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PubMed1995

-Fos expression in female hamster brain following sexual and aggressive behaviors.

The goal of these experiments was to use c-Fos immunocytochemistry to determine areas of the female hamster brain that are active during lordosis and aggression. Ovariectomized hamsters were given (i) estradiol and progesterone, plus a lordosis test, (ii) estradiol and progesterone, but no lordosis test, (iii) oil, plus an aggressive behavior test, or (iv) oil, but no behavior test. Results showed that following lordosis, there was increased c-Fos expression in the medial bed nucleus of the stria terminalis, medial accumbens, medial preoptic nucleus, paraventricular nucleus and medial amygdala. Following a single aggression test, c-Fos was significantly increased only within the medial amygdala. There was no effect of lordosis or aggression on c-Fos expression within the lateral or central ventromedial hypothalamus, suprachiasmatic nucleus or dorsal midbrain central gray. In a second experiment, ovariectomized female hamsters were given (i) repeated aggressive experience, (ii) a single aggression test or (iii) no aggression test. Because some females were not aggressive towards males, they became a separate group post hoc. The number of cells expressing c-Fos was higher in the medial preoptic nucleus and medial amygdala of females given a single aggressive test and in non-aggressive females vs control females. Females given prior aggressive experience showed higher c-Fos expression only in the medial preoptic nucleus. These results demonstrate that increased neural activation in several forebrain nuclei is seen after sexual or aggressive behaviors in female hamsters. However, because the pattern of c-Fos staining in the non-aggressive females was similar to the pattern in aggressive females, this questions previous conclusions regarding the behavioral specificity of these effects and suggests instead that such activation is common to social interactions in general.

Aggression↗
PubMed1984

RNA and protein synthesis inhibitors: effects on sexual behavior in female rats.

Biochemical evidence indicates that many steroid hormone effects on target tissues are mediated via actions on the genome. Studies on the hormonal control of reproductive behavior have demonstrated several effects of RNA or protein synthesis inhibitors on female sexual behavior in rats. In female rats treated with estrogen and progesterone, intracranial application of actinomycin-D (an RNA synthesis inhibitor) can disrupt lordosis responding if the drug is given in conjunction with estrogen, but not with progesterone. Protein synthesis inhibitors (cycloheximide or anisomycin) applied intracranially at the time of estrogen also disrupt lordosis, with anisomycin antagonizing the progesterone-facilitation of lordosis. Possible neural sites of action of these drugs are considered, as are alternative modes of action of these synthesis inhibitors. Whereas the effects of estrogen on lordosis include the synthesis of some, as yet unidentified, proteins, the exact role for protein synthesis in the mediation of progesterone's actions on lordosis remains less certain.

Animals↗
PubMed1987

Lesions in the preoptic area suppressed sexual receptivity in ovariectomized rats with estrogen implants in the ventromedial hypothalamus.

The objective of the experiment was to determine if electrolytic ablation of a portion of the preoptic area (POA) influenced the activation of female lordosis behavior by implants of estradiol benzoate in the ventromedial hypothalamus (VMH) of ovariectomized (OVX) rats. Two weeks after ovariectomy, rats received either bilateral electrolytic lesions (2 mA for 10 sec in Experiment 1, or 1 mA for 5 sec in Experiment 2) in the POA, or sham lesions (all procedures except passage of current). On the same day (day 0 of the experiment) thirty-gauge stainless steel cannulae containing crystalline estradiol benzoate were stereotaxically placed bilaterally into the VMH of all the rats. Subsequently, females were tested for the lordosis response to stud males on days 2, 4, 6, 8, and 10 in Experiment 1 or on days 7, 14 and 15 in Experiment 2. All rats received 0.5 mg progesterone (SC) only before the last test. A female was considered sexually receptive if she exhibited a lordosis quotient (LQ) greater than or equal to 10 (LQ = No. lordosis responses/10 mounts by male X 100). The frequencies for sexual receptivity in females with POA lesions were significantly lower than those for control females without lesions in both experiments. Additionally the degree of receptivity (lordosis quotient) was significantly lower on each test day for rats with POA lesions than that for rats without POA lesions. The results imply that the maintenance of the integrity of the POA under this experimental condition was important for the expression of the facilitative influence of the VMH on lordotic responsiveness.

