Shalini Kumar Palathinkal
Did you know that among animals, especially rodents like mice and rats, the females decide when they are ready for some action? You know what I mean … wink, wink. That’s right, the female rodents decide when, and with which male, they want to mate to produce offspring. And this decision is made with the help of a particular type of neuron in the brain that is essential for maintaining fertility, called kisspeptin.
Thus, unlike in humans, the need for mating is prompted in most mammals only around the time of ovulation. This ensures the highest chance of fertilisation. Particularly in rodents, the female controls the initiation and timing of copulatory contacts with the male, triggering the mate preference and sexual motivation circuit in their brains. However, what controls the neural circuitry to drive the female rodents to be suddenly sexually receptive to the males, in comparison to when they are not, remains elusive. An international team of researchers led by Dr Julie Bakker from GIGA Neurosciences, University of Liege, Belgium in 2018 may have some answers to this intriguing question.
Kisspeptin is a neuropeptide (a small protein-like molecule used by neurons to communicate with each other) encoded by the KISS1 gene. It is secreted from a distinct type of neuronal population (kisspeptin neurons) found in our brain. In animals and humans this hormone is essential for the onset of puberty and, by controlling the process of ovulation, for maintaining fertility. The lack of this hormonal action can lead to infertility, delayed onset of puberty, and a less developed and unviable reproductive system. Interestingly, in comparison to their male counterparts, females exhibit a greater number of kisspeptin neurons. This suggests a crucial role for these neurons in the female reproductive system.
The 2018 Belgian study looked at kisspeptin’s role in sexual receptivity in females. The study was inspired by scientific evidence that male pheromones, and not female pheromones, could activate the kisspeptin neurons in female mice. (Pheromones are chemicals secreted by an individual that are capable of acting outside the body to influence the behaviour of a receiving individual.) The researchers wanted to tease out the neural circuitry that controls reproduction and sexual receptivity. By specifically ablating, or killing, the kisspeptin neurons in the female mice brains, the researchers demonstrated that these neurons were important in eliciting the females’ sexually receptive behaviours towards males, behaviours that favoured sexual activity and successful fertilisation. Using several cutting-edge technologies, they provided the first evidence for the essential ‘central-hub’ role played by kisspeptin neurons in governing and orchestrating sexual behaviour in female mice.
The researchers in this study believe that therapeutics targeting kisspeptin signalling may hold treatment potential for conditions that manifest with low sexual desire in women, including hypoactive sexual desire disorder (HSDD).
The story of what the Belgian researchers discovered is also a story about how scientific knowledge progresses. Their study has been a powerful influence on my own recent research, in Otago, into the regulation of the initiation of labour in pregnancy. More on that to come!
Shalini Kumar Palathinkal recently finished her PhD in Neuroendocrinology at the Centre for Neuroendocrinology, Department of Physiology, University of Otago and is awaiting her graduation. She is passionate about communicating science to the wider community and is a freelance Science Writer. She loves to spend time reading, writing, painting and gardening, and is also devoted to teaching her Kiwi-accent daughter their native language, Malayalam.
For more by Shalini Kumar Palathinkal on Corpus, see What’s cooking in physiology research? Towards Safer Births