Humoral pathway for transfer of the boar pheromone, androstenol, from the nasal mucosa to the brain and hypophysis of gilts

Signaling and priming pheromones play an important role in intraspecies beh avioral and sexual interactions and in the control of reproduction. It is g enerally accepted that pheromones act by stimulating the dendritic receptor s in the mucus-imbedded cilia of olfactory neurons massed in the olfactory epithelium. The boar pheromone androstenol, known to induce sexual behavior in pigs, is 1 of 2 pheromones that have been chemically defined, tritiated and thus made available for use in studies. In Experiment 1, sexually matu re cyclic gilts at Days 16 to 21 of the estrous cycle were humanely killed and the heads separated from the bodies. The heads were attached to a perfu sion system using heated, oxygenated, heparinized, autologous blood. A tota l amount of 10(8) dpm (758 ng) of H-3-5 alpha-androstenol ((3)HA) was eithe r infused into the angularis oculi veins that drain the nasal cavities (n=7 ) over a 5-min period or applied through intranasal catheters onto the muco se surface (n=16) for 2 min. In both groups frequent blood samples were col lected from the carotid rete and from venous effluent. Concentration of (3) HA in the arterial blood of the carotid rete after direct (into angularis o culi veins) or indirect (onto the nasal mucosa) administration of (3)HA int o veins draining the nasal cavities was significantly higher than backgroun d radioactivity before (3)HA administration (P<0.0001 and P<0.05, respectiv ely). The (3)HA was selectively accumulated (compared with the respective c ontrol tissue) in the neurohypophysis (P<0.001), adenohypophysis (P<0.01), ventromedial hypothalamus (P<0.05), corpus mammillare (P<0.01), and perihyp ophyseal vascular complex (P<0.001). In a second in vitro experiment, activ e uptake of (3)HA into the nasal mucosa of the proximal, respiratory segmen t of the nasal cavity was observed. These results demonstrate a humoral pat hway for the transfer of pheromones from the nasal cavity to the hypophysis and brain. Androstenol was taken up by the respiratory part of the nasal m ucosa, resorbed into blood, transported to the cavernous sinus and transfer red into the arterial blood of the carotid rete (supplying the hypophysis a nd brain), and then selectively accumulated in the hypophysis and certain b rain structures. (C) 1999 by Elsevier Science Inc.