Biomedical subjects

D W Pfaff

Publications and source records attributed to D W Pfaff.

At least 37 records · Page 2Linked to original sources

PubMed2003

Genetic contributions to generalized arousal of brain and behavior.

We have identified a generalized arousal component in the behavior of mice. Analyzed by mathematical/statistical approaches across experiments, investigators, and mouse populations, it accounts for about 1/3 of the variance in arousal-related measures. Knockout of the gene coding for the classical estrogen receptor (ER-alpha), a ligand-activated transcription factor, greatly reduced arousal responses. In contrast, disrupting the gene for a likely gene duplication product, ER-beta, did not have these effects. A combination of mathematical and genetic approaches to arousal in an experimentally tractable mammal opens up analysis of a CNS function of considerable theoretical and practical significance.

Animals↗

PubMed2003

Impaired discrimination of and aversion to parasitized male odors by female oxytocin knockout mice.

A major cost of social behavior is the increased risk of exposure to parasites, with animals utilizing social information to recognize and avoid infected conspecifics. In mice, females can discriminate between infected and uninfected males on the basis of social cues, displaying aversive responses to the odors of infected males. In the present study, using female mice whose gene for oxytocin (OT) has been selectively deleted (OT knockout mice (OTKO)), we show that at least one normal allele for OT is required for the mediation of the recognition and avoidance of parasitized males. Female wild type (OTWT) and heterozygous (OTHZ) mice distinguished between the odors of individual males infected with the louse, Polyplax serrata, and uninfected males while the KO mice did not. Exposure to the odors of infected males induced analgesia in OTWT and OTHZ females, with OTKO females displaying attenuated analgesia. OTWT and OTHZ females, but not the OTKO females, also distinguished between the odors of novel and familiar infected males and modulated their analgesic responses on the basis of prior familiarity. In an odor choice test, OTWT and OTHZ females displayed a marked initial choice for the odors of uninfected males, whereas the OTKO females showed no consistent choice. This impairment was specific to the odors of infected males. OTKO females displayed normal analgesic responses to another aversive social odor, that of a stressed male, and an aversive non-social odor, that of a cat. The OTKOs had normal non-social olfactory memory, but were impaired in their social odor memory. These findings indicate that a normal OT gene comprises an essential part of the central recognition mechanism whereby females can both reduce the transmission of parasites to themselves and select for parasite-free males.

Animals↗

PubMed2003

Enhanced up-regulation of corticotropin-releasing hormone gene expression in response to restraint stress in the hypothalamic paraventricular nucleus of oxytocin gene-deficient male mice.

The neuropeptide oxytocin is released not only into the blood, but also within the brain in response to various stressors. Accumulating evidence suggests that central oxytocin may play a major role in the regulation of neuroendocrine responses to stress. In the present study, using the oxytocin knockout mouse model, we tested whether oxytocin might act to attenuate stress-induced up-regulation of corticotropin-releasing hormone (CRH) mRNA expression in the brain. The expression of CRH mRNA in the paraventricular nucleus (PVN) after 4 h of restraint stress was examined in oxytocin gene-deficient (OTKO), wild-type and heterozygous male mice using in situ hybridization histochemistry. We found that basal levels of CRH mRNA were not different among the three genotypes. Although restraint stress resulted in a significant increase of CRH mRNA expression in the PVN regardless of genotype, the degree of stress induced-up-regulation was significantly higher in OTKO mice than in wild-type mice. The effects of restraint stress on the expression of the arginine vasopressin (AVP) and the oxytocin genes were also examined. Unlike CRH mRNA, basal expression (in nonstressed control groups) of AVP mRNA in OTKO mice, as well as oxytocin mRNA in heterozygous mice, was significantly lower in the PVN and the supraoptic nucleus than in wild-type mice. After restraint stress, the expression of AVP mRNA was significantly increased in the PVN of OTKO mice compared to the nonstressed control group, whereas the expression of both AVP and oxytocin mRNA were unchanged in the PVN and the supraoptic nucleus of wild-type and heterozygous mice. Finally, in a separate set of mice, restraint stress-induced Fos expression was also examined in several brain regions involved in stress response, including the lateral septum, the bed nucleus of the stria terminalis (BNST), the medial preoptic area, the PVN, the medial and central amygdala using immunohistochemistry. After 90 min of restraint stress, the number of Fos-expressing cells significantly increased in all brain regions examined regardless of genotype. However, the number of stress-induced Fos-expressing cells in the BNST and the medial amygdala of OTKO mice was significantly lower than in wild-type mice. Collectively, the findings in the present study suggest that oxytocin may regulate stress-induced CRH gene expression in the PVN. Furthermore, neuronal activity in the BNST and the medial amygdala may be involved in this neuroendocrine regulatory system.

