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PubMed1986

Accessory olfactory bulb lesions and lordosis behavior in the male rat feminized with ovarian hormones.

Orchidectomized rats were given estrogen and progesterone and tested for feminine behavior in the presence of a mounting male after accessory olfactory bulb removal (AOBR). Complete AOBR caused a rise in the number of estrogen-progesterone-treated male rats responding by lordosis behavior to male mounts as compared to controls and sham-operated animals. By contrast, LQ scores did not appear to differ in these three groups of animals. The results are discussed in terms of involvement of the main and the accessory olfactory systems in the regulation of feminine behavior in the male rat.

Animals↗
PubMed1989

Temporal actions of 16 alpha-hydroxyestrone in the rat: comparisons of lordosis dynamics with other estrogen metabolites and between sexes.

16 alpha-Hydroxyesterone (16OHE1), a metabolite of estradiol (E2) and precursor of estriol (E3), binds to the estrogen receptor (ER) with low affinity (3% of E2), but is estrogenic in both in vitro and in vivo systems. This metabolite is able to bind in a non-dissociable manner to the ER. We examined these properties in vivo by assessing the temporal dynamics of estrogen metabolite action in the rat brain, using lordosis score (LS) to manual stimulation as a serial bioassay of estrogen effect. Male and female castrate Fisher rats were implanted with osmotic minipumps containing either vehicle, E2, 16OHE1, or E3. 16OHE1-induced LS was delayed in onset in both sexes relative to E2 and E3. Male LS reached a similar plateau for all metabolites, whereas female LS reached an initial LS plateau similar in amplitude to the male plateau. Over the next several days, female LS increased to reach a secondary plateau of higher amplitude, which persisted until pump removal. Upon pump removal, E2- and E3-stimulated LS fell to baseline quickly in both sexes, whereas 16OHE1-stimulated LS in males demonstrated a prolongation of maximal LS for 6 days following pump removal. These results suggest that 16OHE1 is estrogenic in the brains of both sexes. The delay of onset of LS with 16OHE1 is consistent with its poor ER affinity. Females were able to augment LS with prolonged exposure to all metabolites, while males could not. The ability of 16OHE1 to maintain maximal LS in the male long after its withdrawal is consistent with its ability to bind non-dissociably to the ER and promote prolonged estrogenic activation. However, females do not exhibit this response, suggesting a sex specificity in the dynamics of ligand-receptor action in the rat brain.

Animals↗
PubMed1986

Hypothalamic nuclear estrogen receptors and lordosis behavior in hamsters.

These experiments examined the effects of a high and a low dose of estradiol benzoate (EB) in enhancing lordosis behavior and correlated these effects with the retention of hypothalamic nuclear estrogen receptors (NER) in female hamsters. Ten micrograms EB was significantly more effective in facilitating sexual receptivity in hamsters when it was followed 36 or 48 hr later by 0.5 mg progesterone (P), but not when P was given 24 hr after EB. Low levels of behavioral responses were observed in animals that received P at 24, 36 or 48 hr after 2 micrograms EB. Correspondingly, although the hypothalamic NER levels were equally elevated 24 hr after either a low or a high dose of EB, these receptor concentrations remained high at 36 and 48 hr post EB, only in those animals that received the high estrogen dose. The results of these experiments suggest that the long-term retention of NERs (which is maintained by a single high EB dose) may play an important role in the enhancement of sexual receptivity in hamsters.

Animals↗
PubMed1987

Photoperiodic modulation of steroid-induced lordosis in golden hamsters.

The photoperiodic modulation of steroid-induced receptive behavior was investigated using ovariectomized female hamsters (Mesocricetus auratus) kept in short (6 hr of light/day) or long (16 hr of light/day) photoperiods. When a low dose of estradiol (E) was used, a significantly larger percentage of animals housed in long days displayed lordosis behavior than did animals housed in short days in tests with intact males as stimuli. This effect of photoperiod was reduced when a high dose of E was employed and was absent when E treatment was supplemented with progesterone. These observations suggest that a reduction in behavioral sensitivity to E may contribute to the reproductive quiescence induced by short photoperiods.

Aggression↗
PubMed1996

Lordosis-inhibiting effect of progesterone in female rats with lesions in septum, preoptic area, or dorsal raphe nucleus.

