Participation of the nitric oxide pathway in lordosis induced by apelin-13 in female rats.

The present study investigated the participation of the nitric oxide pathway in facilitating lordosis behavior induced by intrahypothalamic administration of apelin-13 in ovariectomized rats primed with estradiol benzoate (EB). The experiments involved the administration of a nitric oxide synthase inhibitor (L-NAME) or a nitric oxide-dependent, soluble guanylyl cyclase inhibitor (ODQ), and an inhibitor of protein kinase G (KT5823) to the ventromedial hypothalamus (VMH) of EB-primed rats 30 min before infusion of apelin-13 (0.75 µg/µl). This dose of apelin-13 consistently induces lordosis behavior at 30 min, 120 min, and 240 min following infusion. Results showed that injections of either L-NAME or KT5823 significantly reduced the lordosis induced by apelin at 120 and 240 min. However, VMH infusion of ODQ 30 min before apelin-13 infusion reduced but did not significantly inhibit, the lordosis elicited by this peptide at the same time points. We conclude that the nitric oxide pathway in the VMH plays an important role in lordosis induced by apelin-13 in EB-primed rats.

Estradiol and progesterone-induced lordosis behavior is modulated by both the Kisspeptin receptor and melanin-concentrating hormone in estradiol benzoate-primed rats.

Intracerebroventricular (ICV) administration of estradiol benzoate (E2B) and progesterone (P) induces intense lordosis behavior in ovariectomized rats primed peripherally with E2B. The present study tested the hypothesis that the Kisspeptin (Kiss) and melanin-concentrating hormone (MCH) pathways regulate female sexual behavior induced by these steroid hormones. In Experiment 1, we tested the relevance of the Kiss pathway by ICV infusion of its inhibitor, kiss-234, before administration of E2B or P in estrogen-primed rats. Lordosis induced by E2B alone or with the addition of P was reduced significantly at 30, 120, and 240 min. In Experiment 2, ICV infusion of MCH 30 min before E2B or P significantly reduced lordosis in rats primed with E2B alone. These data support the hypothesis that the Kiss and MCH pathways, which can release or modulate gonadotropin-releasing hormone (GnRH), are involved in E2B- and P-induced lordosis.

Apelin-13 facilitates lordosis behavior following infusions to the ventromedial hypothalamus or preoptic area in ovariectomized, estrogen-primed rats.

In normal hormonal conditions, increased neuronal activity in the ventromedial hypothalamus (VMH) induces lordosis whereas activation of the preoptic area (POA) exerts an opposite effect. In the present work, we explored the effect of bilateral infusion of different doses of the apelin-13 (0.37, 0.75, 1.5, and 15 µg) in both brain areas on the expression of lordosis behavior. Lordosis quotient and lordosis reflex score were performed at 30, 120, and 240 min. Weak lordosis was observed following the 0.37 µg dose of apelin-13 at 30 min in the VMH of EB-primed rats; however, the rest of the doses induced significant lordosis relative to the control group. At 120 min, all doses induced lordosis behavior, while at 240 min, the highest dose of 15 µg did not induce significant differences. Interestingly, only the 0.75 µg infusion of apelin in the POA induced significant lordosis at 120 and 240 min. These results indicate that apelin-13 acts preferably in HVM and slightly in POA to initiate lordosis behavior in estrogen-primed rats.

Oxytocin induces lordosis behavior in female rats through the prostaglandin E2/GnRH signaling system.

Intracerebroventricular (icv) administration of oxytocin (OT) induces robust lordosis behavior (lordosis quotient and lordosis intensity) in estrogen-primed rats. The present study explored the hypothesis that the OT-Prostaglandin E2-GnRH pathway (a pathway produced in astrocytes) is involved in the facilitation of lordosis behavior by icv infusion of OT (2 µg). In Experiment 1, we tested the involvement of the OT receptor (OTR) by infusion of the OTR antagonist, atosiban (ATO). OT-induced lordosis was significantly reduced at both 30 and 120 min by prior infusion of ATO. In Experiment 2, we studied the effects of aspirin (COX2 inhibitor) and ONO-AE3-208 (ONO; EP4 prostaglandin receptor antagonist) on OT-induced lordosis. Infusions of both compounds diminished OT-induced lordosis at both 120 and 240 min. In Experiment 3, the involvement of the GnRH-1 receptor inhibitor antide on OT-induced lordosis was evaluated. Antide significantly inhibited OT-induced lordosis at all times tested. These data indicate that the OT/PGE2/GnRH pathway is involved in the expression of OT-induced lordosis behavior, an effect that may be occurring directly in hypothalamic astrocytes.

