Female Snake Sex Pheromone Induces Membrane Responses in Vomeronasal Sensory Neurons of Male Snakes

This paper investigated what responses female red-sided garter snake pheromone had on the Vomeronasal organ (VNO) of males. The VNO is known to play a role in detecting sex pheromones and the sex pheromone of female red-sided garter snake, composed of long chain methyl ketones, is one of the only vertebrate pheromones to be isolated and purified. In order for the VNO to be able to detect and analyze chemical signals, they must be dissolved in the aqueous medium of the VNO. However, the female garter snake sex pheromone is nonpolar and thus insoluble in water. This experiment not only investigated the mechanism of the response of the male VNO sensory neurons, it also investigated how the VNO is able to detect the insoluble chemical.

After collecting 36 males and 4 females from Manitoba, Canada at the start of mating season, the snakes were taken to Brooklyn, NY where the females were used to extract the sex pheromone and the males were killed for their Vomeronasal organs. Because the Harderian gland homogenate is the major component of the VNO fluid, the authors attempted to dissolve the sex pheromone into it. They were successful and it was determined that this fluid is used by the snake to allow the pheromone to be detected by the VNO. After dissolving the pheromone into the Harderian gland homogenate, the solution was applied to slices of the male VNO. It was found that there was an inward flow of electrons indicating a positive response. The female sex pheromone solution was also applied to samples of the female VNO, but there was no response, indicating sexual dimorphism in the VNO response.

This paper mentions several topics discussed in class. First, unlike many mate attraction pheromones, the female garter snake pheromone is high-molecular weight, which indicates low dispersal and high persistence. The sex pheromone is expressed on the dorsal surface of females which means that it is likely produced by exocrine secretory glands. Another point discussed in class and emphasized by this paper is that chemicals must be dissolved in liquid in order to be detected and analyzed by the Vomeronasal organ.

G.Z. Huang, J.J. Zhang, D. Wang, R.T. Mason and M. Halpern. (2006) Female snake sex pheromone induces membrane responses in vomeronasal sensory neurons of male snakes. Chem. Senses. 31, pp. 521–529.