Dopamine D2 receptor stimulation with hypoxia has opposite effects on ventilation in hypothyroid and euthyroid hamsters

Hypothyroidism, a prevalent endocrine disorder, affects breathing, although the mechanisms involved are not well understood. Here we evaluated effects of a D2 receptor agonist, bromocriptine (1 mg/kg, B), on ventilation in conscious hypothyroid (H) and euthyroid (E) hamsters. Hypothyroidism was induced by propylthiourical in drinking water. Animals were treated with saline (S) or B dissolved in S and exposed to air, then to 10% O2 (hypoxia) for 5 minutes, and to air again. Ventilation of S‐treated H animals was lower than that of S‐treated E hamsters in all conditions. Treatment with B significantly decreased body temperature in H and E groups, but had no effect on ventilation when animals were initially exposed to air. During exposure to hypoxia, ventilation increased 34% in the H hamsters, but decreased 49% in E hamsters treated with B. A similar pattern was noted when hamsters were reoxygenated following exposure to hypoxia. Sham exposures to air using the same pattern as with B did not decrease ventilation in E hamsters. Thus, hypoxic stimulation is necessary to elicit opposite effects of D2 receptor stimulation in E compared to H hamsters. NIH Grant # 2 P20 RR‐016479