Animals↗

PubMed2002

Potentiation of the excitatory action of NMDA in ventrolateral periaqueductal gray by the mu-opioid receptor agonist, DAMGO.

Several lines of evidence have suggested that mu-opioids, generally regarded as inhibitory, also have effects that stimulate neural activity. To look for possible excitatory opioid action in the rat periaqueductal gray (PAG), we first re-examined data from a previous study and found that met-enkephalin could evoke a delayed, sluggish excitation, suggestive of modulation by the opioid on the action of certain excitants. This observation, coupled with other studies that show mu-opioids can modulate NMDA receptor activation, prompted us to perform extracellular recording of the responses of single ventrolateral PAG (vlPAG) neurons in brain slices to DAMGO, a mu-opioid, and to NMDA. When applied alone, DAMGO at nM concentrations, like met-enkephalin, often evoked the delayed excitation and occasionally an inhibition. When applied after a brief exposure to NMDA, DAMGO at doses as low as 0.1 nM potentiated the excitation produced by a subsequent pulse of NMDA. This occurred, depending on cell type, in 23-100% of vlPAG neurons. The potentiating action of DAMGO was blocked by naloxone, suggesting it was mediated by mu-opioid receptors. Characterization of these mu-opioid actions revealed that the potentiation and the delayed excitation, unlike the inhibition, was not blocked by another opioid antagonist, nalmefene, nor by an inhibitor of the G protein of the G(i) class, N-ethylmaleimide. Moreover, the potentiating action was distinct from the inhibition in that it was: (a) enhanced by repeated opioid applications, (b) exhibited low effective doses, (c) had a long time course (minutes to develop and last tens of minutes) and (d) was present in distinct though overlapping cell populations. These data reveal an unconventional action of opioids in PAG neurons, that is, a potentiation of excitation produced by NMDA. This effect appeared mechanistically distinct from opioid inhibition or disinhibition and may be related to established examples of direct opioid excitation. These observations may help understanding behaviorally important mechanisms linked to acute and chronic opioid functions in the vlPAG.

Action Potentials↗

PubMed2002

Estrogen's effects on activity, anxiety, and fear in two mouse strains.

Estrogen has effects on activity levels and emotional reactivity in both humans and rats. In a recent study conducted in ovariectomized (OVX) C57BL/6 (C57) mice we found that treatment with estradiol benzoate (EB) increased anxiety, fear learning, and running wheel activity relative to vehicle control (Veh). The present study was conducted to examine the stability of these findings across mouse strains (C57 and Swiss-Webster; SW), to get a better sense of the magnitude of the anxiety response by reducing baseline anxiety levels, and to discover if EB affects activity levels in a safe environment other than the home-cage running wheel. Mice of both strains treated with EB (s.c. implant, 25 microg in sesame oil, which enters the body over 5 weeks) were more anxious than Veh animals in the open field, elevated plus, and dark-light transition tests. SW animals were less anxious than C57 in the elevated plus. EB-treated animals of both strains were more active in the running wheel than Veh animals, and more active in the test of spontaneous activity in the home cage. EB-treatment also increased fear learning in a step-down avoidance task. EB appears to have a consistent but moderate effect in elevating anxiety and in increasing fear learning in two strains of mice. It is also involved in increasing activity in two different types of locomotion in the safer home cage. We conclude that these results of increased anxiety/fear and increased activity are suggestive of a general increase in arousal, with both sets of responses increasing the likelihood of reproductive behaviors occurring only when the environment predicts success.

