Age and hypothyroidism affect dopamine modulation of breathing and D₂ receptor levels.
During and following hypoxic exposure young male hypothyroid hamsters treated with the dopamine D(2) receptor agonist bromocriptine increased breathing, while ventilation was depressed in bromocriptine-treated euthyroid hamsters. Moreover, D(2) receptor expression was increased in carotid bodies and striatum, but not in the nucleus tractus solitaries (NTS) of hypothyroid relative to euthyroid hamsters. Here ventilation was determined in older male hypothyroid and euthyroid hamsters given vehicle or bromocriptine, and exposed to baseline air, hypoxia, and then air. Bromocriptine without hypoxia served as a time control. Relative to vehicle, bromocriptine depressed ventilation in both groups exposed to air or to hypoxia, but hypothyroid bromocriptine-treated hamsters increased ventilatory responsiveness to hypoxia, while euthyroid hamsters decreased ventilatory responsiveness to hypoxia and exhibited post-hypoxic depression. Hypothyroidism had no effect on D(2) receptor expression in carotid bodies or striatum, but increased it in the NTS. Thus, in hamsters bromocriptine modulates breathing and expression of D(2) receptor depending on the length of hypothyroidism.
Basic Biomedical Sciences, Sanford School of Medicine of University of South Dakota, United States.
Cory
C
Sykora
Mitch
M
Amor
Evelyn
E
Schlenker
D000375:Aging; D000704:Analysis of Variance; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D001971:Bromocriptine / Q000494:pharmacology; D002344:Carotid Body / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D006224:Cricetinae; D004298:Dopamine / Q000494:pharmacology*; D018491:Dopamine Agonists / Q000494:pharmacology; D007037:Hypothyroidism / Q000473:pathology / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D012123:Pulmonary Ventilation / Q000187:drug effects; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012119:Respiration / Q000187:drug effects*; D017552:Solitary Nucleus / Q000378:metabolism; D013961:Thyroid Gland / Q000187:drug effects / Q000473:pathology
D018491:Dopamine Agonists; D017448:Receptors, Dopamine D2; D001971:Bromocriptine; D004298:Dopamine