Estrous Cyclicity in Mammals

Feder, Harvey H.

doi:10.1007/978-1-4684-3881-9_10

Cited by 32 publications

(42 citation statements)

References 385 publications

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“…The oestrus cycle was monitored for 2 weeks prior to the experiments to ensure that all subjects were cycling normally. The stage of the oestrus cycle was determined using a lavage technique and was based on the description provided by Feder (1981). All of the rats demonstrated a consistent 4±5 day oestrous cycle.…”

Section: Oestrus Cycle Determinationmentioning

confidence: 99%

Cyclical changes in endogenous levels of oestrogen modulate the induction of LTD and LTP in the hippocampal CA1 region

Good

Day

Muir

1999

Eur J of Neuroscience

135

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The present study investigated the effects of naturally fluctuating endogenous levels of oestrogen on the induction and maintenance of long-term potentiation (LTP) and long-term depression (LTD) in the CA1 region of the hippocampus. Using an anaesthetized in vivo preparation, the results showed that the induction of LTP was augmented during the pro-oestrous stage of the oestrous cycle. In contrast to LTP, however, the induction of paired-pulse LTD was severely attenuated during pro-oestrous, but was clearly manifested by rats during met/dioestrous and oestrous stages of the cycle. These findings are discussed with reference to: (i) the modulatory effects of oestrogen on N-methyl-D-aspartate (NMDA) receptor function and gamma-aminobutyric acid (GABA) neurotransmission in the hippocampus; and (ii) the functional implications that such cyclical changes in synaptic plasticity have for learning and memory processes supported by the hippocampus.

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Section: Oestrus Cycle Determinationmentioning

confidence: 99%

Cyclical changes in endogenous levels of oestrogen modulate the induction of LTD and LTP in the hippocampal CA1 region

Good

Day

Muir

1999

Eur J of Neuroscience

135

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“…Female rodents typically used in laboratory behavioural research have high plasma concentrations of oestrogens at the time of behavioural oestrus. After ovariectomy (OVX) replacement of physiological amounts of oestrogens (in some species progesterone is needed as well) are able to reinstate sexual behaviour (24)(25)(26). Thus, there is no reason to postulate the involvement of neural aromatization of T to E, in the normal expression of sexual behaviour in these species.…”

mentioning

confidence: 99%

Evidence that Neural Aromatization of Androgen Regulates the Expression of Sexual Behaviour in Female Musk Shrews

Rissman

1991

J Neuroendocrinology

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The experiments reported on here were conducted to test the hypothesis that sexual behaviour in the female musk shrew (Suncus murinus) is regulated by the neural aromatization of testosterone to oestradiol. In the first experiment ovariectomized animals received subcutaneous hormone implants containing either an aromatizable androgen (testosterone or androstenedione), a nonaromatizable androgen (dihydrotestosterone or methyltrienolone), or cholesterol. Only females that received an aromatizable androgen exhibited significant amounts of sexual behaviour as compared with controls (cholesterol). To examine the role of the oestrogen receptor, the anti-oestrogen, tamoxifen (200 or 400 pg daily) was given to ovary intact or ovariectomized females treated with testosterone. Tamoxifen treatment had significant negative effects both on female sexual behaviour and on the weights of several peripheral tissues as compared with control treatments. A similar set of experiments was conducted to examine the effect of an anti-androgen on female sexual behaviour. The androgen receptor blocker, flutamide, had no effect on sexual behaviour or weights of peripheral tissues. To determine whether flutamide can act as an anti-androgen in this species two final experiments were conducted in male musk shrews. Flutamide treatment in males did affect several measures of sexual behaviour. In summary, these data demonstrate that the oestrogen receptor is involved in the control of female copulatory behaviour. The androgen receptor plays a role in the expression of male, but not female, sexual behaviour. Female musk shrews display copulatory behaviour in advance of follicular development when oestradiol concentrations in plasma are very low. Thus, they may have evolved a strategy of aromatizing peripherally produced androgens in the brain to concentrate the oestrogen required for the expression of sexual behaviour.The steroid hormone testosterone (T) can enter its many target tissues via one of two avenues. T can either bind to androgen receptors directly or after it has been reduced to one of its androgenic metabolites. Alternatively, T may be aromatized in the cytoplasm to oestradiol (E2) and the nucleus can be accessed via binding to oestrogen receptors (1 -3). Somewhat paradoxically, peripherally produced T appears to require neural aromatization (and subsequent binding to oestrogen receptors) in order to promote copulatory behaviour in a number of male animalsThe largest data sets that test the aromatization hypothesis have been generated in male rats and quail. The evidence supporting the hypothesis is that first, after castration and hormone replacement, either T or pharmacological doses of E, are able to reinstate male sexual behaviour (13,15,22,23). Second, only androgens that can be aromatized to oestrogens are behaviourally effective after castration (6,13,15,16,22). In addition, drugs that inhibit aromatization block male sexual behaviour ( 5 , 7, 16) and when anti-hormones are administered along with T replacement the blo...