Animals↗

PubMed2002

Regulation and expression of progesterone receptor mRNA isoforms A and B in the male and female rat hypothalamus and pituitary following oestrogen treatment.

Progesterone receptors play a central role in neuroendocrine and behavioural regulation. To gain insight into the sex- and tissue-specific regulation of progesterone receptors, protein binding on a progesterone receptor-oestrogen response element and mRNA levels for progesterone receptor (PR)-A and PR-B were compared between female and male rats following oestradiol benzoate replacement treatment in hypothalamic and pituitary tissue. Both male and female pituitary protein extracts demonstrated an increase in nuclear protein binding activity to a progesterone receptor-oestrogen response element following oestradiol benzoate treatment. However, there was a greater difference in total binding activity seen in the female pituitary extracts compared to male pituitary protein extracts. In both cases, reflecting the binding data, oestradiol benzoate pretreatment led to an increase in pituitary PR-B messenger RNA, although this increase was significantly larger in females than in males. Oestradiol benzoate treatment also led to a significant increase in specific binding of hypothalamic nuclear proteins to the progesterone receptor oestrogen response element from both females and male hypothalamic extracts. In addition, PR-B messenger RNA was induced by oestradiol benzoate treatment in the female rat hypothalamus, under circumstances where no PR-A could be detected. The male also demonstrated an increase in PR-B messenger RNA following oestradiol benzoate treatment, with undetectable levels of PR-A, although to a lesser degree than that seen in the female. The predominance of PR-B over PR-A messenger RNA in rat hypothalamus and pituitary, and the quantitative differences between female and male rats, could both contribute to the greater responsiveness of female rats to progesterone with respect to control over luteinizing hormone release from the pituitary, and lordosis behaviour regulated by hypothalamic neurones.

Animals↗

PubMed2001

Differential crosstalk between estrogen receptor (ER)alpha and ERbeta and the thyroid hormone receptor isoforms results in flexible regulation of the consensus ERE.

Crosstalk between nuclear receptors is important for conversion of external and internal stimuli to a physiologically meaningful response by cells. Previous studies from this laboratory have demonstrated crosstalk between the estrogen (ER) and thyroid hormone receptors (TR) on two estrogen responsive physiological promoters, the preproenkephalin and oxytocin receptor gene promoter. Since ERalpha and ERbeta are isoforms possessing overlapping and distinct transactivation properties, we hypothesized that the interaction of ERalpha and beta with the various TR isoforms would not be equivalent. To explore this hypothesis, the consensus estrogen response element (ERE) derived from the Xenopus vitellogenin gene is used to investigate the differences in interaction between ERalpha and beta isoforms and the different TR isoforms in fibroblast cells. Both the ER isoforms transactivate from the consensus ERE, though ERalpha transactivates to a greater extent than ERbeta. Although neither of the TRbeta isoforms have an effect on ERalpha transactivation from the consensus ERE, the liganded TRalpha1 inhibits the ERalpha transactivation from the consensus ERE. In contrast, the liganded TRalpha1 facilitates ERbeta-mediated transactivation. The crosstalk between the TRbeta isoforms with the ERalpha isoform, on the consensus ERE, is different from that with the ERbeta isoform. The use of a TRalpha1 mutant, which is unable to bind DNA, abolishes the ability of the TRalpha1 isoform to interact with either of the ER isoforms. These differences in nuclear receptor crosstalk reveal an important functional difference between isoforms, which provides a novel mechanism for neuroendocrine integration.

Animals↗

PubMed2001

Early membrane estrogenic effects required for full expression of slower genomic actions in a nerve cell line.