Animals↗
PubMed2004

Evidence that the effect of melanocortins on female sexual behavior in preoptic area is mediated by the MC3 receptor; Participation of nitric oxide.

alpha-MSH is involved in reproductive processes and can regulate the expression of lordosis, an important component of female reproductive behavior in rats and many other species. In this study, we investigated the effects of MSH peptides on lordosis behavior when injected in medial preoptic area (POA) of ovariectomised rats primed with estradiol. The results show an increase in lordotic activity after bilateral administration of alpha-MSH and gamma-MSH. Interestingly, the treatment with the MC4 receptor antagonist HS014 did not block the stimulatory effect of alpha-MSH. Moreover, the injection of HS014 did not itself modify the lordosis quotient. Nitric oxide has been suggested to play a crucial role in the regulation of lordosis behavior via stimulation of guanylyl cyclase to synthesize cGMP. In order to determine the participation of NO in the effect of the melanocortins, another group of rats were treated with L-NAME, an inhibitor of NOS, alone or 15 min before the injection of alpha-MSH or gamma-MSH. The injection of L-NAME into the POA of E-primed rats 15 min before the test for sexual receptivity did not modify significantly the lordosis quotient at the two doses examined. The treatment with L-NAME at the lowest dose completely abolished the stimulatory effect of alpha-MSH and gamma-MSH on sexual behavior. The results indicate that the effects of MSH peptides on female sexual behavior in this area are mediated through specific MC receptor, that could be the MC3 receptor and that NO mediates the melanocortins effects.

Animals↗
PubMed2004

GABAA-5-HT1A receptor interaction in the mediobasal hypothalamus.

Both serotonin (5-HT) and gamma-aminobutyric acid (GABA) modulate female rat lordosis behavior and appear to interact in their control of the behavior. The current experiments were designed to investigate the interaction between these two neurotransmitters in sexually receptive female rats. Ovariectomized female rats, with bilateral cannulae directed toward the ventromedial nucleus of the hypothalamus (VMN), were hormonally primed with 10 microg estradiol benzoate and 500 microg progesterone. Sexual behavior was examined after intracranial infusion with 200 ng (+/-)-8-hydroxy 2-(di-n-propylamino)tetralin (8-OH-DPAT), 25 ng (5-aminomethyl-3-hydroxyisoxazole)hydrobromide (muscimol), 10 ng bicuculline or a combination of the drugs. As expected, 8-OH-DPAT reduced lordosis behavior and muscimol attenuated this inhibition in a bicuculline-sensitive manner. Muscimol alone also reduced lordosis behavior. These findings contrast with several reports that muscimol facilitates lordosis behavior of suboptimally hormonally primed female rats. The current outcome is discussed in terms of procedural differences between the present experiment and earlier studies. It is suggested that muscimol may enhance lordosis responding in suboptimally hormonally primed rats by activation of GABAA receptors located dorsal to the VMN. In contrast, activation of receptors located more ventrally within the mediobasal hypothalamus (MBH) may inhibit the behavior of rats that are already sexually receptive.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2006

Role of glutamate receptors in the ventromedial hypothalamus in the regulation of female rat sexual behaviors I. Behavioral effects of glutamate and its selective receptor agonists AMPA, NMDA and kainate.

