Because metabolism is a determinant of the ventilatory chemosensitivity, we tested the hypothesis that the ventilatory response to acute and prolonged @entity2944 is adjusted to the circadian oscillations in @entity26 consumption (VO2). Adult @entity35 were instrumented for measurements of body temperature (T(b)) and activity by telemetry. Pulmonary ventilation (VE) was measured by the barometric method and VO2 by the flow-through method. In the acute experiments, 16 conscious @entity35 entrained to a 12:12-h light (L)-dark (D) cycle (lights on 7:00 AM) were exposed to air, 2%, and then 5% @entity515 in normoxia (30-45 min each) at 11:00 AM and 11:00 PM. In a separate group of seven @entity35 , simultaneous recordings of all variables were made continuously for 3 consecutive days in air followed by 3 days in 2% @entity515 in normoxia, in a 12:12-h L-D cycle (lights on 7:00 AM). In air, all variables were significantly higher at night, whether @entity35 were studied acutely or chronically. Acute @entity515 exposure had similar significant effects at 11:00 AM and 11:00 PM on VE (approximately 25 and 100% increase with 2 and 5% @entity515 , respectively) and @entity4962 (approximately 8% drop with 5% @entity515 ), such that the hyperventilatory response (% increase in VE/VO2 from air) was similar at both times. Chronic @entity515 breathing increased VE at all times of the day, but less so during the L phase (approximately 15 vs. 22% increase in L and D, respectively), when activity was lower. However, VO2 was reduced from the air level (approximately 10% drop) in the L, such that the VE/VO2 response was similar between L and D. The same result was obtained when the VE/VO2 response was compared between the L and D phases for the same level of activity. These results suggest that, throughout the day, the hypercapnic hyperpnea, whether during acute or prolonged @entity515 , is perfectly adjusted to the metabolic level.

Circadian pattern of ventilation during acute and chronic XXXX in conscious adult @entity35 .

@entity4962 :: ('CHEBI:30046', 'Chemical') :: ['VO2'] @entity2944 :: ('MESH:D006935', 'Disease') :: ['hypercapnia'] @entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity515 :: ('CHEBI:29334', 'Chemical') :: ['CO2'] @entity35 :: ('10116', 'Species') :: ['rats']
@entity2944 :: (MESH:D006935,Disease) :: ['hypercapnia']
