 @entity1576 @entity750 @entity35 @entity6009
Respiratory long-term facilitation (LTF), a @entity750 -dependent, persistent augmentation of @entity1576 after @entity519 , is enhanced by pretreatment of chronic intermittent @entity519 (CIH; 5 min 11-12% O2-5 min air, 12 h/night for 7 nights). The present study examined the effects of @entity3858 ( @entity750 5-HT1,2,5,6,7 receptor antagonist), @entity6009 (5-HT2 antagonist), or @entity1088 (5-HT2,6,7 antagonist) on both ventilatory LTF and the CIH effect on ventilatory LTF in conscious male adult @entity35 to determine which specific receptor subtype(s) is involved. In untreated @entity35 (i.e., animals not exposed to CIH), LTF, induced by five episodes of 5-min poikilocapnic @entity519 (10% O2) separated by 5-min normoxic intervals, was measured twice by plethysmography. Thus the measurement was conducted 1-2 days before (as control) and approximately 1 h after systemic injection of @entity3858 (1 mg/kg ip), @entity6009 (1 mg/kg), or @entity1088 (1.5 mg/kg). Resting ventilation, metabolic rate, and @entity519 ventilatory response (HVR) were unchanged, but LTF ( approximately 18% above baseline) was eliminated by each drug. In CIH-treated @entity35 , LTF was also measured twice, before and approximately 8 h after CIH. Vehicle, @entity3858 , @entity6009 , or @entity1088 was injected approximately 1 h before the second measurement. Neither resting ventilation nor metabolic rate was changed after CIH and/or any drug. HVR was unchanged after @entity3858 and @entity6009 but reduced in four of seven @entity1088 @entity35 . The CIH-enhanced LTF ( approximately 28%) was abolished by @entity3858 and @entity1088 but only attenuated by @entity6009 (to approximately 10%). Collectively, these data suggest that ventilatory LTF requires 5-HT2 receptors and that the CIH effect on LTF requires non-5-HT2 @entity750 receptors, probably 5-HT6 and/or 5-HT7 subtype(s).
