London, Feb 3 (IANS) Scientists have pinpointed a mechanism for regulating prolactin, a hormone. The results may be significant for conditions and functions such as breast-feeding, sexual libido, and metabolism.
Prolactin is released from the pituitary gland in the brain and is the signal that triggers breast milk production during nursing. Prolactin plays important roles in reproduction and fertility, one of which is reduction of sexual libido.

It is believed that prolactin is significant for metabolism, since patients with elevated levels of prolactin can become overweight.

Levels of prolactin often rise in patients who are treated with dopamine inhibitors for psychotic disorders, and these patients often experience loss of libido and sometimes the production of breast milk as undesired effects.

The reason that women normally do not produce milk — and men never do — is that the release of prolactin is normally strongly inhibited by the signal substance dopamine. This is secreted by cells known as ‘TIDA’ neurons in the hypothalamus in the brain.

A research group at Karolinska Institutet has for the first time examined electrical activity of the dopamine-producing TIDA cells, in order to understand in depth the regulation of prolactin.

The study has shown that the cells normally display an extremely rhythmical activity, with discharges every 20 seconds.

The scientists believe that this rhythmical behaviour lies behind the ability of the TIDA cells to function as a strong inhibitor of prolactin release, says a Karolinska release.

“It is known that rhythmical signalling makes it possible for nerve cells to release large quantities of signal substances,” says Christian Broberger, who has led the study.

These findings are slated for publication in Neuron.