Bilateral infusions of glutamate or kainate to the ventromedial hypothalamus (VMH) have been shown previously to produce a rapid inhibition of lordosis in estrogen-primed female rats induced by manual flank stimulation. The present study examined whether glutamate or selective ionotrophic glutamate receptor agonists can disrupt appetitive and consummatory sexual behaviors following bilateral infusions to the VMH of females during copulation with male rats. Ovariectomized, sexually experienced female rats were implanted bilaterally with guide cannulae aimed at the ventrolateral VMH. After recovery from surgery, females were primed with estradiol benzoate and progesterone and infused with different doses of glutamate, AMPA, NMDA or kainate (n=9-10 in each dose group) 3 min prior to a test with sexually vigorous males in bilevel chambers. Glutamate infusions decreased the display of hops and darts and produced a trend toward decreased lordosis. AMPA infusions decreased the display of solicitations, hops and darts, and lordosis. NMDA infusions decreased lordosis and increased defensive behaviors and pacing. Kainate infusions decreased solicitations, hops and darts, and lordosis, and increased defensive behaviors and pacing. These data indicate that the activation of glutamate receptors in the VMH is inhibitory for both appetitive and consummatory aspects of sexual behavior in the female rat.

Animals↗
PubMedDate not supplied

Posterior lumbar interbody fusion for lytic spondylolisthesis: restoration of sagittal balance using insert-and-rotate interbody spacers.

BACKGROUND CONTEXT: The role of surgical correction of sagittal plane deformity in cases of lytic spondylolisthesis remains controversial. While some early evidence is emerging of the possible short- and long-term benefits of restoring spinal balance, many surgeons have been concerned about the associated risks. The insert-and-rotate posterior lumbar interbody fusion (PLIF) technique, first described by Jaslow in 1946, may enable surgeons to safely and effectively correct sagittal balance through a single posterior approach. PURPOSE: To determine whether the focal kyphosis and subluxation associated with a lytic lumbosacral spondylolisthesis can be safely and effectively corrected using a single-stage posterior distraction/reduction technique and insert-and-rotate interbody fusion spacers. STUDY DESIGN/SETTING: A prospective, single cohort, observational study of the clinical outcomes and retrospective radiological review, in a series of 18 consecutive patients with lytic spondylolisthesis Grades I to IV, operated between September 2000 and December 2002. PATIENT SAMPLE: Mean age of 50.2 years (range, 15.5 to 77.8 years). Principal indication for surgery was relief of radicular pain secondary to foraminal stenosis in 16 of 18 patients, and back pain was the principal symptom in 2 patients. Mean preoperative slip was 30.2% (range, 9% to 78%). Mean preoperative focal lordosis was 10.6 degrees (range, -12 to 33 degrees). OUTCOME MEASURES: Minimum 12-month follow-up was available on all patients except one, who died of unrelated causes after his 6-month visit. Patients completed Visual Analogue Pain Score (VAS), Low Back Outcome Score (LBOS), Short Form (SF)-12 and patient satisfaction questionnaires. Pre- and postoperative measurements of the percentage slip and lumbar lordosis of the involved segments were available on 13 patients. SURGICAL METHODS: Decompressive laminectomy was followed by reduction of the spondylolisthesis with the aid of intervertebral disc space spreaders and supplementary pedicle screw instrumentation. The vertebral bodies were supported with bilateral intervertebral lordotic spacers made from carbon fiber, titanium mesh or polyether-ether-ketone (Medtronic Sofamor Danek, Memphis, TN). These were inserted on their sides and rotated 90 degrees before placing bone graft to either side of them, within the disc space. RESULTS: Mean follow-up was 17.3 months. Mean preoperative measures of VAS and LBOS of 5.0+/-2.3 and 29.3+/-16.4, respectively, improved to 2.9+/-3.0 (p=.01) and 42.6+/-20.1 (p=.005) at last follow-up. Fifteen of 18 patients (83.3%) considered their outcome to be good or excellent. Mean preoperative slip reduced from 30.2% to 6.2% (p=.001). Mean focal lordosis improved from 10.6 to 18.1 degrees (p=.02). Lumbar lordosis (L1-S1) did not change, but the lordosis of the lumbar segments above the fusion reduced from 46.8 to 34.9 degrees (p=.02). There were no serious implant or procedural complications. Postoperatively, there was a delayed and temporary weakness of ankle dorsiflexion in a patient with Grade IV spondylolisthesis. CONCLUSIONS: This series suggests that PLIF using an insert-and-rotate technique can yield satisfactory clinical outcomes and substantial deformity correction using a posterior only approach and with low levels of serious or permanent complications. Longer-term clinical outcome and comparative studies are required regarding the importance of the restoration of spinal balance.

