Sexual arousal: the main thing is to direct potassium ions in the right direction

The courtship ritual of rats is obscenely simple. When a male eager for sex touches the sides of a female ready for copulation, the "lordosis reflex" is triggered in the female: she bends her back, raises her tail and stands motionless, allowing the excited male to take the position from above.

Scientists at Rockefeller University (New York), working under the guidance of Dr. Donald Pfaff, have deciphered the exact physico-chemical process taking place in a group of brain cells that control this reflex – ventromedial hypothalamic neurons.

In earlier works, Pfaff's group studied in detail the neural and hormonal mechanisms of regulation of reflex lordosis. The aim of their new research was to decipher the mechanisms of this process at the molecular and cellular level.

All neurons, regardless of their location, maintain a constant flow of charged ions through the cell membrane, carried out through ion channels – proteins immersed in the membrane, having the shape of a bagel. An increase or decrease in the concentration of any compounds in brain cells affects the movement of ions into and out of the cell by closing or opening ion channels. Scientists have long known that the neurotransmitter norepinephrine, which increases mindfulness and participates in stress reactions, excites ventromedial hypothalamic neurons, but it remained unknown how and which ions it affects.

Using the method of cell potential fixation, the authors found that norepinephrine prevents the release of potassium ions from these cells by blocking the rapid flow of A-type potassium, which leads to their activation. When potassium ions accumulate, the cell generates electrical impulses that trigger all subsequent links of the signaling cascade, forcing female rats to bend their backs.

Moreover, researchers have demonstrated that pre-administration of the female sex hormone estradiol to animals leads to an increase in the number of cells responding to norepinephrine, which increases the need for copulation. Apparently, estradiol activates a complex of genes necessary for the expression of the norepinephrine receptor.

The authors believe that, in addition to the activation of ventromedial hypothalamic neurons, norepinephrine performs a lot of functions in the mechanisms of stimulation of sexual behavior. According to Pfaff, through the action of norepinephrine on the ventromedial hypothalamic neurons, the general arousal of the animal contributes to the emergence of sexual arousal, which in turn forms a special behavior, without which reproduction is impossible.

Article by Lee et al. "Estradiol modulation of phenylephrine-induced excitatory responses in ventromedial hypothalamic neurons of female rats" published in Proceedings of the National Academy of Sciences.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily

17.06.2008