Estrogens, androgens and generalized behavioral arousal in gonadectomized female and male C57BL/6 mice

Abstract

General arousal has been operationally defined as enhanced motor activity and enhanced intensity of response to sensory stimuli. Even though the effects of gonadal hormones on mating behavior have been much studied, their potential effect on generalized arousal, as defined above, has never been evaluated. In the present study we employed a thoroughly validated assay of general arousal to determine the effects of estradiol (E) and testosterone (T) in gonadectomized female and male mice, respectively. The steroids were administered in three different ways: A fast-acting, water soluble preparation given intraperitoneally, an oil solution given subcutaneously, and an oil solution in a subcutaneous Silastic capsule. Motor activity and responses to sensory stimuli were recorded for 24 h, 91 h, and seven days following hormone administration, respectively. All measures of arousal varied according to the day/night cycle. The water soluble steroid preparation had no reliable effect. When the same doses of estradiol and testosterone were administered subcutaneously in an oil vehicle no effect of either treatment on arousal was observed. The subcutaneously implanted capsule containing estradiol or testosterone had a delayed effect on motor activity in females (four to seven days) but no effect in males. The long time required by the gonadal hormones for affecting arousal would be consistent with, but does not prove, a genomic action. The limited effects of E and T in our arousal assay suggest to us that the strongest actions of these hormones on arousal occur in the context of sequences of responses to sexually relevant stimuli.

The behavioral and physiological effects of high‐fat diet and alcohol consumption: Sex differences in C57BL6/J mice

“…Even without any of the experimental treatments, home‐cage locomotor activity, as opposed to open field exploratory locomotor behavior, was much greater in female mice than male mice. Of particular note, another study has shown that this difference in activity still can persist even if female rodents are ovariectomized (Chu, Gagnidze, Pfaff, & Ågmo, ). Although removal of the ovaries does not affect locomotor activity, centrally located (i.e., brain) estrogens and estrogen receptors (ER) may still be implicated in why female mice exhibit more movement than males.…”

Androgen-primed castrate males are sufficient for methamphetamine-facilitated increases in proceptive behavior in female rats

“…Pfaff and colleagues have demonstrated a role of gonadal steroids in arousal that suggests steroids, while having modest effects on generalized arousal, have a greater effect on reproductive behaviors/sexual arousal, a component of a general arousal (Chu et al, 2015). In our current model of MA-induced enhancement of proceptive behaviors, MA may prime a specific neural network involved in female sexual behaviors resulting in enhanced activation when EB and P are present.…”

The Role of Ovarian Hormones and the Medial Amygdala in Sexual Motivation

“…Both excitatory and inhibitory neurobiological factors influence sexual motivation (reviewed in 10, 30); however, this report will focus on the neurobiological factors that increase motivation for sexual behaviors. One such influence on sexual motivation is non-specific or generalized arousal, which sets the general level of activity in the brain and can influence specific sexual motivations (14, 31). Indeed, this process may explain how sexual arousal increases subjective sexual desire.…”

“…Several classic studies have demonstrated the role of both estradiol and progesterone in triggering both proceptive and receptive sexual behaviors in the rat (87). These hormones strongly affect the responses to sexually relevant stimuli, with modest effects on generalized arousal (31). The neural circuitry for lordosis, particularly the role of the ventrolateral portion of the ventromedial hypothalamus (vlVMN), has been well established (88, 89); however, the neural circuitry underlying sexual motivation in the female has not been as well elucidated.…”

“…Steroid hormones play a role in this central state, as reflected in the increases sexual motivation during the periovulatory period (31, 33). Moreover, these hormones also increase the incentive properties of sexual stimuli with high levels of estradiol increasing emotional valence to erotic imagery and interest in subsequent images (76).…”