Donald W. Pfaff

Luteinizing Hormone-Releasing Factor Potentiates Lordosis Behavior in Hypophysectomized Ovariectomized Female Rats

Subcutaneous injection of luteinizing hormone-releasing factor (LRF) in estrogen-primed hypophysectomized, ovariectomized female rats facilitates the appearance of the lordosis response. The LRF effect on lordosis was seen 90, 180, and 360 minutes after injection. This effect could help to synchronize the females mating behavior with the ovulatory discharge of luteinizing hormone.

Roles of Estrogen Receptor-α Gene Expression in Reproduction-Related Behaviors in Female Mice1

The role of gene expression of the estrogen receptor-␣ form (ER␣) in the regulation of female reproductive behavior was investigated in estrogen receptor knockout (ERKO) mice, deficient specifically for the ER␣, but not the ER␤, gene. Estrogen-or estrogen-plus progesterone-treated gonadectomized ERKO mice did not show any lordosis response. Detailed behavioral analysis revealed that ERKO females were also deficient in sexual behavioral interactions preceding the lordosis response. They were extremely rejective toward attempted mounts by stud male mice, which could not show any intromissions. During resident-intruder aggression tests, gonadally intact ERKO females were more aggressive toward female intruder mice than wild-type (WT) mice. Gonadectomy did not influence the levels of aggressive behavior, and their genotype differences when mice were tested both before and after gonadectomy. However, when mice were tested after gonadectomy for the first time, very few ERKO mice showed aggression. In contrast to aggression, male-type sexual behavior shown by resident mice toward female intruder mice during aggression tests was not different between ERKO and WT mice and was completely abolished after gonadectomy of the resident mice. Finally, it was also found that ERKO females showed greatly reduced levels of parental behavior toward newborn pups placed in their home cage. These changes in parental behavior were not influenced by gonad-ectomy. ERKO females retrieved significantly fewer numbers of pups with longer latencies compared with wild-type (WT) or heterozygous (HZ) littermates when they were tested as gonadally intact or 20 – 65 days after gonadectomy. In addition, during parental behavior tests, a significantly higher percentage of ERKO mice exhibited infanticide compared with WT and HZ mice, which rarely showed infanticide. Taken together, these findings suggest that ER␣ gene expression plays a key role in female mice, not only for sexual behavior but also for other interrelated behaviors, such as parental and aggressive behaviors. In addition, persistence of genotype differences in parental and aggressive behavior after gonadectomy indicates that ER␣ activation during neural developmental processes may also be involved in the regulation of these behaviors. I T IS WELL established that the ovarian steroid, estrogen, regulates female reproduction and lordosis behavior by binding to intracellular estrogen receptors (ER) in the brain. This genomic action of estrogen is assumed to be mediated not only through the classical form of ER (now termed ER␣), but also possibly through the second form of ER, ER␤, which was recently cloned (1, 2). Recent studies have shown that …

Facilitation of the lordosis reflex of female rats from the ventromedial nucleus of the hypothalamus.

1. Effects of electrical stimulation of hypothalamic ventromedial nucleus (v.m.n.) on the lordosis reflex of female rats were examined in ovariectomized and oestrogen‐primed animals with chronically implanted electrodes. 2. Lordosis triggered either by manual cutaneous stimulation or by male mounting, was facilitated by electrical stimulation of the v.m.n. 3 A gradual increase in lordosis performance followed a relatively long period of stimulation; never less than 15 min and usually about 1 hr of stimulation was necessary for maximum facilitation. Following the termination of stimulation, the performance returned gradually to the control level during a 5‐‐8 hr period. 4. The optimal frequency of stimulation was between 10 and 30 Hz. Threshold for effective facilitation was, on the average, 12.5 microA. 5. Stimulation tended to induce larger facilitation when applied to the lateral side of v.m.n. 6. Pre‐treatment with oestrogen was necessary to obtain facilitation by v.m.n. stimulation. The threshold dosage of oestrogen was 2.5 microgram per animal. 7. Stimulation was effective in adrenalectomized rats, in dexamethasone‐primed animals, and in rats pre‐treated with exogenous progesterone. Thus, adrenal prodesterone release is not required for the v.m.n. facilitation of lordosis. 8. Medial preoptic stimulation with the same parameters suppressed the lordosis reflex. 9. The v.m.n. participates in the control of lordosis by a facilitatory output. The delay before facilitation implies that the v.m.n. is not in the direct reflex‐arc for the execution of lordosis. Rather, a summation or interaction process with an unusually long time course is involved.

