Specific and Non-Specific Thalamocortical Afferents to the Whisker–Related Sensory Cortical Region in Rats with Congenital Hypothyroidism


1 Ph.D. of Physiology, Neuroscience Research Center, Institute of Pharmachology, Kerman University of Medical Sciences, Kerman, Iran & School of Medicine, Shahid Beheshti University of Medical Sciences,Tehran, Iran

2 Professor of Physiology, School of Medicine & Functional Neuroanatomy Laboratory, Neurophysiology Research Center, Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran


Background & Aims: Thyroid hormones are of great importance in the development of the central nervous
system. Congenital hypothyroidism may affect the reorganization of specific and non-specific
thalamocortical afferents to whisker–related sensory (wS1) corticol region in rats.
Methods: Congenital hypothyroidism was induced by adding propylthiouracil (PTU) (25 ppm) to the rats’
drinking water from embryonic day 16 to postnatal day 60. Pregnant rats were divided into normal and
congenital hypothyroidism groups. Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was
injected into wS1 cortical area as tracer.
Results: Following tracer injection, retrogradely labeled neurons were observed in the thalamic specific
relay nuclus including ventral posterior medial (VPM), and in the nonspecific thalamic nuclei including
centrolatral (CL), centromedial (CM), ventromedial (VM), posteromedial (PO), and reunion (Re). The
number of VPM and PO labeled neurons significantly reduced in the congenital hypothyroidim group
compared to the normal group (P < 0.01 and P < 0.05, recpectively). No significant difference was observed
between the hypothyroidism group and control group in terms of the number of labeled projection neurons in
CL, CM, VM, and Re nuclei.
Conclusion: The present study showed that congenital hypothyroidism alters the thalamocortical projection
pattern from VPM and PO thalamic nuclei to barrel cortex


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