Changes of adrenoceptor-mediated responses in the pithed rat during propylthiouracil-induced hypothyroidism.
Adrenoceptor-mediated responses of the cardiovascular system during propylthiouracil-induced hypothyroidism were investigated. Interfering nervous reflexes could be circumvented by using pithed rats. Cardiac beta-adrenoceptor-mediated acceleration of heart rate following electrical stimulation or injection of noradrenaline and isoprenaline was markedly diminished even after 2 weeks of treatment. This loss of beta-sensitivity prevented the study of possible changes of presynaptic regulatory adrenoceptors in this test model. Taking the increase in diastolic blood pressure after application of alpha-agonists as index of the sensitivity of vascular alpha-adrenoceptors we found these to have been desensitized in the hypothyroid state. According to these results the lack of thyroid hormones exerted a similar effect on cardiac beta- and on vascular alpha-adrenoceptors.
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002046:Bupranolol / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D004195:Disease Models, Animal; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D007037:Hypothyroidism / Q000139:chemically induced / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011441:Propylthiouracil; D051381:Rats; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology; D014403:Tubocurarine / Q000494:pharmacology
D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D011441:Propylthiouracil; D001285:Atropine; D002046:Bupranolol; D007545:Isoproterenol; D003000:Clonidine; D014403:Tubocurarine; D009638:Norepinephrine