Silencing of estrogen receptor α in the ventromedial nucleus of hypothalamus leads to metabolic syndrome

Estrogen receptor α (ERα) plays a pivotal role in the regulation of food intake and energy expenditure by estrogens. Although it is well documented that a disruption of ERα signaling in ERα knockout (ERKO) mice leads to an obese phenotype, the sites of estrogen action and mechanisms underlying this phenomenon are still largely unknown. In the present study, we exploited RNA interference mediated by adeno-associated viral vectors to achieve focused silencing of ERα in the ventromedial nucleus of the hypothalamus, a key center of energy homeostasis. After suppression of ERα expression in this nucleus, female mice and rats developed a phenotype characteristic for metabolic syndrome and marked by obesity, hyperphagia, impaired tolerance to glucose, and reduced energy expenditure. This phenotype persisted despite normal ERα levels elsewhere in the brain. Although an increase in food intake preceded weight gain, our data suggest that a leading factor of obesity in this model is likely a decline in energy expenditure with all three major constituents being affected, including voluntary activity, basal metabolic rate, and diet-induced thermogenesis. Together, these findings indicate that ERα in the ventromedial nucleus of the hypothalamus neurons plays an essential role in the control of energy balance and the maintenance of normal body weight.

Deficit in the lordosis reflex of female rats caused by lesions in the ventromedial nucleus of the hypothalamus.

1. The effect of electrolytic lesions of the ventromedial nucleus of the hypothalamus (v.m.n.) on the lordosis reflex has been investigated on ovariectomized female rats. Lesions were made through chronically implanted platinum‐iridium electrodes. 2. V.m.n. lesions did not disrupt lordosis immediately, but induced a gradual decline in the reflex. Lordosis performance reached it minimum no less than 12 hr after the lesion, and typically after 36‐‐60 hr. 3. The magnitude of the lordosis deficit was related to the amount of v.m.n. damage. Destruction of other hypothalamic regions was without appreciable relation to the deficit. Within v.m.n., lesion size in the lateral, but not medial portion was significantly correlated with lordosis deficit. 4. Because of the slow time courses of v.m.n. lesions and stimulation (Pfaff & Sakuma, 1978) effects, it is postulated that the v.m.n. is not part of the direct reflex‐arc for lordosis. Rather, neurones in v.m.n. are likely to exert a tonic hormone‐dependent bias on brain stem reflex paths for this behaviour.

Assessing the molecular genetics of attention networks.

BackgroundCurrent efforts to study the genetic underpinnings of higher brain functions have been lacking appropriate phenotypes to describe cognition. One of the problems is that many cognitive concepts for which there is a single word (e.g. attention) have been shown to be related to several anatomical networks. Recently, we have developed an Attention Network Test (ANT) that provides a separate measure for each of three anatomically defined attention networks.ResultsIn this study we have measured the efficiency of neural networks related to aspects of attention using the ANT in a population of 200 adult subjects. We then examined genetic polymorphisms in four candidate genes (DRD4, DAT, COMT and MAOA) that have been shown to contribute to the risk of developing various psychiatric disorders where attention is disrupted. We find modest associations of several polymorphisms with the efficiency of executive attention but not with overall performance measures such as reaction time.ConclusionsThese results suggest that genetic variation may underlie inter-subject variation in the efficiency of executive attention. This study also shows that genetic influences on executive attention may be specific to certain anatomical networks rather than affecting performance in a global or non-specific manner. Lastly, this study further validates the ANT as an endophenotypic assay suitable for assessing how genes influence certain anatomical networks that may be disrupted in various psychiatric disorders.