Adolescent↗
PubMed2004

The nitric oxide pathway participates in estrous behavior induced by progesterone and some of its ring A-reduced metabolites.

Intracerebral and intravenous administration of progesterone (P) and its ring A-reduced metabolites induces intense sexual behavior (lordosis and proceptivity) in estrogen-primed rats. The present study tested the hypothesis that the nitric oxide-cGMP-protein kinase G pathway is involved in the facilitation of sexual behavior induced by the intracerebroventricular (i.c.v.) administration of P (130 ng) and its ring A-reduced metabolites 5alpha-dihydroprogesterone (5alpha-DHP; 13 ng) and 5alpha,3alpha-pregnanolone (5alpha,3alpha-Pgl; 13 ng). In Experiment 1, we tested the relevance of the nitric oxide/cGMP pathway by infusing a nitric oxide synthase inhibitor or a nitric oxide-dependent, soluble guanylyl cyclase inhibitor icv before progestin administration. The lordosis induced by P, 5alpha-DHP and 5alpha,3alpha-Pgl was significantly reduced at 2 h after progestin infusion by the previous injection of either a nitric oxide synthase inhibitor or by a soluble guanylyl cyclase inhibitor. Lordosis behavior returned to control values by 4 h. In Experiment 2, i.c.v. infusion of the protein kinase G inhibitor KT5823 significantly inhibited the lordosis behavior induced by all three progestins at 2 h. These data support the hypothesis that the nitric oxide/cGMP/protein kinase G pathway is involved in the lordosis induced by P and some of its ring A-reduced metabolites.

5-alpha-Dihydroprogesterone↗
PubMed1998

Functional integration among 5-hydroxytryptamine receptor families in the control of female rat sexual behavior.

Serotonin (5-HT) receptor interaction in the control of female rat lordosis behavior was examined. Ovariectomized rats, with bilateral implants in the ventromedial nucleus of the hypothalamus (VMN), were hormonally primed with 25 micrograms estradiol benzoate and 500 micrograms progesterone. Rats were infused with the 5-HT3 receptor antagonist, 3-tropanyl-indole-3 carbonylate (tropisetron; 500 ng), or were coinfused with the 5-HT3 receptor antagonist and the 5-HT2A/2C receptor agonist, 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI; 500, 1500, or 2000 ng). Additional ovariectomized, hormone-primed rats received bilateral VMN infusions with the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT; 200 ng), or were coinfused with the 5-HT1A receptor agonist and the 5-HT3 receptor agonist, m-chlorophenyl-biguanide (mCPBG; 250, 500, or 1000 ng). Lordosis behavior was observed prior to VMN infusion, during the infusion and for 30 consecutive minutes thereafter. Tropisetron reduced the lordosis to mount (L/M) ratio in every animal investigated but the decline was attenuated by coinfusion with DOI. Similarly, the L/M ratio declined following infusion with 8-OH-DPAT and the decline was dose-dependently reduced by coinfusion with mCPBG. Only the 5-HT3 receptor agonist altered the quality of the lordosis reflex. These studies provide evidence that the effects of 5-HT on female rat lordosis behavior involve the integrated activity of at least 3 different 5-HT receptor families.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2002

Strain differences in the response to the 5-HT1A receptor agonist, 8-OH-DPAT.