Interpretations of steroid hormone actions as slow, nuclear, transcriptional events have frequently been seen as competing against inferences of rapid membrane actions. We have discovered conditions where membrane-limited effects potentiate later transcriptional actions in a nerve cell line. Making use of a two-pulse hormonal schedule in a transfection system, early and brief administration of conjugated, membrane-limited estradiol was necessary but not sufficient for full transcriptional potency of the second estrogen pulse. Efficacy of the first pulse depended on intact signal transduction pathways. Surprisingly, the actions of both pulses were blocked by a classical estrogen receptor (ER) antagonist. Thus, two different modes of steroid hormone action can synergize.

Alkaloids↗

PubMed2001

Co-expression of estrogen and thyroid hormone receptors in individual hypothalamic neurons.

Estrogen receptors (ER) and thyroid hormone receptors (TR) are members of the nuclear receptor family of transcription factors that induce or repress the expression of target genes. Previous behavioral studies in female rodents have demonstrated that thyroid hormones can antagonize the effects of estrogen in the central nervous system (CNS), particularly by attenuating estrogen's ability to facilitate reproductive behaviors. Additional molecular studies have suggested a mechanism for this antagonism by showing that ligand-activated ER alpha and TRs have the potential to interact in their transcriptional controls. Although the expression patterns of ER alpha and TRs in the rodent brain appear to overlap in behaviorally relevant areas, it remained to be determined whether these two classes of proteins coexist in vivo at the level of single neurons. To address this possibility, we employed a highly sensitive double-label in situ hybridization technique using digoxigenin and (35)S-labeled cRNA probes to analyze, in detail, the expression of ER alpha mRNA with TR alpha 1 and TR alpha 2 mRNAs in the same neurons of the ovariectomized (OVX) adult mouse brain. Our results demonstrate that a large majority of the ER alpha-positive neurons also expresses TR alpha 1 and TR alpha 2 mRNAs. Quantitative examination of the cellular expression in the ventromedial and arcuate nuclei of the hypothalamus (VMH and Arc) showed that 81.5% and 80.5% of the neurons endowed with ER alpha mRNA also contain TR alpha 1 and TR alpha 2 mRNAs, respectively. In the amygdala, more than 60.5% and 67% of ER alpha-positive cells also contain TR alpha 1 and TR alpha 2 mRNAs, respectively. These findings provide the first anatomical evidence that ER and TR can be found in the same neurons, including hypothalamic neurons. This coexpression of ER alpha and TR provides the cellular basis for a new level of neuronal integration in a brain region where estrogens control female reproductive behaviors.

Amygdala↗

PubMed2001

Molecular analysis of estrogen induction of preproenkephalin gene expression and its modulation by thyroid hormones.

Estrogen receptors (ER) and thyroid hormone receptors (TR) are ligand-dependent nuclear transcription factors. Estrogen-induced preproenkephalin (PPE) gene expression in the hypothalamus is directly related to estrogen-induced lordosis behavior in the rat. In the present study, we showed that the PPE mRNA level in the ventromedial hypothalamus of female rats was significantly decreased by ovariectomy. This decrease was reversed by estrogen replacement in a dose- and time-dependent manner. Using transient transfection and electrophoretic mobility shift assays (EMSA), functional estrogen response elements (ERE) were identified between -437 and -145 base pairs (bp) of the rat PPE gene promoter region. Two ERE-like elements are present between -405 and -364 of the rat PPE gene promoter, which bind ERalpha as demonstrated by EMSA. Estrogen produced a dose-dependent increase in CAT activity in cotransfection assays with ERalpha expression vector and a 437PPE-CAT reporter construct containing 437 bp of the rat PPE gene promoter and the CAT reporter gene. This estrogen-induced PPE promoter activity was inhibited by liganded-TR in transient cotransfection assays. Analysis of DNA-protein interactions by EMSA revealed that both ERalpha and TR (alpha1 and beta1) could bind to the EREs in the rat PPE gene promoter. Furthermore, estrogen induction of PPE mRNA in the ventromedial hypothalamus of the ovariectomized female rat was significantly attenuated by concomitant administration of triiodothyronine. These results suggest that estrogen regulation of the hypothalamic PPE gene expression is mediated through an estrogen-receptor complex directly interacting with the functional EREs in its promoter region; and that this estrogen effect can be modified by thyroid hormones.

