The underestimated role of a somatosensory neural network on thyroid gland morphology: an experimental subarachnoid hemorrhage model study

Abstract

Objectives: Innervation of the thyroid gland has been attributed to the autonomic nervous system. Although peripheral sympathetic and parasympathetic innervations of the thyroid gland are well known, little is known about the somatosensory innervation of the thyroid gland. In this study, alterations on the somatosensory neural network of the thyroid gland following anexperimental subarachnoid hemorrhage were investigated in rabbits.Methods: Experiments were conducted on 23 rabbits under no medical intervention. Five rabbits were used as control group.Five rabbits were used as the sham group and serum physiologic (SF) was injected into their cisterna magna. The remaining 13animals were used as the subarachnoid hemorrhage (SAH) group; their own blood (1 ml) was re-injected into the cisterna magna.Thyroid hormone levels of animals were measured at the end of one month. Then, histological sections of the middle parts ofthe thyroid glands were stained with haematoxylin-eosin (H&E) for investigation of SAH-related damage. The total follicle volume (TFV) per cubic millimeter of the thyroid gland was estimated by stereological methods. Comparison of degenerated neuronal density (DND) in the C4 dorsal root ganglia (DRG) was examined bilaterally using H&E and TUNEL stainings.Results: Following SAH, neuronal degeneration in the cervical DRG caused somatic innervation deficiency, follicular atrophy andthyroid hormone depletion in the thyroid gland. T3 and T4 hormone levels of the SAH group (T3: 61±8 μg/dl; T4: 1.01±0.12μg/dl) were significantly (p