An integrative view of mammalian seasonal neuroendocrinology.

Seasonal neuroendocrine cycles that govern annual changes in reproductive activity, energy metabolism and hair growth are almost ubiquitous in mammals that have evolved at temperate and polar latitudes. Changes in nocturnal melatonin secretion regulating gene expression in the pars tuberalis (PT) of the pituitary stalk are a critical common feature in seasonal mammals. The PT sends signal(s) to the pars distalis of the pituitary to regulate prolactin secretion and thus the annual moult cycle. The PT also signals in a retrograde manner via thyrotropin stimulating hormone (TSH) to tanycytes, which line the ventral wall of the third ventricle in the hypothalamus. Tanycytes show seasonal plasticity in gene expression and play a pivotal role in regulating local thyroid hormone (TH) availability. Within the medio-basal hypothalamus, the cellular and molecular targets of TH remain elusive. However, two populations of hypothalamic neurons, which produce the RF-amide neuropeptides Kisspeptin and RFRP3, are plausible relays between TH and the GnRH-pituitary-gonadal axis. In contrast, the ways through which TH also impinges on hypothalamic systems regulating energy intake and expenditure remains unknown. Here, we review the neuroendocrine underpinnings of seasonality and identify several areas which warrant further research. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.