Further it was investigated that testosterone can modulate serotonergic transmission, where serotonin plays a crucial role in depression development (Jovanovic et al., 2014). Selected animal studies analyzing the relationship between testosterone and anxiety. However, a very important study in rhesus monkeys showed that pharmacological castration reduced and testosterone supplementation normalized anxiety levels (Suarez-Jimenez et al., 2013). We were not able to reproduce the anxiolytic effects of testosterone in the elevated plus maze and in the open field (Hodosy et al., 2012). A possible mechanism can include the androgen receptor, as its blockade has been shown to prevent the testosterone-induced anxiolysis.
Additionally, physiological and also behavioral functions are exerted on a rhythmic basis. Even later, the non-genomic effects are active in parallel with the gene expression changes. While within 30 min after administration, non-genomic effects are important, later genomic effects are expected to be the major mediator. Although such research is lacking, it might be that it has some physiological role similarly to heart rhythm variability.
Within seconds, cells in the mother’s milk ducts contract, ejecting milk into the infant’s mouth. First, oxytocin is necessary for the milk ejection reflex (commonly referred to as "let-down") in breastfeeding women. Oxytocin is continually released throughout childbirth through a positive feedback mechanism. The paraventricular nuclei produce the hormone oxytocin, whereas the supraoptic nuclei produce ADH.
Nevertheless, also according to the numerous published studies and animal experiments, testosterone seems to affect brain functions. Injections, but there are indices that to study the effects of testosterone on brain functions, the steroid has to be injected directly into the target brain structure. Restoring natural circulating hormone pattern in older but also in younger animals could possibly lead also to more comprehensive results of sex hormones and behavior studies. Alternatively, aging is strongly related to decline of circulating sex hormones, disrupting thus also circadian rhythms and leading to impaired sleep or cognitive functioning (Urbanski et al., 2014). The menstrual cycle and thus the involvement of sex hormones, including testosterone, in spatial abilities was further confirmed by Pletzer et al. Such studies showed that in adult male rats administration of any dose of testosterone or the androgen receptor blocker flutamide resulted in worsening of spatial memory (Naghdi et al., 2001). In birds, evidence exists for a low testosterone period needed during the development of brain functions such as vocal memory (Korsia and Bottjer, 1991).
Selected animal studies analyzing the relationship between testosterone and spatial abilities. In Table 3, published experimental data on the effects of testosterone on spatial abilities are summarized. It has been shown that mental rotation testing affects testosterone, at least in women (Durdiakova et al., 2012). Despite all complexity, the current picture indicates that the association between testosterone and spatial abilities is curvilinear and sex-dependent. Especially, the CAG short tandem repeat in the exon 1 of the androgen receptor gene seems to be important for the action of testosterone and its metabolites (Nowak et al., 2014). When virtual Morris water maze was used, a positive correlation between testosterone and spatial navigation was found in women, but not in men (Burkitt et al., 2007). Some studies have found a positive relationship between testosterone and mental rotation in men (Silverman et al., 1999).