Oxytoxin is the hormone of social interactions, the mechanism of the interaction mostly unknown. Therefore, it is a nice surprise that Nakajima, Görlich, and Heintz from the Rockefeller Univ. in New York report in Cell on a newly identified subset of somatostatin interneurons from the prefrontal cortex of mice which bear the oxytocin receptor.
They silenced then this receptor in some mice. The females in these silenced mice with the oxytocin receptor inactive lacked the social interactions with male mice only during the estrus phase, when copulation would ensure progeny. The interactions with female mice were normal. In the diestrus phase interactions with males were not disturbed.
Similarily they could produce mice where the oxytocin gene was removed in the prefrontal cortex. The female mice showed the same deficit. Even mice treated with an oxytocin antagonist blocking the action of oxytocin had the same effect on the social interactions of the females thus treated.
We do not know whether oxytoxin is acting here in an endocrine way via the blood or as a neurotransmitter via synapses. It is not to far fetched to think oxytocin stimulating these interneurons is required – in mice – for social interactions leading to progeny although it is not in the paper.
A nice bit of information!
Almost any animal regulates its metabolism as well as its reproductive life according to the time of the year. (The fact that some domestic animals do not is the exception). This dependence on the season has long been a mystery for endocrinologists. Even then it was found that the Nucleus suprachiasmaticus in the hypothalamus controls and generates a circadian (daily) rhythm which is reflected in all animals analyzed the circannual (yearly) rhythm remained obcur.
Recent developments have shown that some pituitary cells in Pars tuberalis (PT; close to the pituitary stalk) measure the length of day via the melatonin they receive. Since melatonin is only produced in the dark, much melatonin means long nights and few melatonin means short nights. These cells therefore have been named calendar cells.
In an Open Access review in the Journal of Endocrinology Shona Wood and Andrew Loudon have summarized what is known about the physiology and biochemistry of this circannual regulation. They show that thyriod hormones and their conversion from thyroxine to triiodothyronine by deiodinase are an important part in the short day response. They analyse the melatonin response in the PT. They also show how clock genes are differential regulated during the seasons. Finally they show that a ancient gene, the eye absent protein 3 (EYA3) is specifically upregulated when the days get longer.
These genes are ancient and found in insects as well as in birds and mammals pointing to a very old mechanism.
Nice paper, worth studying!
Two reviews in Trends in Endocrinology and Metabolism (DOI: http://dx.doi.org/10.1016/j.tem.2014.05.001 and DOI: http://dx.doi.org/10.1016/j.tem.2014.03.013) address the development and the pathogenesis of pancreatic β-cells. Conrad, Stein and Hunter describe the transcription factors in mice and man which lead to β-cell genesis while Thomsem and Gloyn focus their attention to malfunction leading diabetes mellitus. Both reviews together show the actual status in β-cell research.
In a comment on a paper in the same issue of PNAS Sarina Saturn describes how Abraham et coworkers have analysed the complex relationship of neural activation, hormones and behaviour in first time parents comparing primary care /PC) mothers and secondary care (SC) fathers who are partners of mothers and primary care (PC) fathers who raise a child without a mother.
Abraham et al. have identified characteristic features common to fathers and mothers and, not surprisingly, also features where mothers and fathers differ. An emotional network including the amygdala (AMY),* ventral anterior cingulate cortex (vACC),* insula,* inferior frontal gyrus (IFG), and ventral tegmental area (VTA).* *Subcortical and paralimbic structures not located at the outer cortical surface was found as well as a mentalizing network which includes superior temporal sulcus (STS), frontopolar cortex (FPC), ventromedial prefrontal cortex (vmPFC), and temporal poles (TP). Cites from PNAS:
PC-mothers displayed the greatest activation of the emotional system, and this activation significantly related to parent–infant synchrony and oxytocin levels. SC-fathers, in contrast, exhibited more activation of the cortical system. Fascinatingly, PC-fathers showed amygdala activation similar to PC-mothers and STS activation similar to SC-fathers, with pronounced functional connectivity between the two regions. This suggests that when a baby is raised by PC-fathers, both systems are used for optimal childrearing.
For both PC-fathers and SC-fathers, the STS–amygdala overlap directly related to how much the men were involved in tending to the baby, and STS activation correlated with oxytocin levels and parent–infant synchrony. This provides evidence that exposure to the infants and caretaking activities can groom oxytocin and neural systems to carry out the degree of paternal involvement.
This is a first time that these interactions have been studied. Nicely done!