Mating Stimuli Influence Endogenous Variations in the Neurosteroids 3α,5α‐THP and 3α‐Diol

Progesterone facilitates and 5 α ‐dihydrotestosterone (DHT) inhibits female sexual behaviour in rodents; their metabolites, 5 α ‐pregnan‐3 α ‐ol‐20‐one (3 α ,5 α ‐THP) and 5 α ‐androstane‐3 α ‐17 β ‐Diol (3 α ‐Diol), may influence the onset and termination of lordosis. Changes in these and related steroids in hormonal states associated with differences in receptivity were investigated. Rats were assigned to oestrus, metoestrus, dioestrus, pro‐oestrus, mated, gestational days 5–7, 12–14, 18–20, or post‐partum conditions; rats 9+ months of age were considered older. Pro‐oestrus rats were exposed to the mating arena, sight and smell of a male with no tactile contact, artificial vaginocervical stimulation, standard mating, or no mating. Progesterone, 5 α ‐pregnane‐3,20‐dione, 3 α ,5 α ‐THP, oestradiol, testosterone, DHT, 3 α ‐Diol, dehydroepiandrosterone, and corticosterone were measured in plasma and whole brain, midbrain, hypothalamus, cortex, amygdala, hippocampus. 3 α ,5 α ‐THP and 3 α ‐Diol changed with reproductive state and mating stimuli. Plasma and whole brain 3 α ,5 α ‐THP and 3 α ‐Diol were significantly increased in pro‐oestrus versus dioestrus rats; plasma 3 α ,5 α ‐THP was decreased and 3 α ‐Diol increased in mated versus pro‐oestrus rats. The midbrain and hypothalamus had the most evident changes in 3 α ,5 α ‐THP and 3 α ‐Diol between dioestrus versus pro‐oestrus and pro‐oestrus versus mated rats. 3 α ,5 α ‐THP and 3 α ‐Diol were altered differently in response to mating stimuli. 3 α ,5 α ‐THP was greater in the midbrain of mated versus pro‐oestrus rats; other mating‐relevant stimuli decreased 3 α ,5 α ‐THP. Midbrain 3 α ‐Diol was increased with exposure to a male

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