Protein kinase inhibitors infused intraventricularly or into the ventromedial hypothalamus block short latency facilitation of lordosis by oestradiol.

An injection of unesterified oestradiol (E2 ) facilitates receptive behaviour in E2 benzoate (EB)-primed, ovariectomised female rats when it is administered i.c.v. or systemically. The present study tested the hypothesis that inhibitors of protein kinase A (PKA), protein kinase G (PKG) or the Src/mitogen-activated protein kinase (MAPK) complex interfere with E2 facilitation of receptive behaviour. In Experiment 1, lordosis induced by i.c.v. infusion of E2 was significantly reduced by i.c.v. administration of Rp-cAMPS, a PKA inhibitor, KT5823, a PKG inhibitor, and PP2 and PD98059, Src and MAPK inhibitors, respectively, between 30 and 240 minutes after infusion. In Experiment 2, we determined whether the ventromedial hypothalamus (VMH) is one of the neural sites at which those intracellular pathways participate in lordosis behaviour induced by E2 . Administration of each of the four protein kinase inhibitors into the VMH blocked facilitation of lordosis induced by infusion of E2 also into the VMH. These data support the hypothesis that activation of several protein kinase pathways is involved in the facilitation of lordosis by E2 in EB-primed rats.

Effects of fluoride on morphology, growth, development, and thyroid hormone of Chinese toad (Bufo gargarizans) embryos.

Excessive fluoride in natural water ecosystem has the potential to detrimentally affect amphibians, but little is known of such effects or underlying mechanisms in Bufo gargarizans embryos. In the present study, the effects of fluoride exposure on B. gargarizans embryos were investigated. First, fluoride teratogenic experiment showed that the 9 days EC50 of fluoride on B. gargarizans embryos was 177.62 mg/L. Then, we studied the sublethal effects of fluoride on B. gargarizans embryos at control, 0.7, 4.1, 19.6, 41.9, and 62.7 mg/L fluoride concentration. Malformation, growth, and development of embryos were monitored, and type 2 and 3 iodothyronine deiodinase (Dio2 and Dio3), thyroid hormone receptors (TRα and TRß) mRNA levels were measured. Our results showed the morphological malformations, such as tail curvature (lordosis), edema, cuticularized ciliated cells, and hyperplasia were occurred during fluoride exposure. Growth and development were all inhibited at 19.5, 41.9, and 62.7 mg/L fluoride-treated groups after 9 days' exposure. According to real-time PCR results, exposure to fluoride upregulated Dio3 and TRß mRNA expression and downregulated Dio2 and TRα mRNA level. All above indicated that excessive fluoride could induce morphology malformations, inhibit embryonic growth and development, and disrupt the normal function of maternal thyroid hormone in B. gargarizans embryos. Environ. Mol. Mutagen. 59:123-133, 2018. © 2017 Wiley Periodicals, Inc.

Endosulfan affects health variables in adult zebrafish (Danio rerio) and induces alterations in larvae development.

Adult zebrafish (Danio rerio) were exposed to 0 (control), 0.16 or 0.48µg/L of the insecticide, endosulfan, for 28days. Haematology, whole body ions, thiobarbituric acid reactive substances (TBARS), Na(+)K(+)-ATPase, organ histology and reproduction were assessed in adults. The resulting offspring were examined for latent effects on development (heart rate and morphometrics). On day 14, adult fish exposed to 0.16µg/L endosulfan showed significantly lower red blood cell counts than those exposed to 0.48µg/L endosulfan; adult fish exposed to 0.16 ug/L also showed elevated TBARS compared to controls. Both concentrations of endosulfan caused a 4.0 fold increase in Na(+)K(+)-ATPase activity compared to controls (ANOVA, p<0.05). On day 14, the livers of fish exposed to endosulfan had fewer, enlarged hepatocytes, with cell diameters greater than the controls (ANOVA, p<0.05). Morphological alterations in the progeny of fish exposed to endosulfan were observed. Heart beat frequency was significantly lower in larvae from exposed adults to 0.16 µg/L compared to the control (ANOVA, p<0.05). These findings show that sublethal exposure to endosulfan causes adverse sublethal effects in adult D. rerio, and effects on the development of their offspring.

