Does a Melatonin-Dependent Circadian Oscillator in the Pars Tuberalis Drive Prolactin Seasonal Rhythmicity?
Article first published online: 2 JUN 2007
Journal of Neuroendocrinology
Volume 19, Issue 8, pages 657–666, August 2007
How to Cite
Dardente, H. (2007), Does a Melatonin-Dependent Circadian Oscillator in the Pars Tuberalis Drive Prolactin Seasonal Rhythmicity?. Journal of Neuroendocrinology, 19: 657–666. doi: 10.1111/j.1365-2826.2007.01564.x
- Issue published online: 22 JUN 2007
- Article first published online: 2 JUN 2007
- Received: 7 February 2007, revised 27 March 2007, accepted 3 April 2007
- pars tuberalis;
- clock genes
The pars tuberalis (PT) of the adenohypophysis expresses a high density of melatonin receptors and is thought to be a crucial relay for the actions of melatonin on seasonal rhythmicity of prolactin secretion by the pars distalis (PD). In common with the suprachiasmatic nucleus of the hypothalamus and most other peripheral tissues, the PT rhythmically expresses a range of ‘clock genes’. Interestingly, this expression is highly dependent upon melatonin/photoperiod, with several aspects unique to the PT. These observations led to the establishment of a conceptual framework for the encoding of seasonal timing in this tissue. This review summarises current knowledge of the morphological, functional and molecular aspects of the PT and considers its role in seasonal timing. The strengths and weaknesses of current hypotheses that link melatonin action in the PT to its seasonal effect on lactotrophs of the PD are discussed and alternative working hypotheses are suggested.