London, July 21 : Researchers from the European Molecular Biology Laboratory (EMBL) in Monterotondo, Italy have revealed that pregnant mice have a unique way of protecting their unborn.
The team found that chemical changes in brain help the pregnant mouse ignore the smell of strange male's urine that can cause a miscarriage and re-start the ovulatory cycle.
A series of the chemical signal dopamine in the main olfactory bulb, one of the key brain areas for olfactory perception, blocks male odours.
The researchers revealed that exposure to an alien male's urine averts implantation of embryos into the uterus of pregnant mice and brings her back into ovulatory cycle.
The odour stalls the release of the pregnancy hormone prolactin and creates mating opportunity for the strange male. It is also beneficial for the female because it avoids infanticide by the strange male after birth.
However, after 3 days into pregnancy the urine odour has no impact on pregnancy as embryos have already been implanted into the uterus. "At day 3 of the pregnancy a chemical change occurs in the brain of the expectant mother that makes her unable to perceive male odours. This seems to mark a point of no return for the pregnancy," Nature Neuroscience quoted Liliana Minichiello, at the EMBL Mouse Biology Unit as saying.
The surge of chemical signal dopamine, activated by physical stimulation during mating weakens the perception and discrimination of social odours contained in male urine.
The researchers found that treating the expectant mice with chemicals that obstructs the dopamine receptor D2 eliminated the barrier effect and brought back the odour sensing and favoured pregnancy disruption.
The study appears in the current issue of Nature Neuroscience.