Naloxone stimulates oxygen consumption but not ventilation in hypothyroid hamsters

Hypothyroidism stimulates D2 receptor-mediated breathing in response to acute hypoxia and alters D2 receptors levels in carotid bodies and brain

“…These results concur with previous findings in hypothyroid hamsters (Schlenker and Schultz, 2011) and rats (Peterson et al, 2006). This decreased ventilation may be the result of lower body temperatures and metabolic rates observed in the hypothyroid animals (Schlenker, 1994). Moreover, we observed similar results of Olea and coworkers (Olea et al, 2007) who showed that hypothyroid rats exhibited diminished carotid body hypoxic sensitivity relative to that noted in euthyroid animals.…”

“…For both studies respiratory measurements were made in hamsters placed into a 20.2 × 7.9 cm Plexiglas cylindrical chamber using the barometric method (Schlenker, 1984). Ports allowed air or 10% oxygen in nitrogen (hypoxia) to enter and exit the chamber.…”

“…In some cases thyroid hormone therapy reverses these dysfunctions, but not always (Jha et al, 2006; Misiolek et al, 2007). At the molecular level, thyroid hormones affect the expression and phosphorylation of various enzymes and the expression of pumps, channels and neurotransmitter systems that may affect ventilation including opioids, serotonin, gamma amino butyric acid, and dopamine (Burton and Kazemi, 2000; Diez et al, 2008; Kulikov and Zubkov, 2007; Sarkar et al, 2006; Schlenker, 1994; Slotkin and Slepetis, 1984; Varney and Schlenker, 2007). …”

Thyroid status affects 5-HT2Areceptor modulation of breathing before, during, and following exposure of hamsters to acute intermittent hypoxia

“…Since we have used the animal models in previous studies (50,51), we assumed that they would exhibit similar thyroid hormone abnormalities. Moreover, thyroid hormone measurements on PTU-treated and BIO 14.6 hamsters in a separate study indicated depressed thyroid function with low T 3 levels in the dystrophic hamsters (unpublished observations).…”

“…BIO 14.6 dystrophic hamsters exhibit lower ventilatory responses to hypoxia and hypercapnia, as well as lower O 2 consumption, and CO 2 production relative to the control hamsters (48). Previous research indicates that golden Syrian hamsters made hypothyroid by the administration of propylthiouracil (PTU) also exhibit lower ventilatory responses to hypoxia compared with euthyroid hamsters (50). Moreover, thyroxine supplementation in dystrophic hamsters was able to normalize their ventilatory responses to hypoxia (49).…”