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“…In the presence of a sexually active male rat, the complete expression of female mating behavior includes receptive (lordosis) and proceptive (darting, hopping, ear wiggling) responses. The sequential presence of E2 followed by Pis essential in that P facilitation ofestrous behavior requires prior exposure to E2 (3).…”

mentioning

confidence: 99%

Hormonal Activation of Female Sexual Behavior is Accompanied by Hypothalamic Norepinephrine Release

Vathy

Etgen

1989

J Neuroendocrinology

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The present study employed the intracranial microdialysis technique to measure norepinephrine release in the ventrolateral dendritic fields of the ventromedial hypothalamus of freely-moving animals before and during ovarian steroid (estradiol and progesterone) activation of female sexual behavior (lordosis). One day after implantation of a dialysis probe, animals were injected with 3 ,ug of estradiol benzoate followed 44 h later by 200 pg of progesterone. introduction of a male rat 4 h after progesterone treatment was correlated with dramatic increases in extracellular norepinephrine levels measured in dialysates of the ventrolateral ventromedial hypothalamus of female rats which displayed high levels of lordosis behavior. In contrast, female rats given the same steroid treatment but which did not show lordosis responses did not have elevated norepinephrine levels in their dialysates. Moreover, animals that received an estrogen antagonist concurrently with the estrogen treatment had neither an increase in ventromedial hypothalamic levels of norepinephrine during behavior testing nor did they display lordosis. These results indicate a close relationship among ovarian steroids, noradrenergic transmission in the ventromedial hypothalamus, and the expression of female sexual behavior.Lordosis is a component of female sexual behavior in rodents which is regulated by the ovarian steroids estradiol (E2) and progesterone (p) and is displayed in response to specific somatosensory stimuli (1,2). In the presence of a sexually active male rat, the complete expression of female mating behavior includes receptive (lordosis) and proceptive (darting, hopping, ear wiggling) responses. The sequential presence of E2 followed by Pis essential in that P facilitation ofestrous behavior requires prior exposure to E2 (3).It is believed that E2 and P exert their facilitatory effects on lordosis by acting on target neurons in the ventromedial nucleus of the hypothalamus (VMN) (4). The ventrolateral dendriticfields of these neurons are densely innervated by norepinephrine (NE) neurons originating in the brainstem (5, 6). Moreover, lesions which eliminate the NE input to the hypothalamus also abolish hormone-facilitated lordosis behavior in female rats (7,8). Thus, we have hypothesized that E2 and P regulation of female mating behavior may be mediated in part by augmentation of NE transmission in the ventromedial hypothalamus (VMH). This hypothesis was supported by our previous study employing intracranial microdialysis of the ventrolateral VMH in urethaneanesthetized female rats (9). We demonstrated that combined treatment with E2 and P. but neither E2 nor P alone, enhances KCI-evoked N E release in the ventrolateral VMH. To investigate further the hypothesis that E2 and P modulate NE release in the VMH, and to assess the possible role of this modulation in lordosis behavior, the present experiments measured NE release in the ventrolateral VMH of freely-moving animals using the microdialysis technique.Results Fig. 1 shows a repre...

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Estrous Cyclicity in Mammals

Cited by 32 publications

References 385 publications

Cyclical changes in endogenous levels of oestrogen modulate the induction of LTD and LTP in the hippocampal CA1 region

Cyclical changes in endogenous levels of oestrogen modulate the induction of LTD and LTP in the hippocampal CA1 region

Evidence that Neural Aromatization of Androgen Regulates the Expression of Sexual Behaviour in Female Musk Shrews

Hormonal Activation of Female Sexual Behavior is Accompanied by Hypothalamic Norepinephrine Release

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