Evidence for functional CB1 cannabinoid receptor expressed in the rat thyroid

Area of Science:

• Endocrinology
• Neuroscience
• Pharmacology

Background:

• Previous research indicates Delta(9)-tetrahydrocannabinol (Delta(9)TCH), a major marijuana component, can inhibit thyroid hormonal activity.
• Understanding the role of cannabinoid receptors in thyroid function requires detailed characterization of their expression and activity.

Purpose of the Study:

• To investigate the functional expression of the CB1 cannabinoid receptor in the rat thyroid gland.
• To determine the impact of cannabinoid receptor activation on thyroid hormone levels in rats.

Main Methods:

• Quantitative RT-PCR was used to assess CB1 receptor and fatty acid amide hydrolase mRNA expression in rat thyroid tissue.
• Western blot analysis detected the presence of CB1 receptor protein.
• Immunohistochemistry localized CB1 receptor expression within thyroid cells. Serum hormone levels were measured after administration of a CB1 agonist and antagonist.

Main Results:

• CB1 receptor and fatty acid amide hydrolase mRNA were detected in rat thyroid tissue.
• CB1 receptor protein was identified, with positive staining in follicular and parafollicular cells.
• Administration of a CB1 agonist decreased serum thyroxine (T4) and tri-iodothyronine (T3) levels by 30%, an effect blocked by a CB1 antagonist. Thyrotrophin levels remained unaffected.

Conclusions:

• Functional CB1 receptors are expressed in the rat thyroid gland.
• These receptors are capable of modulating the release of thyroid hormones T3 and T4.
• Cannabinoids may play a significant role in the physiological regulation of rat thyroid hormonal activity.