For years, the biochemical processes that are triggered by harmful and non-harmful stimuli at the central nervous system level have been extensively studied by the scientific community through numerous techniques and animal models. For example, one of these techniques is the use of immediate expression genes, which is a useful, accessible, and reliable method for observing and quantifying cell activation. It has been shown that both the c-fos gene and its protein c-Fos have rapid activation after stimulus, with the length of time that they remain active depending on the type of stimulus and the activation time depending on the stimulus and the structure studied. Fos requires the participation of other genes (such as c-jun) for its expression (during hetero-dimer forming). c-Fos dimerizes with c-Jun protein to form factor AP-1, which promotes the transcription of various genes. The production and removal of c-Fos is part of cellular homeostasis, but its overexpression results in increased cell proliferation. Although Fos has been used as a marker of cellular activity since the 1990s, which molecular mechanism participates in the regulation of the expression of this protein is still unknown because the gene and the protein are not specific to neurons or glial cells. For these reasons, this work has the objective of gathering information about this protein and its use in neuroscience.

In all species, sexual behavior is directed by a complex interplay between steroid hormone actions in the brain that give rise to sexual arousability and experience with sexual reward that gives rise to expectations of competent sexual activity, including sexual arousal, desire, and performance. Sexual experience allows animals to form instrumental and Pavlovian associations that predict sexual outcome and thereby directs the strength of sexual responding. Although the study of animal sexual behavior by neuroendocrinologists has traditionally been concerned with mechanisms of copulatory responding, more recent use of conditioning and preference paradigms, and a focus on environmental circumstances and experience, has revealed behaviors and processes that resemble human sexual responses. In this paper, we review behavioral paradigms used with rodents and other species that are analogous or homologous to human sexual arousal, desire, reward, and inhibition. The extent to which these behavioral paradigms offer predictive validity and practicality as preclinical tools and models is discussed. Identification of common neurochemical and neuroanatomical substrates of sexual responding between animals and humans suggests that the evolution of sexual behavior has been highly conserved and indicates that animal models of human sexual response can be used successfully as preclinical tools.

Paced copulation induces conditioned place preference in female rats. The authors examined whether associating almond-scented males with paced copulation induces conditioned partner preference. The paired group received 4 paced copulations with almond-scented males and 4 nonpaced copulations with unscented males sequentially at 4-day intervals. The unpaired group received the opposite order of association, whereas the randomly paired group received random associations. A 4th group received a single pairing. On the final test, females were placed into an open field with 2 males, 1 scented and 1 unscented. Females in the paired group solicited the scented male more frequently, and most chose the scented male for their 1st ejaculation. Thus, an odor paired with paced copulation elicits conditioned partner preference in female rats.