Neural Basis of Responses to Sex Pheromones

The ability of insects to detect and discriminate between a variety of pheromones with great sensitivity depends on the presence of specific neural structures in the neuropile of the male antennal lobes. The female antennal lobe lacks these structures. The electrophysiological signals resulting from interaction between pheromonal molecules and antennal olfactory receptors are passed via the olfactory nerve to the specific part of the brain containing specific neural circuitary to decode complex pheromonal signals.

The brain then translates pheromonal information into the act of directional locomotion or orientational responses. There are pheromones that act more slowly and have longer lasting effects. For example, if a newly fertilised female mouse is caged with a strange male, the odor of that male will terminate pregnancy. The pheromone responsible comes from the urine of the male. It is received by the olfactory receptors of the female and triggers activity in the hypothalamus which directs the pituitary to release a hormone that reduces the steroid hormone output of the ovaries. The uterus does not receive adequate hormones for implantation of foetus and the pregnancy aborts.