Thanks, Dr. Patil, sounds interesting it was a big question in my mind for a long time.

Interesting, @Masoume,

I spent some 9 years of my researcher activities, trying to unfold such problems, as I chose the Wistar rat as an anatomical model to understand the microvascular aspects of hormonal changes in the female genital system.

My problem was indeed that facility of entry in oestrus, when I needed to compare with human hormonal cycling...

I will post here some images of my scanning electron observations of the rodent genital system, according to different ages and different hormonal climate.

https://www.researchgate.net/project/Side-effects-of-contraceptives-on-their-target-organs?_esc=profileProjectCards&_sg=Oe8Qg1nJ5V0v2SyODRh3vQUcijmdHQU9jOqjgreVle1FFIiGTVqdB-d5NeFrdhP5K3GOzPTL0DaAV45hVKWQbg7WM7n0DFnzcuf38wEBy-M.6vtsLCE9b1xDCL9XzCrYGLo4tV_bUY-i3Ccg65oLXnqYOznS8jSoUnSFwag48Kdb.lXbofDz3bLieodJAcvcU41HWJ02VktZqNZlPUVCSXXnBdtIR7Eo2Q8zAIpxDc7Ws&_viewIds%5B0%5D=CVdcUPJqURKFA6ZCbnbJ0MbM&_viewIds%5B1%5D=qe79XcmVsVIAwWvrrpxvOnRZ

From my observations, oestrus can arise as soon as immediately after birth time. One of the most amazing incidents we had to face, when our lab technician was cleaning the rats cages, he noticed that one of the females was in delivering procedure, and one of the male mice, noticing the cage was open,  jumped to that female cage. 22 days later, that female gave birth again... So, we believe that short contact "during/or the minute after" birth delivery, was enough for those hormonal changes to produce effect... (strange incident, indeed! - Fortunately, not reproduced in humans...-) 

Dear Masoume

I wish I can help you but it is not my field 

regards 

Saeed 

@Maria Bettencourt Pires  that is very interesting, now I can make a good discussion in my paper I really appreciate for spending time and making it clear for me.