Impact of strontium on skeletal deformities in Baltic cod (Gadus morhua callaris L.).

A study was conducted to examine spinal deformities such as lordosis, scoliosis, and dwarfism in cod (Gadus morhua callaris L.) that were caught in the southern Baltic. The bone tissue of the spine and the muscle of the deformed cod were analyzed for concentration of macroelements (Sr, Ca and P) and toxic metals (Cd, Pb and Hg). Healthy specimens of the same body length that were caught in the same hauls were also tested, and these comprised the reference material. The study was undertaken to verify the hypothesis that lowered values of Ca/Sr and P/Sr ratios caused skeletal deformities. Toxic metals were also tested to determine whether they had an impact on the deformities of cod inhabiting Baltic waters. In cod with deformities, a significant decrease in Ca/Sr ratios were noted in 86% of the spine and 97% of the muscle. Decreases in the values of the P/Sr ratios were confirmed in 57% of the bone tissue and 78% of the muscle tissue of individuals with skeletal deformities. Toxic metals (Cd, Pb and Hg) occurred in the bone and muscle tissues of deformed and healthy cod on the low levels. It was not differences in concentrations of these elements, and thus could not have had an impact on the occurrence of deformities. Skeletal deformities could have resulted from lowered values of the Ca/Sr and P/Sr ratios of the spinal bone and muscle tissues of cod. Lower values of these coefficients should be linked to the varied salinity (5-21‰) and strontium (5-15Bqm(-3)) concentrations of Baltic waters.

Fluoranthene, but not benzo[a]pyrene, interacts with hypoxia resulting in pericardial effusion and lordosis in developing zebrafish.

Previous research has documented several PAHs that interact synergistically, causing severe teratogenicity in developing fish embryos. The coexposure of CYP1A inhibitors (e.g. FL or ANF) with AHR agonists (e.g. BaP or BNF) results in a synergistic increase in toxicity. As with chemical CYP1A inhibitors, it has also been shown that CYP1A morpholinos exacerbate BNF-induced embryotoxicity. We hypothesized that a hypoxia-induced reduction in CYP1A activity in BNF or BaP-exposed zebrafish embryos would similarly enhance pericardial effusion and other developmental abnormalities. BaP, BNF, ANF, and FL exposures, both individually and as BaP+FL or BNF+ANF combinations, were performed under hypoxia and normoxia. CYP1A activity in the BaP+hypoxia and BNF+hypoxia embryos was reduced by approximately 60% relative to normoxia embryos. Although CYP1A activity was significantly reduced, we did not observe any increase in pericardial effusion in either group. An unexpected yet particularly interesting result of these experiments was the observed interaction of both FL and ANF with hypoxia. Relatively high, yet environmentally relevant concentrations of FL (100-500 microg L(-1)) interact with moderate hypoxia (7.3% DO) through an unknown mechanism, resulting in pericardial effusion and severe lordosis. Additionally, ANF exposures (100 microg L(-1)) which are not normally teratogenic caused dramatic pericardial effusion, but not lordosis, when embryos were coexposed to hypoxia. These results suggest that reduced CYP1A activity may not exclusively underlie observed developmental toxicity, and that hypoxia may exacerbate the developmental toxicity of some PAH mixtures.

Omphalocele induction in the chick embryo by administration of cadmium.

