Estrogens oxytocin

Serotonin also affects the emotions of love and romance. Androgens, estrogens, oxytocin, and vasopressin increase the sex drive, whereas increased levels of synaptic serotonin, such as result from the taking of reuptake transporter inhibitors, suppress the sex drive and inhibit feelings of attraction by the opposite sex. Dopamine and norepinephrine increase the sex drive. 

Progesterone produces direct membrane effects [16]. These include actions that promote maturation of spermatozoa as well as oocytes and facilitation of the release of neurotransmitters such as dopamine and LH-releasing hormone (LHRH) (Fig. 52-7). Membrane actions of progesterone also activate oxytocin receptors in the hypothalamus in a way that enables oxytocin to turn on sexual behavior in the estrogen-primed female rat [3],... 

In order to review these putative relationships it is first useful to define a subset of well-characterized hormones and neurotransmitters that have been implicated in behavior. The chemicals selected for discussion here are among those for which a robust relationship with behavior has been proposed, including steroids (estrogens, progestins, androgens and glucocorticoids), proteins (prolactin) and the neuropeptides (oxytocin and vasopressin). All of these chemicals may act as hormones, neurotransmitters and/or neuromodulators. In addition, to understand the action of these hormones, it is helpful to be familiar with some of the more common neurotransmitters (described below). Space does not permit a discussion of the behavioral effects of many additional compounds with endocrine or paracrine properties. 

Donna Toufexis completed her doctoral training in neuroendocrinology at McGill University in Montreal, Canada, and postdoctoral training at Concordia University in Montreal. Toufexis is presently a research associate at the Center for Behavioral Neuroscience (CBN) at Emory University in Atlanta. Her primary research interest is the characterization of brain mechanisms that govern fear and anxiety. In particular, Toufexis is interested in the role that neuroactive hormones estrogen, testosterone, and oxytocin play in the regulation of fear and anxiety. 

An emerging group of antidepressant interventions comprises several hormones that have been shown to have mood-elevating or mood-modulating effects (see Halbreich, Chapter 17, in this volume). This group includes mostly cortisol suppressors, thyroid hormones, estrogen, and other steroids. However, more recently several other hormones, such as melatonin and oxytocin, were proclaimed as players in the field, but their place is still to be claimed. 

Gonadal hormones Estrogens Progestins Androgens Neurosteroids Thyroid hormones Melatonin Vasopressin Oxytocin... 

Regulation at the genetic level is often observed for hormones that can regulate the rate of synthesis either of their own receptor or of other functionally related receptors (e.g., regulation of oxytocin receptor synthesis in the utems by estrogens). 

Estrogens influence the breast tissue at puberty, during each ovulatory cycle, and during pregnancy they participate in duct formation, and, in conjugation with progesterone, oxytocin, and other hormones, prepare the breasts for lactation. 

The primary stimulus for oxytocin release is suclding. Stimulation of tactile receptors located around the nipples of the breasts initiates an action potential that propagates along afferent nerve fibers through the spinal cord and mid-bram to the hypothalamus. The cell bodies in the paraventricular nucleus are then stimulated, resulting in the episodic release of oxytocin. Stretch receptors in the uterus and possibly in the vaginal mucosa may also initiate action potentials in afferent nerve fibers that ultimately stimulate the release of oxytocin from the neurohypophysis. Estrogens enhance the response of oxytocin to these stimuli. The influence of other parts of the brain on the release of oxytocin has been reported emotional stress, for instance, inhibits lactation. 

Myometrium Estrogen decreases the resting membrane potential of the myometrium and increases ciliary activity of the endometrial epithelium. Rising levels of estradiol prior to ovulation cause the smooth muscle of the fallopian tubes to become increasingly contractile at about the time of ovulation. This and the increased activity of cilia on the endometrial lining facilitate entry of the oocyte-cumulus complex into the lumen of the fallopian tube at the time of ovulation. In the pregnant uterus shortly before parturition, estradiol stimulates the formation of gap junctions and the production of myometrial receptors for oxytocin, PGF, and PGE, and thereby promotes the myometrial contractions that facilitate parturition. 

Choleris E, Ogawa S, Kavaliers M, Gustafsson JA, Korach KS, MugUa LJ, Pfaff DW (2006) Involvement of estrogen receptor alpha, beta and oxytocin in sodal discrimination A detailed behavioral analysis with knockout female mice. Genes Brain Behav 5 528-539. 

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