Effects of hypothyroidism in female hamsters on D1 receptor modulated breathing and expression of D1 receptors (1178.2)

Abstract

The D1 receptor antagonist, SCH23390 (SCH), decreased ventilation (VE) in euthyroid (E) male hamsters exposed to air and hypoxia, but increased VE in hypothyroid (H) hamsters exposed to air, but not during hypoxic exposures. In H relative to E males, D1 receptor expression was decreased in the carotid body (CB), striatum, and paraventricular nucleus of the hypothalamus (PVN), but not in the nucleus tractus solitarius (NTS). For the present study we hypothesized that in H female hamsters D1 receptor expression in the CB, PVN, NTS and striatum and modulation of breathing would be dissimilar to that observed in H males. H and E female hamsters received SCH or saline. Physiological parameters were evaluated in awake animals exposed to air, 5 minutes of hypoxia (10% O2 in N2) and then air. SCH decreased body temperatures in both groups, had no effect on metabolism, but VE was increased in the H hamsters relative to E hamsters’ responses during air and hypoxic exposures due to increased tidal volumes. SCH relative to saline decreased breathing frequency, but increased tidal volume in the E hamsters during baseline and post‐hypoxic air exposures. In both groups SCH decreased hypoxic responsiveness. Expression of D1 receptors was similar in both groups in all regions. Thus, the ventilatory responses in H females were similar to SCH relative to H males (but not in E males), expression of D1 receptors was dissimilar in 3 regions.Grant Funding Source: Internal Sanford School of Medicine Grant