Of mice and rats: Key species variations in the sexual differentiation of brain and behavior

Abstract

Mice and rats are important mammalian models in biomedical research. In contrast to other biomedical fields, work on sexual differentiation of brain and behavior has traditionally utilized comparative animal models. As mice are gaining in popularity, it is essential to acknowledge the differences between these two rodents. Here we review neural and behavioral sexual dimorphisms in rats and mice, which highlight species differences and experimental gaps in the literature, that are needed for direct species comparisons. Moving forward, investigators must answer fundamental questions about their chosen organism, and attend to both species and strain differences as they select the optimal animal models for their research questions.

Does the early social environment affect structure and consistency of personality in wild‐type male rats?

“…Nevertheless, this presence or absence of one female in a litter may account for the difference between our study and the earlier ones. The different species used might have contributed as well, although the two rodents species are very similar with in regard to ontogeny, physiology, and behavior differences in behavior (Bonthuis et al, 2010). Also, animals were usually tested at a younger age (from 50 to 90 pnd) in comparison to our data and a possible interaction between age and development of aggression might have occurred that may explain the different trend of aggressive behavior in our data (Tab.…”

Who, What, Where, When (and Maybe Even Why)? How the Experience of Sexual Reward Connects Sexual Desire, Preference, and Performance

“…This occurs in two phases in mammals: (1) an ''organizational'' phase in which the male phenotype differentiates from the female''default''through the combined action of androgens and estrogens during a critical perinatal period that ''sculpt''a male brain; and (2) during a subsequent''activational'' phase in which gonadal steroid secretion acts on those differentiated brain regions to activate the neuroendocrine systems necessary for reproduction and the behaviors that will bring it about (Bonthuis et al, 2010;Lenz & McCarthy, 2010;Nelson, 2005). Thus, the brains of male mammals are differentiated from the female default by early hormone actions, which lead to different patterns of sexual responding in adulthood driven by two distinct steroid hormone secretion patterns, one continuous (male) and one cyclic (female).…”

Testosterone and Its Effects on Human Male Adolescent Mood and Behavior: A Systematic Review

“…This includes the activational and organizational effects of testosterone on neural circuitry and neurohormones [8], the effects of androgenic anabolic steroids [8], and the influence of prenatal testosterone on behavior [9,10]. Although these models can inform human studies, we know that variation between strains and species is significant [11] and may or may not translate to the complexities of human behavior.…”