During this reaction, certain hormones like adrenalin and cortisol are released, speeding the heart rate, slowing digestion, shunting blood flow to major muscle groups, and changing various other autonomic nervous functions, giving the body a burst of energy and strength. This is the bodyвЂ™s response to perceived threat or danger. The sympathetic nervous system releases hormones that cause changes to occur throughout the body. The fight or flight response refers to a specific biochemical reaction that both humans and animals experience during intense stress or fear. Understanding our body's natural response to threat and danger can help us better understand the symptoms of PTSD.

The difference between anxiety and fearД®veryone, especially military personnel, are going to encounter some kind of stressful or dangerous situation in their lifetime, and fortunately, our body has a natural, built-in stress response to threatening situations called the вЂfight or flight responseвЂ™.

This behavioural strategy could serve as a stress buffer for the animals,' said Glenk. 'It is particularly interesting that physical contact increased during anoestrus under the strong increase of cortisol. The results show a considerable influence of sexual cycle phase on stress hormones as well as social and flight behaviour. There was only a marginal increase in the release of testosterone in both cycle phases.

Furthermore, blood concentrations of the hormone cortisol before the experiment were lower in unreceptive animals, but significantly rose during the confrontation. Peaceful 'sitting together' was only observed during anoestrus. When they were in heat, however, the animals fled from their competitors significantly more often.

the phase in which the animals are able to reproduce, which starts with the temporary partial rupture of the vaginal closure membrane, and anoestrus during which the membrane remains closed until the next fertile period.ДЇrom the behavioural observations and laboratory results, the researchers concluded that aggressive behaviour occurred independently of the sexual cycle. Together with her colleagues from the Department of Behavioural Biology of the University of Vienna, Glenk observed the female guinea pigs at two different times of the cycle: oestrus, i.e. 'To gain a better understanding of how sexual and stress hormones modulate behaviour, we confronted guinea pigs with an unknown female conspecific in an experimental arena,' said the lead author. Stress hormones play a key role in this process because they mobilise energy for flight or fight in the body. Animals with a good intuition of when to compete or withdraw are more successful and better integrated,' explained Lisa-Maria Glenk from the Unit of Comparative Medicine of the Messerli Research Institute. Such hierarchies are established through confrontations between conspecifics. 'These rodents live in social hierarchies, similar to many other mammals. So far, there has been hardly any research on the influence of the 'hormonal rollercoaster' on the social behaviour of female guinea pigs. Hormonal rollercoaster determines behaviour The results clearly indicate that females tend to flee from one another during their fertile periods, but outside these periods they risked the confrontation. These variations, caused by the rhythm of oestrus and anoestrus, may influence the social behaviour of the rodents given that guinea pigs naturally maintain a hierarchy in which dominant animals take advantage.ДЄ research team from the University of Veterinary Medicine, Vienna, and the University of Vienna analysed social behaviours and hormone levels to find out how female guinea pigs are affected by the oestrus cycle during the encounter with a female conspecific. Also in female guinea pigs, Cavia porcellus, hormone levels fluctuate with fertility.

Fight or flight hormones