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Role of the brain and accessory olfactory system in the block to pregnancy in mice
Abstract:
Selective lesions have been made to the receptors in the main and accessory olfactory systems. In the absence of the accessory receptors, female mice are not able to show a neuroendocrine response to male pheromones but are able to detect male odours which induce the response. In the absence of main olfactory receptors, such discrimination of male odours is not possible, but the neuroendocrine response resulting in a block to pregnancy is maintained. These experiments suggest that cognitive aspects of olfaction are not essential for pregnancy block to occur and that in mice the dual olfactory systems are functional as well as anatomically distinct. Moreover, strain recognition can occur at the level of the accessory olfactory system without the female being able to display a behavioural awareness of this 'recognition'.
Insights
Female mice require accessory olfactory receptors for pheromone-induced neuroendocrine responses. However, pregnancy block can occur without main olfactory receptors, indicating distinct roles for these sensory systems.
Area of Science:
- Neurobiology
- Olfactory System Research
- Animal Behavior
Background:
- The mammalian olfactory system comprises main (MOS) and accessory (AOS) olfactory systems.
- These systems are anatomically distinct and process different olfactory information.
- The AOS is primarily involved in processing pheromones, crucial for social and reproductive behaviors.
Purpose of the Study:
- To investigate the distinct roles of the main and accessory olfactory systems in female mice.
- To determine the necessity of each olfactory system for pheromone detection and neuroendocrine responses.
- To elucidate the contribution of olfactory systems to the Bruce effect (pregnancy block).
Main Methods:
- Selective lesioning of olfactory receptors in the main and accessory olfactory systems of female mice.
- Assessment of neuroendocrine responses to male pheromones.
- Evaluation of the ability to detect male odors and discriminate between them.
- Observation of pregnancy block (Bruce effect) following mating with a male of a different strain.
Main Results:
- Absence of accessory olfactory receptors impaired neuroendocrine response to male pheromones but not odor detection.
- Absence of main olfactory receptors prevented odor discrimination but preserved the pregnancy block.
- Strain recognition occurred at the accessory olfactory system level, independent of behavioral awareness.
Conclusions:
- The main and accessory olfactory systems are functionally and anatomically distinct in mice.
- Cognitive aspects of olfaction are not essential for the pregnancy block.
- The accessory olfactory system mediates pheromone detection and strain recognition, crucial for reproductive neuroendocrine regulation.