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

Androstenone is the first mammalian steroidal pheromone to be identified. Pheromones are chemicals that animals use to communicate within a species. Pheromone detections are related to vomeronasal organ (VNO) and olfactory epithelium (OE) in mammals. Olfactory Receptor Family 7 Subfamily D Member 4 (OR7D4) is an odorant receptor that responds to androstenone. Several studies indicated that spray with androstenone changes behaviors of the boar and dogs. However, the expression of OR7D4 in VNO and OE was not reported in mammals except human. Thus, the main objectives of this study were to investigate the expression of OR7D4 in VNO and OE of horses. Tissue samples were collected from the VNO and nasal cavity of 6 thoroughbred horses. The presence of OR7D4 gene was investigated with reverse transcription-polymerase chain reaction. The expression of OR7D4 was determined using Western blot and immunofluorescence. As a result, the bands for OR7D4 were observed at approximately 462 bp. The protein band of OR7D4 of VNO and OE was detected at 38 kDa. Immunofluorescence result showed that the cilia and cytoplasm of olfactory receptor cells of VNO and nasal cavity tissues were immunolabeled with OR7D4 antibody. The intensity of OR7D4 protein bands in the ventral region of the ethmoidal concha tissues was not significantly different between mares and geldings. In conclusion, thoroughbred horses are capable of androstenone perception through OR7D4 expressed in the VNO and OE. (c) 2020 Elsevier Inc. All rights reserved.

Automated summary

This study aimed to investigate the expression of OR7D4 in the VNO and OE of horses, with experiments detecting the presence of the OR7D4 gene in the equine VNO. Analysis through Western blot and immunofluorescence showed that horses are capable of perceiving androstenone through OR7D4 expressed in the VNO and OE.