Neuron- and microglia-specific immunoexpression in steroid-independent male sexual behaviour in castrated B6D2F1 male mice

Sexual behaviour is necessary for procreation for several species and is traditionally viewed to be regulated by sex steroid hormones. However, several species exhibit steroid-independent sexual behaviour, and its molecular understanding is only beginning to be uncovered. The main goal of our experiment was to provide new insight into cell-specific roles that both neuronal and non-neuronal cells may play in steroid-independent male sexual behaviour. Forty B6D2F1 hybrid male mice underwent orchidectomy and were tested for reinstatement of steroid-independent male sexual behaviour after an extended period of social isolation caused by the COVID-19-mandated laboratory shutdown. After 62 weeks post-orchidectomy, 20.59% demonstrated reinstatement of steroid-independent male sexual behaviour (identified as ‘steroid-independent persistent maters’), while 23.53% of the males did not display steroid-independent male sexual behaviour (identified as ‘steroid-independent non-maters’). Using flow cytometry, we compared the preoptic area immunoexpression in NeuN+ neurons and Iba1+ microglia between steroid-independent persistent maters and steroid-independent non-maters (N = 5-6 per group). We found neuronal immunoexpression up-regulated for amyloid precursor protein and androgen receptor, as well as down-regulated for glucocorticoid receptor in steroid-independent persistent maters compared to steroid-independent non-maters. In conjunction, microglial immunoexpression of amyloid precursor protein was up-regulated in steroid-independent persistent maters compared to steroid-independent non-maters. These data suggest there are cell-specific immunoexpression differences, including the role of non-neuronal cells in steroid-independent male sexual behaviour.