Radiofrequency lesions in the septum (SL), the preoptic area (POAL), or the dorsal raphe nucleus (DRL) were made in ovariectomized rats. In a control group of 16 females, ovariectomy, but no brain surgery, was performed. All animals except half of the control rats received injections of 5 mg progesterone (P) 1 h prior to the injection of 5 micrograms/kg b.w. of estradiol benzoate (EB). Instead of 5 mg P, oil was administered to half of the controls. Forty-four hours after EB, all females received 0.5 mg P. A sexual behavior test was performed 4 h after the last injection of P. The result was that oil-treated control rats showed high lordosis quotient (LQ) and soliciting behavior. In contrast, low scores of LQ and no soliciting behavior were observed in all of the 5 mg P-treated rats, even if the SL, POAL, or DRL was made. These results suggest that the septum, the preoptic area, and the dorsal raphe nucleus are not essential for the female sexual behavior-inhibiting mechanisms of progesterone.

Animals↗
PubMedDate not supplied

Alpha-methyltyptamine blocks facilitation of lordosis by progesterone in spayed, extrogen-primed rats.

Alpha-methyltryptamine, a drug which stimulates serotonergic receptors in the central nervous system, inhibited the induction of sexual receptivity in spayed female rats by estradiol benzoate and progesterone. The drug had no effect on the sexual receptivity induced by estradiol benzoate alone. These data are consistent with the hypothesis that progesterone facilitates lordosis in estrogen-primed rats by inhibiting a serotonergic system in the brain. The data also suggest that estradiol and progesterone act on separate neurochemical systems to induce estrous behavior in rats.

Animals↗
PubMed1977

Role of catechol estrogens in activation of lordosis in female rats and guinea pigs.

In a variety of experiments, we tested the effectiveness of the 2-hydroxylated estrogen in facilitating sexual receptivity. A single injection of 2-hydroxy-estradiol-17beta (2-OHE2) to ovariectomized rats or 2-hydroxy-estrone (2-OHE1) to ovariectomized guinea pigs was ineffective in priming animals for facilitation of sexual receptivity even when a subsequent injection of progesterone was administered. The only facilitatory effect of catechol estrogens on lordosis that was demonstrated in this study occurred when 2-OHE2 was injected in combination with E2 and a subsequent injection of progesterone was given to rats. These results suggest a cooperatively between catechol estrogen and E2, but they also indicate that catechol estrogens, by themselves, do not play a crucial role in mediating sexual receptivity in rodents.

Animals↗
PubMed1988

Inhibitory action of alpha-melanocyte stimulating hormone on lordosis in rats: possible involvement of serotonin.

Alpha-melanocyte stimulating hormone (MSH) has been found to exert a short- and a long-term inhibitory action on lordosis. The present series of experiments examined the possibility that these effects are mediated by MSH-induced alterations in activity at serotonin type II receptors. In Experiment 1, quipazine (serotonin type II agonist) was found to significantly attenuate the short-term effect of MSH while only partially attenuating the long-term action of MSH. In the second experiment, doses of MSH and of pirenperone (serotonin type II antagonist) that did not inhibit lordotic responding when administered alone were found to inhibit responding when administered together. It was also found that 20 ng MSH produced a long-term, but not a short-term inhibition of receptivity. The results of Experiment 3 indicated that the inhibition observed in Experiment 2 could be reversed by quipazine. These results suggest that alterations in serotonin activity are one mechanism by which the effects of MSH are produced. The relevance of this to the regulation of reproductive states is discussed.

Animals↗
PubMed1987

Relationship between lordosis and the position of the centre of reaction of the spinal disc.

Whenever we stand upright in apparent static equilibrium, we are, in fact, continuously making minor adjustments in order to maintain our balance. For each intervertebral joint, a point must exist at which all moments applied to the joint are continually and dynamically balanced. This point, known as the centre of reaction, is a mathematical invention necessary to perform analyses of spinal motion, but which need not be associated with any real anatomical structure. As the spine flexes and extends, this centre is expected to move; where it moves and the rationale for its motion is worthy of enquiry. In this paper, we propose that the centre of reaction remains confined to the nucleus of the disc, but only if one simple but crucial assumption is made; that the motion of the spine and control of its musculature maintain a minimum and equal stress at each intervertebral joint. This is a simple hypothesis which imposes a very specific relationship between lordosis and the centre of reaction. We investigate this relationship and its consequences on the teaching of lifting. The impossibility of designing experiments adequately to verify this hypothesis prevents in vivo verification, and, therefore, the model's verification must be made through the inferred consequences. For example, the capability of correctly predicting physiological responses of the musculoskeletal system is an indication of the validity of a model; however, this is not universally accepted. In this particular case, additional experimental data are available in the form of the locus of the centre of rotation of a vertebra vis-à-vis its lower neighbour as the spine flexes and extends. It is instructive to compare the predicted locus of the centre of reaction to experimentally determined locus of the centre of rotation; more than just coincidental similarities are found.

