Changes in dopamine D2-receptor modulation of the hypoxic ventilatory response with chronic hypoxia

Modulation of the hypoxic ventilatory response (HVR) by dopamine D-2-receptors (D-2-R) in the carotid body (CB) and central nervous system (CNS) are hypothesized to contribute to ventilatory acclimatization to hypoxia. We tested this with blockade of D-2-R in the CB or CNS in conscious rats after 0, 2 and 8 days of hypoxia. On day 0, CB D-2-R blockade significantly increased (V) over dot I and frequency (fR in hyperoxia (FIO2 = 0.30), but not hypoxia (FIO2 = 0.10). CNS D-2-R blockade significantly decreased fR in hypoxia only. On day 2, neither CB nor CNS D-2-R blockade affected (V) over dot I or fR. On day 8, CB D-2-R blockade significantly increased hypoxic (V) over dot I and fR. CNS D-2-R blockade significantly decreased hypoxic (V) over dot I and fR, CB and CNS D-2-R modulation of the HVR decreased after 2 days of hypoxia, but reappeared after 8 days. Changes in the opposing effects of CB and CNS D-2-R on the HVR during chronic hypoxia cannot completely explain ventilatory acclimatization in rats. (C) 2000 Elsevier Science B.V. All rights reserved.