BACKGROUND: Ventral body wall (VBW) defects occur in 1:2000 live births. We examined the association of VBW defect with somite abnormality and lordosis in the chick using in vitro and in ovo methods. METHODS: Explanted chick embryos were treated at 60 hours with 50 microL sodium acetate or 0.001% cadmium acetate solution to produce VBW defects. Mortality and abnormality rates were assessed. A further cohort of chicks was treated in ovo by dropping 50 microL 0.001% to 0.01% cadmium acetate onto the embryo and allowing development to 16.5 days for further assessment of the defect and skeletal staining with alcian blue and alizarin red. RESULTS: Cadmium treatment at 24 hours induced VBW defects in chicks treated in both shell-less culture and in ovo. Material herniating through the VBW defects was covered by a membrane in all fresh specimens. Membrane removal revealed large defects containing liver and bowel. These criteria clearly indicate that the defect observed is an omphalocele. Affected embryos had reduced somite numbers within 24 hours. Chicks exhibiting exomphalos at 16.5 days invariably had lumbosacral lordosis. CONCLUSIONS: The cadmium-treated chick embryo is a reliable model for exomphalos. A positive association was found between exomphalos and lumbar lordosis in the chick.

Metabolic effects of dinoseb, diazinon and esfenvalerate in eyed eggs and alevins of Chinook salmon (Oncorhynchus tshawytscha) determined by 1H NMR metabolomics.

Pesticide pulses in the Sacramento River, California, originate from storm-water discharges and non-point source aquatic pollution that can last from a few days to weeks. The Sacramento River and its tributaries have historically supported the majority of California's Chinook salmon (Oncorhynchus tshawytscha) spawning grounds. Three pesticides currently used in the Sacramento Valley-- dinoseb, diazinon, and esfenvalerate-- were chosen to model the exposure of salmon embryos to storm-water discharges. Static-renewal (96 h) exposures to eyed eggs and alevins resulted in both toxicity and significant changes in metabolism assessed in whole-embryo extracts by (1)H nuclear magnetic resonance (NMR) spectroscopy based metabolomics and HPLC with UV detection (HPLC-UV). The 96-h LC(50) values of eyed eggs and alevins exposed to dinoseb were 335 and 70.6 ppb, respectively, and the corresponding values for diazinon were 545 and 29.5 ppm for eyed eggs and alevins, respectively. The 96-h LC(50) of eyed eggs exposed to esfenvalerate could not be determined due to lack of mortality at the highest exposure concentration, but in alevins was 16.7 ppb. All esfenvalerate exposed alevins developed some degree of lordosis or myoskeletal abnormality and did not respond to stimulus or exhibit normal swimming behavior. ATP concentrations measured by HPLC-UV decreased significantly in eyed eggs due to 250 ppb dinoseb and 10 and 100 ppb esfenvalerate (p < 0.05). Phosphocreatine, as measured by HPLC-UV, decreased significantly in eyed eggs due to 250 ppb dinoseb, 10 and 100 ppb esfenvalerate, and 100 ppm diazinon (p < 0.05). Principal components analyses of (1)H NMR metabolite fingerprints of eyed egg and alevin extracts revealed both dose-dependent and mechanism of action-specific metabolic effects induced by the pesticides. Furthermore, NMR based metabolomics proved to be more sensitive than HPLC-UV in identifying significant changes in sublethal metabolism of pesticide exposed alevins. In conclusion, we have demonstrated several benefits of a metabolomics approach for chemical risk assessment, when used in conjunction with a fish embryo assay, and have identified significant metabolic perturbations to the early life stages of Chinook salmon by currently used pesticides.

Estrogen can act via estrogen receptor alpha and beta to protect hippocampal neurons against global ischemia-induced cell death.