Fischer and Sprague-Dawley ovariectomized rats were hormonally primed with estradiol benzoate (EB) and progesterone, and the ability of the 5-HT(1A) receptor agonist, (+/-) 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), to inhibit lordosis behavior was examined. Both strains showed rapid inhibition of lordosis behavior following either intraperitoneal or subcutaneous treatment with 8-OH-DPAT. Similarly, in both strains, pretreatment with EB (1 week prior to estrogen and progesterone priming) attenuated the lordosis-inhibiting effects of 8-OH-DPAT. However, Sprague-Dawley females showed a greater decline in lordosis behavior with a lower dose of 8-OH-DPAT than did Fischer females. The strain difference was present in females that had been preprimed with EB as well as in females receiving a single estrogen and progesterone priming. Moreover, strain differences were present across different priming doses of EB. Sprague-Dawley females were also more likely to show flat body posture after injection with 8-OH-DPAT so that the greater sensitivity of this strain to the 5-HT(1A) receptor agonist was not restricted to the drug's effect on lordosis behavior. These findings lead to the suggestion that, relative to Fischer rats, Sprague-Dawley females are more responsive to the 5-HT(1A) receptor agonist. Possible explanations for this strain difference are discussed.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2002

GABA(A) receptor regulation of kyphotic nursing and female sexual behavior in the caudal ventrolateral periaqueductal gray of postpartum rats.

Bilateral lesions of the ventrolateral caudal periaqueductal gray inhibit lordosis and kyphosis, the postures of female sexual receptivity and maternal nursing that are characterized respectively by dorsoflexion and ventroflexion of the spinal column. These lesions also inhibit the solicitation behaviors that accompany lordosis, but they do not impair retrieval or licking of pups. We tested the hypothesis that reproductive behaviors affected by these lesions are tonically inhibited by activity of the GABA(A) receptor via site-specific manipulations of receptor activity. Rats were bilaterally implanted during pregnancy with guide cannulae aimed at the caudal periaqueductal gray and ovariectomized on day 1 postpartum. Microinfusions (0.25 microl/side) of saline or drug took place on days 5 and 7 postpartum into the dorsolateral column and on days 9 and 11 into the ventrolateral column. Five minutes post-infusion dams were reunited with their pups and their maternal behavior was observed for 30 min. Feminine sexual behaviors were evaluated post-weaning after another set of microinfusions in the ventrolateral caudal periaqueductal gray. Potential facilitation of kyphosis and lordosis was tested with the GABA(A) antagonist bicuculline (15 ng/side) during sub-threshold conditions, i.e., non-suckling pups or sub-threshold ovarian hormone dosages; potential inhibition of these postures was tested with the GABA(A) agonist muscimol (125 ng/side) during optimal conditions, i.e., suckling pups or supra-threshold ovarian hormone treatments. Dorsolateral drug manipulations were ineffective. In the ventrolateral periaqueductal gray bicuculline significantly increased and muscimol significantly decreased kyphosis, lordosis, and sexual solicitations compared with saline. Retrieval and licking of pups were not altered by GABA(A) manipulations. These findings suggest that the reproductive postures of female rats, lordosis and kyphosis, as well as sexual solicitations, are tonically inhibited by the neurotransmitter GABA within the ventrolateral caudal periaqueductal gray in the midbrain. In contrast, retrieval and licking of pups appear to be under separate neurochemical or neuroanatomical control, or both. Further, this tonic inhibition is likely relieved by excitatory somatosensory inputs to this site, from mounting and suckling respectively.

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↗
PubMed2000

Estrogens, brain and behavior: studies in fundamental neurobiology and observations related to women's health.