Animals↗

PubMed2001

Expression of the SCAMP-4 gene, a new member of the secretory carrier membrane protein family, is repressed by progesterone in brain regions associated with female sexual behavior.

Rodent female reproductive behavior is facilitated by the genomic targets of estrogen (E) and progesterone (P) in neuroendocrine regions of the brain. Using the differential display-PCR technique to identify these targets we discovered a novel hormone-sensitive mRNA in the female rat brain that is substantially reduced in the ventromedial hypothalamus (VMH) after 3 h of P treatment, following 24 h of E priming. Northern blots show that it is a single transcript of approximately 1.7 kb. The sequence of the corresponding full-length cDNA indicates that this gene is the rat homolog of mouse SCAMP-4, the fourth member identified in a family of proteins known as secretory carrier membrane proteins (SCAMPs). In situ hybridization studies show that SCAMP-4 mRNA is relatively low throughout the rat forebrain, with the highest levels observed in the VMH, habenula and hippocampus. The SCAMP-4 message is also less abundant in the habenula and VMH during proestrus, when circulating levels of E and P are at their peak, than during diestrus-1 when circulating hormone levels are low. Amino acid sequence analysis indicates that SCAMP-4 lacks the putative calcium binding and leucine zipper structures, as well as protein-protein interacting NPF domains common among most SCAMP family members, but is the only member identified to date to contain a putative protein kinase C (PKC) phosphorylation site. Fluorescent microscopy of cells transfected with a SCAMP-4/GFP fusion construct reveals distinct fluorescence in subcellular aggregates that may contain secretory vesicles. In addition to our results in the VMH, the finding of high levels of SCAMP-4 message in the habenula, a brain area rich in mast cells, together with previous reports linking mast cell secretion with courtship behavior also suggest a possible role for SCAMP-4 in reproductive behaviors associated with mast cell activity in the central nervous system (CNS).

Amino Acid Sequence↗

PubMed2001

Female preproenkephalin-knockout mice display altered emotional responses.

The endogenous opioid system has been implicated in sexual behavior, palatable intake, fear, and anxiety. The present study examined whether ovariectomized female transgenic preproenkephalin-knockout (PPEKO) mice and their wild-type and heterozygous controls displayed alterations in fear and anxiety paradigms, sucrose intake, and lordotic behavior. To examine stability of responding, three squads of the genotypes were tested across seasons over a 20-month period. In a fear-conditioning paradigm, PPEKO mice significantly increased freezing to both fear and fear + shock stimuli relative to controls. In the open field, PPEKO mice spent significantly less time and traversed significantly less distance in the center of an open field than wild-type controls. Further, PPEKO mice spent significantly less time and tended to be less active on the light side of a dark-light chamber than controls, indicating that deletion of the enkephalin gene resulted in exaggerated responses to fear or anxiety-provoking environments. These selective deficits were observed consistently across testing squads spanning 20 months and different seasons. In contrast, PPEKO mice failed to differ from corresponding controls in sucrose, chow, or water intake across a range (0.0001-20%) of sucrose concentrations and failed to differ in either lordotic or female approach to male behaviors when primed with estradiol and progesterone, thereby arguing strongly for the selectivity of a fear and anxiety deficit which was not caused by generalized and nonspecific debilitation. These transgenic data strongly suggest that opioids, and particularly enkephalin gene products, are acting naturally to inhibit fear and anxiety.

Animals↗

PubMed2001

Reproduction-related behaviors of Swiss-Webster female mice living in a cold environment.

