Evolvement of Oxytocin Pathway: Its Impact on Species’ Behavior

Examining the evolution of signalling factors is essential to understanding how hormones work to coordinate and control the activities in vertebrates. Oxytocin is a hormone that is commonly associated with contractions during labour and the lactation process post labour. It is also associated with many parts of the reproductive tract, as well as reproductive and social behaviour. In basal vertebrate, the location of the neurons in the pathway and the behaviour responses are much simpler and primitive. Whereas in advanced vertebrate there is a shift in the neuron location and which develops an axonal branching system that makes it more complex and therefore modifies behavioural response (Knobloch et al. 2014). Here, it is depicted how the classical oxytocin pathway evolved into a much more sophisticated process and how behaviour has evolved based on this pathway and conditions of different species. Oxytocin is produced in the magnocellular neurosecretory cells in the brain. These cells are found in different nucleuses depending on where a species is in respect to the phylogenetic tree.

For more primitive vertebrates, they are found randomly distributed throughout one nucleus which inhabits the third ventricle of the hypothalamus and releases oxytocin into the cerebrospinal fluid. As vertebrates evolved, the common location for the magnocellular neurosecretory cells split into two main nucleuses and with an accessory nucleus somewhere between them (Armstrong 1995). This changed where the release occurred and therefore species were able to prioritize the release of oxytocin to be more beneficial. During the evolution of reptiles, the separation of the primitive nucleus coincided with the development of the forebrain, suggesting that the forebrain restricted the movement of the magnocellular neuron cells forcing them to adapt. Instead of moving the cell and nucleus into the forebrain, it kept away from the third ventricle and formed dendritic trees and new axonal projections. With these new adaptations, the oxytocin could reach different regions of the forebrain to make responses more complex (Knobloch et al. 2014). This meant that the pathway was dominated by a vascular release and no longer by a release into the cerebrospinal fluid. Species who demonstrate the primitive pathway seem to show slow responses that are expected and not complex. As species evolved they needed more diverse social behaviours at a faster rate to survive.

The vascular release meant that organisms could quickly modify the activity of certain brain regions and therefore express more dynamic responses, such as a father developing a sense of responsibility to share food with their young offspring to increase their chance at survival (Saito et al. 2011). Looking specifically at the human relation to the oxytocin pathway, there is an association with certain genes that are used to show empathy, control parenting behaviour and utilize social relationships to handle stress. These genes show polymorphic variation based on ethnic background and environmental conditions. In the case of psychopathology, there is a lack of parenting behavior and stress management which leads to the absence of basic human behaviour (Feldman et al. 2016). Development of these genes have evolved from the need for basic human behaviour therefore increasing their chance at survival.

To conclude, the primitive method was much less impactful than the branching axonal system we see in more advanced vertebrate. Thus, influencing the cognitive process which vertebrate use to express stronger social and reproductive behaviour. With the evolvement of the oxytocin pathway, species live their lives dynamically and more successfully.