Estradiol at physiological concentrations intervenes in apoptotic death cascades and ameliorates neuronal death in experimental models of focal and global ischemia. The cellular targets that mediate estradiol protection of hippocampal neurons in global ischemia are, however, unclear. The present study examined the hypothesis that estradiol protects hippocampal neurons in ovariectomized rats via estrogen receptor (ER)alpha and/or beta. Estradiol (14 d pretreatment) afforded robust protection of CA1 neurons against global ischemia-induced death. The broad-spectrum ER antagonist ICI 182,780 (intracerebroventricularly, 0 and 12 h after ischemia) abolished estrogen protection, consistent with a role for ERs. To evaluate the potential roles of ERalpha vs. ERbeta in estrogen protection, we administered subtype-selective agonists for 14 d before and 7 d after ischemia. The ERalpha-selective agonist propyl pyrazole triol (PPT, 10 mg/kg) and ERbeta-selective agonist WAY 200070-3 (1 mg/kg) produced nearly complete protection of CA1 neurons in approximately 50% of the animals. PPT, but not WAY 200070-3, at doses used for protection, elicited lordosis, induced negative feedback inhibition of LH release, and reduced weight gain. These findings establish the efficacy of the PPT dose in neuroendocrine assays and specificity of WAY 200070-3 for ERbeta. We also examined the ability of estradiol and neuronal injury to regulate ERalpha and ERbeta expression. Both estradiol and global ischemia markedly increased ERalpha, but not ERbeta, protein in CA1. These data indicate that estradiol can act via ERalpha and ERbeta to protect CA1 neurons from global ischemia-induced death and that both estradiol and global ischemia modulate ERalpha expression in hippocampal CA1.

Chronic effects of dietary selenium on juvenile Sacramento splittail (Pogonichthys macrolepidotus).

The chronic effects of dietary selenium (Se) exposure in juvenile Sacramento splittail (Pogonichthys macrolepidotus) were investigated in the laboratory. A total of 960 (40 fish per tank, 3 tanks per diet) 7-month-old juvenile splittail were fed one of eight Purified-Casein diets supplemented with selenized yeast for 9 months in a flow-through system. These diets contained the following: 0.4 (control), 0.7, 1.4, 2.7, 6.6, 12.6, 26.0, and 57.6 mg of Se kg(-1) dry weight. Survival, Se tissue concentration, growth, gross morphology, and liver histopathology were assessed at 5- and 9-month of exposure. Mortalities occurred only in the two highest Se treatments and were accounted for 8.3 and 18.3% at 5-month and 10.0 and 34.3% at 9-month, respectively. Liver and muscle Se concentration were significantly correlated with dietary Se concentration. Fish exposed to 0.4-12.6 mg of Se kg(-1) diets had reached equilibrium in liver Se concentration by 5 month. Splittail fed diets at concentrations > or =26.0 mg of Se kg(-1) had not reached equilibrium in liver, and muscle Se concentrations and grew significantly slower (p < 0.05) at 5- and 9-month exposure. Se-induced deformities were observed in fish fed > or =2.7 mg of Se kg(-1) diets at 5-month and in fish fed > or =0.7 mg of Se kg(-1) diets at 9-month. Fish fed 26.0 and 57.6 mg of Se kg(-1) diets had higher liver lesion scores at 5-month while fish fed 6.6 and 57.6 mg of Se kg(-1) diet had higher liver lesion scores at 9-month. Results indicate that survivals, growth, changes of tissue Se concentrations, and histopathology of juvenile splittail were dose-dependent, but their response thresholds to dietary Se concentrations differed and depended on treatment concentrations and duration of exposure. Chronic exposure to 6.6 mg of Se kg(-1) diet induced deleterious health effects that can potentially impact survival of juvenile splittail.

Oestrogen modulates cholecystokinin: opioid interactions in the nervous system.

Responses of the nervous system to introceptive and extroceptive inputs depend upon the state of the brain. Oestrogen has the ability to modulate brain state and dramatically alter interactions among neural circuits to influence an organism's responses to given stimuli. Cholecystokinin (CCK) and endogenous opioid peptides (EOP) have a wide and parallel distribution in the nervous system. Their reciprocal interactions regulate a diverse physiology including reproduction, cortical function and nociception. The actions of CCK and EOP are diametrically opposed, in many regions. For example, when opioids inhibit reproductive behaviour or nociception, CCK facilitates. Because oestrogen is a powerful regulator of the expression of CCK and EOP, we examined whether oestrogen-state also modulated the interactions of these neuropeptides. In this paper we present new data and review previous work that demonstrates oestrogen modulation of functional CCK-opioid interactions that regulate reproductive behaviour, cortical function and nociception.

Effect of cadmium in the zinc deficient rat.

