Question

In seasonal breeders (e.g., sheep), an increase in melatonin

A) occurs in the summer.
B) causes the anterior pituitary to release luteinizing hormone.
C) increases the sensitivity of the pituitary gland to negative feedback.
D) corresponds with a reduction in fertility.

Answer 1

Melatonin production in seasonal breeders like sheep increases during darker periods and corresponds with a reduction in fertility by inhibiting reproductive functions.

Step-by-step explanation:

In seasonal breeders, such as sheep, an increase in melatonin usually corresponds with a reduction in fertility. Melatonin production is influenced by the amount of light and increases during the dark periods. The pineal gland is responsible for melatonin production, which has an inhibitory effect on reproductive functions by decreasing the production and maturation of reproductive cells and organs. Especially during the night, an increase in melatonin can lead to lower levels of the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are necessary for reproductive functions.

Melatonin's role as an antioxidant protecting the CNS is also significant, but this has less to do with the question regarding seasonal breeding and fertility. It is also worth noting that in children, higher levels of melatonin might inhibit the onset of puberty by preventing the release of gonadotropins from the anterior pituitary.