Sensitivity of the hyperthyroid and hypothyroid mouse to histamine and 5-hydroxytryptamine

Area of Science:

• Endocrinology
• Pharmacology
• Physiology

Background:

• Thyroid hormones, such as thyroxine, play a crucial role in regulating metabolic rate and physiological responses.
• Histamine and 5-hydroxytryptamine are key biogenic amines involved in various biological processes, including allergic reactions and neurotransmission.
• The interplay between thyroid hormones, adrenal hormones, and biogenic amine sensitivity is not fully elucidated.

Purpose of the Study:

• To investigate the effect of thyroxine sodium administration on the sensitivity of mice to histamine and 5-hydroxytryptamine.
• To examine the modulatory role of hydrocortisone and anti-thyroid drugs on thyroxine-induced changes in biogenic amine sensitivity.
• To explore the relationship between metabolic rate, adrenal gland function, and histamine sensitivity following thyroxine treatment.

Main Methods:

• Mice were injected with thyroxine sodium, and their sensitivity to histamine and 5-hydroxytryptamine was assessed.
• Concurrent administration of hydrocortisone or anti-thyroid drugs was employed to evaluate their antagonistic or synergistic effects.
• Metabolic rate was measured, and changes in adrenal gland size and function were observed during prolonged thyroxine treatment.

Main Results:

• Thyroxine sodium injections significantly increased mouse sensitivity to histamine, peaking at 6 days.
• A lesser increase in sensitivity to 5-hydroxytryptamine was observed.
• Hydrocortisone counteracted the effect of thyroxine on histamine sensitivity, while anti-thyroid drugs alone reduced it.
• Thyroxine treatment elevated metabolic rate, also peaking at 6 days.
• Prolonged thyroxine administration led to adrenal gland enlargement, suggesting a role in the subsequent decline of histamine sensitivity.

Conclusions:

• Thyroxine administration enhances sensitivity to histamine and, to a lesser degree, 5-hydroxytryptamine in mice.
• Adrenal hormones, particularly those influenced by hydrocortisone, can antagonize thyroxine's effects on biogenic amine sensitivity.
• Changes in metabolic rate and adrenal function are closely linked to the observed alterations in histamine sensitivity following thyroxine treatment.