Three-w-old male Sprague-Dawley rats were given a zinc (Zn)-deficient (0 ppm Zn) or a Zn-adequate diet (30 ppm Zn) supplemented with 0, 0.5 or 100 ppm cadmium (Cd) for up to 5 mo. The proximal convoluted tubules of the kidneys had degenerative changes in the rats fed the Zn-deficient diet containing 100 ppm Cd [Zn 0, Cd 100], but there were no lesions in other groups. Electron microscopy showed cytoplasmic vacuolation of the proximal tubules, mitochondrial swelling and coagulative necrosis in Zn 0:Cd 100 rats. The present study revealed diminished bone growth and cortical thinning of the femur, but there was no osteomalacia seen in Itai-Itai disease patients. The results indicate that Zn deficiency may enhance the renal toxicity of Cd, but that dietary Cd did not cause osteomalacia even under severe Zn-deficient conditions.

Idazoxan decreases estrogen-induced lordosis in female but not "hormone-independent" lordosis in male guinea pigs of an inbred strain.

This experiment examined whether the imidazoline idazoxan (which binds to alpha-noradrenergic receptors and to imidazoline-preferring sites) interferes with hormone-dependent or hormone-independent lordosis responses. Ovariectomized (ovx) Strain 2 female guinea pigs which were sexually receptive after receiving estradiol benzoate (EB; 3 micrograms/d for 3 days) were injected with either idazoxan (10 mg/kg) or with vehicle at 24 hr after the last EB injection. Idazoxan significantly decreased EB-facilitated lordosis responses in these females. Castrated Strain 2 males, which show lordosis behavior without gonadal hormone administration, were injected with the same dosage of idazoxan (10 mg/kg) or with vehicle. Idazoxan did not inhibit lordosis behavior in these males.

Dyspnoea and thoracic spinal deformation in rats after oral prizidilol (SK&F 92657-A2).

Prizidilol (SK&F 92657-A2), an anti-hypertensive agent, has undergone a range of prescribed toxicity studies required for the investigation of possible adverse drug effects. During the second year of the 2-year rat oral study, a variety of symptoms were exhibited by males receiving 1600 mg of the compound day-1kg-1 by gavage. These animals became lethargic, slouched and developed dyspnoea which became progressively more severe during the course of the study. Necropsy of the affected rats revealed severely haemorrhagic lungs, cardiac hypertrophy and lordosis of the spine into the thoracic cavity. At the 2-year terminal kill, a proportion of the male rats receiving 100 and 400 mg of prizidilol day-1kg-1 were identified with similar but less severe spinal deformation. No female was found with spinal changes but all the rats receiving prizidilol showed haemorrhagic lungs and enlarged hearts. The lordosis of the affected males was always confined to the thoracic spine and this, along with the cardiac hypertrophy, presumably led to marked reduction in the volume of the thoracic cavity, inducing the dyspnoea. Thoracic vertebral body damage, possibly a precursor to the spinal deformities, was found in male rats from both drug-treated and control groups. The nature of the spinal lesion is at present under investigation.

The "stright-jacket" syndrome in chicks. II. Mechanism of development.

In a longitudinal study including measurement of the pressure in the amniotic cavity, amniotomy, and planimetric evaluation of the size of the amniotic sac, we investigated the development of the "strait jacket" syndrome in White Leghorn chicken embryos injected intraamniotically (ia) or paraamniotically on the fourth day of incubation with histone or embryotoxic serum, with the following results. Hyperlordosis and eventration developed as an outcome of tonic contraction of the amnion, which was observed only three hours after ia administration. Contraction of the amnion caused elevation of the intraamniotic pressure, which, 12 hours after ia injection, attained a mean value of 22.4 Pa (2.3 mm H2O). This value was not only significantly higher than the mean for control embryos (3.9 Pa), but it was critically close to the mean fluid pressure in the brain vesicles. Loss of the latter overpressure caused the vesicles to collapse, and the walls shriveled and exencephaly developed. Paraamniotic injection was not followed by either contraction of the amnion, or significant increase in intraamniotic pressure. This did not prevent heart malformations and cranioschisis of various extent. The majority of cardiovascular malformations were probably the hemodynamic consequence of overfilling of the intraembryonic vascular bed, which was one of the early signs of the effect question. Cranial-vault defects can be causally associated with the formation of amnionic adhesion and fusion with the epidermal ectoderm. This observation stresses the significance of the embryonic membranes and the fluid pressures within them for the development of certain congenital deformities and concentrates attention on teratological study of substances that induce protracted contraction of smooth muscle.