Mechanisms and consequences of the effects of estrogen on the brain have been studied both at the fundamental level and with therapeutic applications in mind. Estrogenic hormones binding in particular neurons in a limbic-hypothalamic system and their effects on the electrophysiology and molecular biology of medial hypothalamic neurons were central in establishing the first circuit for a mammalian behavior, the female-typical mating behavior, lordosis. Notably, the ability of estradiol to facilitate transcription from six genes whose products are important for lordosis behavior proved that hormones can turn on genes in specific neurons at specific times, with sensible behavioral consequences. The use of a gene knockout for estrogen receptor alpha (ERalpha) revealed that homozygous mutant females simply would not do lordosis behavior and instead were extremely aggressive, thus identifying a specific gene as essential for a mammalian social behavior. In dramatic contrast, ERbeta knockout females can exhibit normal lordosis behavior. With the understanding, in considerable mechanistic detail, of how the behavior is produced, now we are also studying brain mechanisms for the biologically adaptive influences which constrain reproductive behavior. With respect to cold temperatures and other environmental or metabolic circumstances which are not consistent with successful reproduction, we are interested in thyroid hormone effects in the brain. Competitive relations between two types of transcription factors - thyroid hormone receptors and estrogen receptors have the potential of subserving the blocking effects of inappropriate environmental circumstances on female reproductive behaviors. TRs can compete with ERalpha both for DNA binding to consensus and physiological EREs and for nuclear coactivators. In the presence of both TRs and ERs, in transfection studies, thyroid hormone coadministration can reduce estrogen-stimulated transcription. These competitive relations apparently have behavioral consequences, as thyroid hormones will reduce lordosis, and a TRbeta gene knockout will increase it. In sum, we not only know several genes that participate in the selective control of this sex behavior, but also, for two genes, we know the causal routes. Estrogenic hormones are also the foci of widespread attention for their potential therapeutic effects improving, for example, certain aspects of mood and cognition. The former has an efficient animal analog, demonstrated by the positive effects of estrogen in the Porsolt forced swim test. The latter almost certainly depends upon trophic actions of estrogen on several fundamental features of nerve cell survival and growth. The hypothesis is raised that the synaptic effects of estrogens are secondary to the trophic actions of this type of hormone in the nucleus and nerve cell body.

Affect↗
PubMed1985

The proestrous surge of prolactin enhances sexual receptivity in the rat.

The influence of the proestrous surge of prolactin (Prl) on expression of feminine sexual behavior (lordosis) has been investigated. In the first experiment, proestrous rats were treated with a dopamine agonist, bromocriptine (CB-154; 100 micrograms at 1200, 1300, and 1600 h), which blocked the proestrous surge of Prl without affecting the preovulatory surge of luteinizing hormone. Such animals displayed depressed lordosis quotients (LQs) when compared to control animals at 2000 h on proestrus. However, in CB-154-treated animals given ovine Prl (10 I.U.) at 1400 h on proestrus, LQs were restored to control levels. Ovariectomized (OVX) rats primed with estradiol benzoate (EB; 2 micrograms for 2 days) produced surges of Prl that were similar in timing to those of proestrous. Once again, CB-154 treatment blocked this Prl surge and significantly depressed the LQ, whereas replacement with ovine Prl returned the LQ to control values. These results suggest that the Prl surge facilitates the expression of lordosis. Ovariectomized/adrenalectomized (ADX) and OVX/sham ADX rats were treated with EB (2 micrograms for 2 days) and tested for lordosis on Day 3. Adrenalectomized rats responded with lower levels of lordosis than did sham controls. Administration of progesterone (P4) to ADX rats on Day 3 enhanced the LQ compared to sham ADX values. CB-154 was ineffective in reversing the enhanced LQ, indicating that Prl may be acting through stimulation of adrenal progestins. These data taken together suggest that the proestrous surge of Prl contributes to the normal expression of feminine sexual behavior on proestrus.

Adrenalectomy↗
PubMed1985

Radiographic measurement of the lumbar spine. A clinical and experimental study in man.

The accuracy of radiographic measurements of lumbosacral lordosis, vertebral size, spondylolisthesis, and disc height were studied. Errors caused by lateral tilt or longitudinal axis rotation of the lumbosacral spine were assessed in an experimental study on 12 cadavers. In a series of 170 normal individuals, the distribution of radiographic variables describing lumbosacral lordosis, size of vertebrae, and disc height was investigated. The interobserver measurement variation was studied with respect to all measured variables. The differences between radiographs of 125 spondylolytic patients in the recumbent and standing positions were analyzed with respect to vertebral slipping and lumbosacral lordosis. There were only minor projectional and interobserver measurement errors in the variables describing vertebral size and lumbosacral lordosis, which make these variables suitable for radiographic assessment at repeated examination. The absolute measurements of disc height were too inaccurate to be used as a basis for conclusions. A semiquantitative approach is more reliable, and can be recommended for the comparison of radiographic assessments of disc height. In adults, the radiographic evaluation of vertebral slipping and lumbosacral lordosis is equally reliable in the recumbent and standing positions.

