Title

Thyroid and Thyroxine Effects on Adrenoreceptors in Relation to Circadian Activity

Document Type

Article

Language

eng

Format of Original

6 p.

Publication Date

9-1993

Publisher

Elsevier Inc.

Source Publication

Pharmacology Biochemistry and Behavior

Source ISSN

0091-3057

Original Item ID

DOI: 10.1016/0091-3057(93)90349-X

Abstract

Experiments were conducted to ascertain if changes in central adrenergic receptors could be associated with altered circadian activity patterns induced by thyroparathyroidecomy (TPX) and thyroxine. An initial experiment used TPX and sham-operated rats that had been exposed to dim red light for 7 months. The α and β receptor densities were compared in the suprachiasmatic nuclei (SCN), preoptic (PO), septum, and caudate-putamen. TPX animals showed significant reductions in β1 and β2 receptor densities in SCN and PO, and α1 densities in SCN, but no other changes A second experiment, lasting 4 months, examined the effects of thyroxine, which has been shown to reverse the period-shortening effects of TPX surgery. Thyroxine signicantly increased β1 receptors in both the SCN and ventromedial hypothalamus (VMH), the only regions that displayed significant reductions in TPXs during the second experiment. Increases of sevenfold and threefold were observed in the SCNs of TPXs and sham, respectively, but thyroxine's action in the VMH was limited to TPX animals, an affect that mimics thyroxine's antion on circadian activity rhythms.

Comments

Pharmacology Biochemistry and Behavior, Vol. 46, No. 1 (September 1993): 251-257. DOI. © 1993, Elsevier Inc.

Dr. Robert Molthen was affiliated with University of Pennsylvania at the time of publication.