The expression of androstenone receptor (OR7D4) in vomeronasal organ and olfactory epithelium of horses.

The study investigates the presence and expression of the odorant receptor, OR7D4, in the vomeronasal and olfactory regions of horses, showing that horses can perceive the steroidal pheromone androstenone.

Study Objective and Methodology

The primary aim of the study was to inspect the presence and expression of the odorant receptor OR7D4 in two regions, the vomeronasal organ (VNO) and olfactory epithelium (OE), in horses. This receptor responds to androstenone, a mammalian steroidal pheromone used in animal communication. Previous studies highlighted changes in the behaviors of boars and dogs after being sprayed with androstenone, but there’s been no report on OR7D4 expression in the VNO and OE in other mammals apart from humans.

• The researchers collected tissue samples from the VNO and nasal cavity of six thoroughbred horses.
• Using reverse transcription-polymerase chain reaction, they investigated the existence of the OR7D4 gene.
• The expression of OR7D4 in the respective regions was determined through Western blot and immunofluorescence techniques.

Results

Following the examination, the researchers determined that:

• The bands indicative of OR7D4 were identified at approximately 462 base pairs (bp).
• Using Western blot, the protein band related to OR7D4 in the VNO and OE was detected at 38 kilodaltons (kDa).
• In immunofluorescence tests, the cilia (hairlike structures) and cytoplasm (cell’s internal component) of the olfactory receptor cells in the VNO and nasal cavity tissues exhibited immunolabeling with OR7D4 antibody.
• The intensity level of OR7D4 protein bands in a part of the ethmoidal concha tissues (bony projections inside the nasal cavity) was not significantly different between female (mares) and castrated male (geldings) horses.

Conclusion

The research concluded that thoroughbred horses are capable of perceiving androstenone via expression of the OR7D4 in the vomeronasal and olfactory regions. This finding contributes to the broader understanding of mammalian chemical communication through pheromones.