Based on a molecular neuroendocrine theory about cold environments, thyroid hormone levels, and liganded thyroid hormone receptor interference with estrogen receptor function, experiments were designed to test female mouse reproductive behaviors in the cold. Because natural seasonal temperature declines would usually be associated with decreased photoperiods and reduced food supplies, we combined cold temperatures with short days and metabolic challenge. The simplest hypothesis was that lordosis quotients would be significantly reduced as a result of cold temperatures. That hypothesis was denied. Instead, female approaches to the stud male declined. Because cold temperatures also led to significant reductions of activity in locomotor wheels, a straightforward reduction of activity could explain the female's behavior during mating tests. We suggest that cold temperatures accompanied by reduced photoperiod and reduced metabolic fuel can reduce overall activity in female mice, thus indirectly blocking untimely reproductive behaviors.

Adaptation, Physiological↗

PubMed2001

Effects of the phytoestrogen coumestrol on locomotor and fear-related behaviors in female mice.

Effects of the estrogenic plant isoflavonoid coumestrol (COUM) on locomotor activity and fear-related behaviors in both the absence and the presence of estradiol benzoate (EB) were examined in adult ovariectomized Swiss-Webster mice. In a running wheel paradigm conducted over 10 days, with treatment beginning 12 days prior to testing, daily subcutaneous (sc) injections of 10 microg of COUM did not influence locomotor activity, whereas even the low dose of EB supplied by sc Silastic implant (2.5 microg lasting 5 weeks) produced a significant increase in locomotor activity over animals receiving vehicle alone. In animals receiving both COUM and EB, locomotor activity was significantly diminished compared to the activity observed in animals receiving EB alone. The same animals were also tested in three behavioral paradigms having known activity and fear components (open field, dark/light transition, elevated plus-maze). COUM did not produce significant effects in these assays. However, in an associative fear learning paradigm (fear conditioning), COUM produced significantly less freezing ("fearfulness") in the conditioned fear task than with animals receiving vehicle or a low dose of EB, which did not differ from each other. Unlike EB, which has comparable affinities for estrogen receptor (ER) alpha and ER beta, COUM has a higher affinity for ER beta than for ER alpha. COUM might disrupt estrogen-enhanced locomotor activity by altering the dynamic by which EB acts on the brain through these two ER isoforms. The conditioned fear result suggests that COUM may produce additional effects through alternative pathways.

Animals↗

PubMed2001

Effects of estrogen on activity and fear-related behaviors in mice.

Estrogen has been shown to affect nonreproductive behaviors in humans and rodents, including anxiety, fear, and activity levels. Rat studies have shown increases and decreases in these behaviors. Inconsistencies may be due to differences in testing conditions and the extent to which each test measures anxiety, fear, or activity. Few mouse studies have been performed. The present study was conducted to address these issues by examining the effect of estradiol benzoate (EB) in ovariectomized (OVX), C57BL/6 mice on a range of behavioral paradigms measuring anxiety [open field (OF), dark-light transition (DLT), elevated plus maze (EP)], activity [running wheel (RW)], and conditioned fear learning (FCon). In OF, vehicle (Veh) animals spent more time in the center than EB-treated animals and were more active overall. In DLT, Veh animals were more active than EB-treated animals in both the dark and light compartments and made more transitions between the two. In EP, Veh animals entered a greater number of arms. During FCon, EB animals froze more than Veh to the conditioned stimulus. In contrast, in the home cage RW, EB animals were more active than Veh. Factor analysis was used to characterize intertask correlations of females' behavior and to explore the possibility that estrogen may have an impact on a general arousal factor. In sum, estrogen treatment heightened fear responses in a range of fear and anxiety-provoking situations (OF, DLT, EP, and FCon), while increasing activity in the safer RW. We suggest that EB treatment may result in a generally more aroused animal.

Animals↗

PubMed2001

Ultrastructural evidence for enkephalin mediated disinhibition in the ventromedial nucleus of the hypothalamus.