An estrogen-dependent four-gene micronet regulating social recognition: A study with oxytocin and estrogen receptor-α and -β knockout mice

Estrogens control many physiological and behavioral processes, some of which are connected to reproduction. These include sexual and other social behaviors. Here we implicate four gene products in a micronet required for mammalian social recognition, through which an individual learns to recognize other individuals. Female mice whose genes for the neuropeptide oxytocin (OT) or the estrogen receptor (ER)-β or ER-α had been selectively “knocked out” were deficient specifically in social recognition and social anxiety. There was a remarkable parallelism among results from three separate gene knockouts. The data strongly suggest the involvement in social recognition of the four genes coding for ER-α, ER-β, OT, and the OT receptor. We thus propose here a four-gene micronet, which links hypothalamic and limbic forebrain neurons in the estrogen control over the OT regulation of social recognition. In our model, estrogens act on the OT system at two levels: through ER-β, they regulate the production of OT in the hypothalamic paraventricular nucleus, and through ER-α, they drive the transcription of the OT receptor in the amygdala. The proper operation of a social recognition mechanism allows for the expression of appropriate social behaviors, aggressive or affiliative.

Possible role for endogenous oxytocin in estrogen-facilitated maternal behavior in rats.

Intracerebroventricular (i.c.v.) infusions of oxytocin (OXY) induce short-latency maternal behavior in estrogen-primed virgin rats. To investigate if brain OXY might have a role in the onset of maternal behavior at parturition, we have used both antisera to OXY and an analog antagonist of OXY, d(CH2)5-8-ornithine-vasotocin, to reduce the activity of endogenous OXY in a pregnancy-terminated preparation which yields reliable short-latency maternal behavior. Sprague-Dawley rats with lateral ventricle cannulae were ovariectomized and hysterectomized on day 16 of gestation; maternal behavior was stimulated by a s.c. injection of estradiol benzoate (EB). Effects of the i.c.v. infusion of antisera to OXY or of the i.c.v. infusion of d(CH2)5-8-ornithine-vasotocin on the latency to respond to pups were tested by presenting pups 48 h after surgery and EB treatment. Behavioral observations were made for the next 5 h and periodically over the next 5 days. Groups receiving either the antisera to OXY or the analog antagonist had significantly longer latencies to respond to pups than did control groups. In a separate experiment, i.c.v. infusion of d(CH2)5-8-ornithine-vasotocin was shown to have no effect on the performance of maternal behavior in lactating rats 5 days postpartum. These results suggest that OXY may have a role in promoting short-latency maternal behavior in steroid-primed female rats, but that it is probably not involved in sustaining this behavior during lactation.

Non-genomic actions of estrogens and their interaction with genomic actions in the brain

Ligands for the nuclear receptor superfamily have at least two mechanisms of action: (a) classical transcriptional regulation of target genes (genomic mechanisms); and (b) non-genomic actions, which are initiated at the cell membrane, which could also impact transcription. Though transcriptional mechanisms are increasingly well understood, membrane-initiated actions of these ligands are incompletely understood. This has led to considerable debate over the physiological relevance of membrane-initiated actions of hormones versus genomic actions of hormones, with genomic actions predominating in the endocrine field. There is good evidence that the membrane-limited actions of hormones, particularly estrogens, involve the rapid activation of kinases and the release of calcium and that these are linked to physiologically relevant scenarios in the brain. We show evidence in this review, that membrane actions of estrogens, which activate these rapid signaling cascades, can also potentiate nuclear transcription in both the central nervous system and in non-neuronal cell lines. We present a theoretical scenario which can be used to understand this phenomenon. These signaling cascades may occur in parallel or in series but subsequently, converge at the modification of transcriptionally relevant molecules such as nuclear receptors and/or coactivators. In addition, other non-cognate hormones or neurotransmitters may also activate cascades to crosstalk with estrogen receptor-mediated transcription, though the relevance of this is less clear. The idea that coupling between membrane-initiated and genomic actions of hormones is a novel idea in neuroendocrinology and provides us with a unified view of hormone action in the central nervous system.

Telemetered Recording of Hormone Effects on Hippocampal Neurons

Frequency-modulated telemetry was used to record the effects of hormones on single-unit activity in the brains of freely moving rats. Corticosterone decreased unit activity in the dorsal hippocampus. Adrenocorticotrophic hormone had the opposite effect.