Fig. 1.

Experimental scheme of olfactory or mating stimulation. Intact male rats were divided into three groups: exposure to clean bedding, exposure to female-soiled bedding, and placed with a female for mating with female-soiled bedding. The males were kept in their home cages and then introduced to each testing cage containing fresh bedding or female-soiled bedding without/with an ovariectomized (OVX) + estradiol-17β (E₂) female rat. The fresh bedding or the female-soiled bedding taken from the cage, where an OVX + E₂ female rat had been kept for a week, was placed into a testing cage without/with an OVX + E₂ rat 30 min before introducing a male rat into the testing cage (A). Male rats were subjected to the blood sampling in their home cage (for the first 24 min) and then in the testing cage (for the last 60 min) at 6 min intervals, and the plasma samples were used for luteinizing hormone (LH) and testosterone assays (B). Five minutes after the onset of the exposure to each stimulus in the testing cage, the male brain samples were taken for histological analysis for Kiss1 mRNA expression (C).