The ventromedial nucleus of the hypothalamus (VMN) regulates the estrogen-dependent appearance of female mating behavior, lordosis. Accumulating evidence suggests that estrogen might exert its control over lordosis by acting, in part, on neurons that contain enkephalin in the VMN. The expression of the enkephalin precursor gene is robustly stimulated by estrogen and is correlated with the later appearance of lordosis. GABA has also been implicated as an important neurotransmitter for the appearance of lordosis. Because enkephalin is thought to act in several brain areas to modulate the activity of GABAergic neurons, we studied the ultrastructural morphology and relationship between neurons containing these neurochemicals using dual-labeling immunocytochemistry in ovariectornized rats, half of which received estrogen replacement. Immunolabeling for enkephalin was almost always detected within axon terminals (695 axonal profiles sampled), while GABA immunoreactivity was more often localized to cell bodies and dendrites (191 profiles), than to axons (63 profiles). Axon terminals containing enkephalin immunolabeling provided a major innervation to soma or dendrites containing GABA. That is, over one third (94/245) of the axon terminals in contact with GABA-immunoreactive dendrites contained enkephalin. Furthermore, these GABA-immunoreactive dendrites accounted for a fifth of the somatodendritic processes associated with enkephalin-containing axon terminals. These findings support the hypothesis that enkephalin may act in the VMN by inhibiting GABAergic neurons, which could result in the disinhibition of neural circuits relevant for lordosis.

Animals↗

PubMed2001

Deficits in E2-dependent control of feeding, weight gain, and cholecystokinin satiation in ER-alpha null mice.

To test the role of gene expression of the classical ER (ER alpha) in the inhibitory effects of E on food intake and body weight, we ovariectomized and administered E2 benzoate (75 pg/d) or vehicle to wild-type (WT) mice and mice with a null mutation of ER alpha (alpha ERKO). Mice were ovariectomized at age 9 wk, at which time there was no significant effect of genotype on food intake or body weight. During an 18-d test after recovery from ovariectomy, vehicle-treated WT mice increased daily food intake and gained more body weight than E2-treated WT mice, whereas food intake and body weight gain were not different in E2- and vehicle-treated alpha ERKO mice. Carcass analysis revealed parallel changes in body lipid content, but not water or protein content. Because an increase in the potency of the peripheral cholecystokinin (CCK) satiation-signaling system mediates part of E2's influence on feeding in rats, the influence of ip injections of 250 microg of the selective CCK(A) receptor antagonist devazepide was then tested. Devazepide increased 3-h food intake in E2-treated WT mice, but was ineffective in both groups of alpha ERKO mice. Furthermore, ip injections of 4 microg/kg CCK-8 increased the number of cells expressing c-Fos immunoreactivity in the nuclei of the solitary tract of E2-treated WT mice more than it did in vehicle-treated WT mice, whereas E2 had no such effect in alpha ERKO mice. Thus, ER alpha is necessary for normal responsivity of food intake, body weight, adiposity, and the peripheral CCK satiation-signaling system to E2 in mice, and ER beta is not sufficient for any of these effects. This is the first demonstration that ER alpha gene expression is involved in the estrogenic control of feeding behavior and weight regulation of female mice.

Animals↗

PubMed2000

Abolition of male sexual behaviors in mice lacking estrogen receptors alpha and beta (alpha beta ERKO).

Male mice with a knockout of the estrogen receptor (ER)-alpha gene, a ligand-activated transcription factor, showed reduced levels of intromissions and no ejaculations whereas simple mounting behavior was not affected. In contrast, all components of sexual behaviors were intact in male mice lacking the novel ER-beta gene. Here we measure the extent of phenotype in mice that lack both ER-alpha and ER-beta genes (alphabetaERKO). alphabetaERKO male mice did not show any components of sexual behaviors, including simple mounting behavior. Nor did they show ultrasonic vocalizations during behavioral tests with receptive female mice. On the other hand, reduced aggressive behaviors of alphabetaERKO mice mimicked those of single knockout mice of ER-alpha gene (alphaERKO). They showed reduced levels of lunge and bite aggression, but rarely showed offensive attacks. Thus, either one of the ERs is sufficient for the expression of simple mounting in male mice, indicating a redundancy in function. Offensive attacks, on the other hand, depend specifically on the ER-alpha gene. Different patterns of natural behaviors require different patterns of functions by ER genes.

Aggression↗