Action of luteinizing hormone-releasing factor (lrf) in the initiation of lordosis behavior in the estrone-primed ovariectomized female rat.

In order to evaluate the precise role of luteinizing hormone-releasing factor (LRF) in mediating the onset of sexual behavior, the specificity, time-course, and dose-response relationship of LRF-facilitated lordosis behavior were determined. Ovariectomized female rats, pretreated with estrone and LRF, displayed a pattern of lordosis behavior which differed little from that produced by estrone-progesterone. Little if any lordosis behavior was observed in response to LRF alone, estrone alone, or estrone in combination with luteinizing hormone (LH), follicle-stimulating hormone (FSH), or thyrotropin-releasing factor (TRF). Furthermore, LRF-induced lordosis behavior occurred in the absence of the adrenals, thus eliminating adrenal progesterone as a factor in facilitating the appearnce of lordosis behavior. The LRF-facilitated lordosis behavior was seen 2 h after the injection of LRF and was maintained for a total of 8 h. A minimal dose of 150 ng LRF was required to initiate the first consistent appearance of lordosis behavior; the maximum response was obtained with 500 ng. It is thus suggested that LRF is not only responsible for the ovulatory discharge of LH and subsequent ovulation, but may also play a role in the initiation of the onset of mating behavior in the female rat.

PIP: The action of luteinizing hormone-releasing factor (LRF) in the induction of lordosis behavior in ovariectomized rats (OVX) is described. 139 sexually experienced Sprague-Dawley female rats were ovariectomized at 80-100 days of age and behavioral testing was done 2-3 weeks later. At 9-10 months after ovariectomy adrenals were removed from 16 rats. These animals were given free access to isotonic NaCl solution. Female sexual behavior was expressed as the ratio of the number of lordosis responses to the number of mounts by the male rat. Ovarian hormones (estrone, E; theelin in oil 1 mg/ml) and progesterone (P; lipolutin in oil 50 mg/ml) were used. The pituitary hormones luteinizing hormone (LH) and follicle stimulating hormone (FSH) and releasing factors LRF and TRF were dissolved in physiological saline. All hormones were injected sc. In Experiment 1 to determine the specificity of LRF-induced lordosis responses 16 rats were tested under 8 conditions. Each rat was pretreated with either .25 ng E or 500 ng LRF. Tests for sexual receptivity were conducted 50 hours after E injections. After repeating these tests, adrenal removals (ADX) were done. After 5 days, the E-primed OVX-ADX animals were tested for sexual receptivity 50 hours following an injection of LRF (48 hours after E). In Experiment 2, to determine the time course for the initial appearance of lordosis and the total period of receptivity induced, 24 E-primed OVX rats were tested throughout and 8-hour period following the LRF injections. Each animal was primed with E at zero hour and given LRF at 48 hours. 49 hours after E injections tests were begun and continued at hourly intervals. This sequence was repeated at least 4 times. In Experiment 3, to determine the dose of LRF needed, 99 E-primed OVX rats were injected with doses ranging from 50 to 4000 ng LRF at 48 hours after E injections. Sexual receptivity tests were done 2 hours later. Results showed that sexual behavior in the female rat is dependent on the ovarian hormones estrogen and progesterone. Synthetic LRF exerted a facilitatory effect on the lordosis response. The LRF-facilitatory behavior was shown to be specific but LRF alone did not lead to mating behavior in OVX females. E-priming was a necessary condition to obtain a hgih level of copulatory behavior. The LRF-induced lordosis pattern was independent of adrenal progesterone and apparently not mediated by pituitary hormones. The time lag between LFR injection and induction of sexual behavior suggests that this is not a simple monosynaptic mechanism but may involve intermediate steps such as the activation of protein synthesis in the postsynaptic neurons of the mating center.