Biomechanical Phenomena↗
PubMed1985

Oxytocin stimulates lordosis behavior in female rats.

Oxytocin, either intraperitoneally injected (200 ng/rat) or intracerebroventricularly infused (1 ng/rat in 4 microliters saline) 60 and 15 min respectively before testing, significantly increased the lordosis response to the mounting male of ovariectomized, estrogen/progesterone treated rats. The intracerebroventricular infusion of oxytocin 0.1 ng/rat had no effect; nor did saline. These results indicate that oxytocin increases female receptivity, the site of action probably being in the central nervous system.

Animals↗
PubMed1993

Antisense oligonucleotide blocks progesterone-induced lordosis behavior in ovariectomized rats.

Antisense oligonucleotides were utilized to interfere with the synthesis of progesterone receptor. A specific aODN was shown to decrease significantly the levels of PR in the T47D cell line known to express the PR gene. The molecule described was proved to be effective in hindering the effect of progesterone on target gene expression in T47D cells. The aODN was then utilized in an in vivo study to test its efficacy on the female rat sex behavior. Its injection in the ventromedial hypothalamus significantly inhibited the estrous responsiveness induced by progesterone. This study provides a clear demonstration of the full involvement of PR in the manifestation of lordosis behavior and demonstrates the activity of an aODN as antiprogestative.

Animals↗
PubMed1981

Persistence of dihydrotestosterone inhibition of lordosis in estrogen-primed rats fed a tryptophan-deficient diet.

Administering increasing dosages of 5alpha-dihydrotestosterone propionate (DHTP) (0, 40, or 80 microgram/100 g in oil daily) to ovariectomized female rats treated concurrently with estradiol benzoate (EB) (1 microgram/100 g in oil daily) caused significant, equivalent reduction in lordotic responsiveness in rats maintained either on a tryptophan-deficient corn diet or on a corn diet to which L-tryptophan was added. Whole brain concentrations of 5-hydroxytryptamine (5-HT) and of 5-hydroxyindoleacetic acid were approximately two times higher in rats fed corn+tryptophan versus corn alone. These findings suggest that the ability of DHTP to inhibit lordosis probably depends upon some mechanism other than a facilitation of 5HT release from serotonergic neurons.

Animals↗
PubMed2006

Stepwise reduction of functional spinal structures increase range of motion and change lordosis angle.

Many investigators have performed studies on specific defect situations or determined the contribution on isolated structures. Investigating the contribution of functional structures requires obtaining the kinematic response directly on spinal segments. The purpose of this study was to quantify the function of anatomical components on lumbar segments for different loading magnitudes. Eight spinal segments (L4-5) with a median age of 52 years (ranging from 38 to 59 years) and a low degree of disc degeneration were utilized for the in vitro testing. Specimens were mounted in a custom-built spine tester and loaded with pure moments (1-10 N m) to move within three anatomical planes at a loading rate of 1.0 degrees /s. Anatomy was successively reduced by: ligaments, facet capsules, joints and nucleus. Data were evaluated for range of motion, neutral zone and lordosis angle. Transection of posterior ligaments predominantly increased specimen flexion for all bending moments applied. Supraspinous ligament also indicated to resist in extension slightly, whereas the facet capsules did not. Facet joints contributed to axial rotation, but not in lateral bending. The anterior longitudinal ligament was found to slightly resist in axial rotation, but strongly in extension. Nucleotomy caused largest increase of all movements. The unloaded posture of the specimens changed after ligament dissection, indicating ligament pretension. The region of lumbar spine is interesting for finite element (FE) simulation due to the high evidence of disc degeneration and injuries. This study may help to understand the function of specific anatomical structures and assists in FE model calibration. We suggest to start a calibration procedure for such models with the smallest functional structure (annulus) and to cumulatively add further structures.

Adult↗
PubMed1996

NADPH diaphorase activity and nitric oxide synthase immunoreactivity in lordosis-relevant neurons of the ventromedial hypothalamus.

