The Role of Oxytocin Release in the Mediobasal Hypothalamus of the Sheep in Relation to Female Sexual Receptivity

Abstract

In vivo microdialysis and retrodialysis were used to investigate the role of oxytocin (OXY) release in the mediobasal hypothalamus (MBH) of the ewe in the control of sexual receptivity. Initial experiments showed that OXY release was significantly increased in ovariectomized animals treated with progesterone and oestradiol when they were sexually receptive towards males and received intromissions. No such increases were seen during tests where the ewes were receptive but the males were prevented from achieving intromission. By contrast, OXY release was significantly reduced in tests where the ewes were not receptive to the male. In a second experiment artificial vaginocervical stimulation (VCS) was found to significantly increase OXY release when the animals were treated with oestradiol and this effect was potentiated by progesterone priming. OXY release in the MBH was not significantly altered by VCS in the presence of progesterone priming alone. Plasma OXY concentrations were significantly increased by VCS following all three hormone treatments but no one treatment was significantly more effective than another. Noradrenaline release in the MBH was only significantly increased following VCS when progesterone priming was given before oestradiol treatment. No effects of VCS on release of GABA, glutamate or dopamine were seen but their basal concentrations were significantly increased by the combined steroid treatment compared to oestradiol alone. In a third experiment it was found that OXY (10 microM) infused bilaterally into the MBH of receptive ewes, by retrodialysis, significantly decreased sexual receptivity and increased the release of noradrenaline and GABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular approaches to aggregation behavior and social attachment

“…The main source of intracerebral OT in both rats and sheep are parvocellular cells in the paraventricular nucleus (PVN) of the hypothalamus (Sofroniew, 1983;Broad et al, 1993;Crowley et al, 1995). These cells send oxytocinergic processes to many different brain areas, including the MPOA, the olfactory bulb, the bed nucleus of the stria terminalis, the amygdala, the ventral tegmental area, and the mediobasal hypothalamus (Fig.…”

A framework for the present and future development of experimental models of female sexual dysfunction

“…CNS lesioning, microdialysis and microinjection studies combined with behavioral methods have provided important insight into the neurochemical pathways involved in the sexual response. 15,16,[19][20][21][22] Several measurements of sexual behaviors have been described including lordosis, hop, dart and kick responses, escapes from grasp, aggressive posture, fight attack, front attack, defensive/submissive posturing, rough grooming. These behaviors represent both procopulatory and anticopulatory responses 23 and the ratio between the two types has been used as an indicator of sexual interest.…”

Is Luteinizing Hormone Secretion Modulated by Endogenous Oxytocin in the Mare? Studies on the Role of Oxytocin and Factors Affecting Its Secretion in Estrous Mares1

“…Infusion of OT into the ventromedial nucleus (VMN) of the hypothalamus stimulates sexual receptivity in female rats [Arletti & Bertolini, 1985], but not in ewes [Kendrick et al, 1993]. In female goats, plasma OT rises accompany displays of estrus [McNeilly & Ducker, 1972].…”

“…Plasma OT increases after copulation in sows' [Claus & Schams, 1990] or after masturbation to orgasm in women [Carmichael et al, 1987]. Vaginocervical stimulation elevates plasma OT in sexually receptive ewes [Kendrick et al, 1993] and cows [Schams et al, 1982] and enhances OT release within the VMN in ewes [Kendrick et al, 1993]. Copulation is less effective than vaginocervical stimulation in raising OT in the VMN in ewes [Kendrick et al, 1993] and may not alter plasma OT in cows [Schams et al, 1982] or ewes .…”

“…Vaginocervical stimulation elevates plasma OT in sexually receptive ewes [Kendrick et al, 1993] and cows [Schams et al, 1982] and enhances OT release within the VMN in ewes [Kendrick et al, 1993]. Copulation is less effective than vaginocervical stimulation in raising OT in the VMN in ewes [Kendrick et al, 1993] and may not alter plasma OT in cows [Schams et al, 1982] or ewes . It has been suggested that postcopulatory OT increases may serve to facilitate gamete transport [Wathes, 1984;Carmichael et al, 1987], since OT stimulates the motility of the female reproductive tract, especially when estrogen levels are high [Wathes, 1984].…”