The distribution of the enzymes NADPH diaphorase and nitric oxide synthase in the ventromedial nucleus of the hypothalamus of cycling and ovariectomized/estrogen-treated and control female rats was demonstrated using histochemical and immunocytochemical methods. Serial section analysis of vibratome sections through the entire ventromedial nucleus showed that NADPH diaphorase cellular staining was localized primarily in the ventrolateral subdivision. NADPH diaphorase staining was visible in both neuronal perikarya and processes. Light microscopic immunocytochemistry using affinity-purified polyclonal antibodies to brain nitric oxide synthase revealed a similar pattern of labelling within the ventromedial nucleus and within neurons of the ventrolateral subdivision of the ventromedial nucleus. Control experiments involved omitting the primary antibodies; no labelling was visible under these conditions. Some, but not all, neurons in the ventrolateral subdivision of the ventromedial nucleus contained both NADPH diaphorase and brain nitric oxide synthase as demonstrated by co-localization of these two enzymes in individual cells of this area. That NADPH diaphorase and brain nitric oxide synthase were found in estrogen-binding cells was shown by co-localization of NADPH diaphorase and estrogen receptor and brain nitric oxide synthase and estrogen receptor at the light and ultrastructural levels, respectively. Our studies suggest that brain nitric oxide synthase is present and may be subject to estrogenic influences in lordosis-relevant neurons in the ventrolateral subdivision of the ventromedial nucleus. The hypothalamus is a primary subcortical regulatory center controlling sympathetic function. Therefore, not only is nitric oxide likely to be important for reproductive behavior, but also for the regulation of responses to emotional stress and other autonomic functions.

Animals↗
PubMed1998

Regulation of neuronal nitric oxide synthase mRNA in lordosis-relevant neurons of the ventromedial hypothalamus following short-term estrogen treatment.

Short-term estrogenic regulation of neuronal nitric oxide synthase (nNOS) mRNA in the ventrolateral subdivision of the ventromedial nucleus (VLVMN), an area central to lordosis, was demonstrated using in situ hybridization. Estrogen-treated animals showed a significantly greater signal in the VLVMN, but not the arcuate or supraoptic nuclei, compared to ovariectomized controls. Neuronal NOS may be involved in early actions of estrogen in the VLVMN.

Animals↗
PubMed1998

Functions of the caudal periaqueductal gray in lactating rats: kyphosis, lordosis, maternal aggression, and fearfulness.

Severe impairment of the kyphotic nursing posture in lactating rats found previously after prepartum lesions of the caudal intercollicular periaqueductal gray (cPAG-x) was confirmed and was extended to a continuous 24-hr period. Litters of cPAG-x dams gained approximately 10% less weight postnatally than controls, which was in part related to their dams' compensatory prone nursing posture that was ineffective for milk letdown. Sexual proceptivity and receptivity (lordosis) during the postpartum estrus were virtually eliminated in subjects with relatively large bilateral cPAG lesions. The doubling of maternal attacks toward a male intruder after lesioning was also confirmed and was related to reduced fearfulness in an elevated plus-maze. Thus, the cPAG plays a multifaceted role in parturient rats; it is involved in the mediation of nursing, sexual, aggressive, and fear behaviors.

Aggression↗
PubMed1992

The effect of Luque-rod instrumentation on the sagittal contour of the lumbosacral spine in adolescent idiopathic scoliosis and the preservation of a physiologic lumbar lordosis.

The changes in the sagittal alignment of the lumbar spine were investigated in 28 patients with adolescent idiopathic scoliosis undergoing long posterior spinal fusion to L4 or L5 with contoured Luque rods and segmental sublaminar wiring. The lumbar lordosis over the instrumented levels was preserved, and there was no compensatory hyperlordosis of vertebral segments distal to the fusion. In situations where long posterior spinal fusions are indicated, instrumentation with contoured Luque rods and segmental sublaminar wiring can preserve the normal sagittal alignment of the lumbosacral spine.

Adolescent↗
PubMed2005

Anterior correction of cervical spine lordosis using an adjustable depth tap: technical note.

OBJECTIVE: In cases of multilevel anterior cervical spine decompression where intervening vertebral bodies need to be incorporated into the anterior plate construct, it may be difficult to apply the plate flush against the entire anterior cortical surface of the spine segment. Some have suggested using the levering property of bicortical screws to "pull" the body against the plate. Others have recommended contouring the anterior cervical plate with a plate bender. The objective of this work was to describe a novel technique using the adjustable depth tap provided in the Atlantis plating system for achieving cervical spine alignment against the lordotic plate after multilevel anterior decompression. METHODS: We describe an illustrative case of a 14-year-old girl with complex cervical spine fractures after trauma. We used the 4.0-mm adjustable depth tap in the Atlantis plating system to lever the C4 body against the premachined lordotic plate. RESULTS: Cervical lordosis and anterior cervical plate placement were accomplished after multilevel anterior cervical decompression with the use of an adjustable depth tap. CONCLUSIONS: Bicortical screw placement and plate bending have drawbacks in trying to apply the anterior cervical plate firmly to the anterior surface of the cervical spine. We describe a new and safe technique of using an adjustable depth tap for achieving that same goal without any obvious drawbacks.

Adolescent↗