Adult↗
PubMed1996

The ideal amount of lumbar foraminal distraction for pedicle screw instrumentation.

STUDY DESIGN: A cadaveric study was performed to analyze the changes of foraminal dimensions of the lumbar spine and also to estimate the amount of foraminal distraction, achieved with pedicle screw instrumentation, that will create the greatest improvement in foraminal dimensions. OBJECTIVES: To establish the ideal amount of lumbar foraminal distraction using pedicle screw instrumentation and to investigate the changes of adjacent segments and lumbar lordosis with distraction maneuvers. SUMMARY OF BACKGROUND DATA: In patients undergoing fusions and instrumentation for foraminal stenosis, distraction of the lumbar spine may improve the dimensions of the intervertebral foramen. Results of previous studies have shown that anterior interbody distraction of the lumbar spine significantly increased the space in the lumbar foramen. No previous study has assessed the ideal amount of distraction, changes in the adjacent segments, or the effect on lumbar lordosis using posterior pedicle screw instrumentation. METHODS: Six fresh frozen human cadaveric spines from 15 to the sacrum were used. The ISOLA instrumentation system (Acromed Inc., Cleveland, OH) was applied using pedicle screws at L4, L5, and S1, L4-L5 and L5-S1 rods were contoured to the same degree of lumbar lordosis as in the specimen. The spine was potted in the upright position with the sacrum secured in the mold, and an axial load of 40 pounds was applied to the specimen. Radiographs were used to measure the posterior disc height, foraminal height, foraminal area, and lumbar lordosis. Two mm, 4 mm, 6 mm, 8 mm, and 10 mm of single level distraction were added to L4-L5 and L5-S1. The dimensions of the specimen were digitized and calculated after each distraction. RESULTS: The posterior disc height, foraminal height and foraminal area increased with distraction. The greatest incremental change in the foraminal area was noted at 6 mm of distraction. The L4-L5 foraminal area increased 22.6% at 6 mm of L4-L5 distraction, and the L5-S1 foraminal area increased 39.2% at 6 mm of L5-S1 distraction. With distraction above 6 mm, the foraminal change plateaued. The greatest decrease in lumbar lordosis was only 4.6 degrees and occurred at 10 mm of distraction. There was no significant effect of distraction on the foramina of adjacent levels. CONCLUSION: Posterior distraction using pedicle screws increased foraminal dimensions. The ideal amount of distraction on the rod, or the minimal amount of distraction necessary for improving foraminal dimensions, may be 6 mm using pedicle screw instrumentation.

Aged↗
PubMed1979

Facilitation of female reproductive behavior from mesensephalic central gray in the rat.

Electrical stimulation in the mesencephalic central gray (CG) and adjacent subtectum through chronically implanted electrodes in free-moving estrogen-primed ovariectomized female rats elicited a rapid and large facilitation of the lordosis reflex in response to either male mounts or manula cutaneous stimuli. Unilateral stimulation was sufficient for this effect. The facilitation increased in a graded manner to increased stimulus intensity, and was optimally evoked by stimuli delivered at 50--150 Hz. Facilitation disappeared rapidly following the end ot electrical stimulation, and within 15 min, reflex performance returned to the prestimulation level. Lordosis facilitation appeared when no aversive responses occurred; stimulation with comparable parameters at the lateral edge of CG or in the mesencephalic reticular formation often resulted in postural changes or aversive responses but was not able to facilitate lordosis. Lordosis refelx facilitation was probably mediated by projections descending from neurons in and around the CG, and represents stimulation of a functional link between ascending somatosensory and descending motor systems for the control of lordosis behavior.

Animals↗
PubMed1976

Hypophysectomy facilitates sexual behavior in female rats.

Lordosis was elecited in 49% of 87 hormonally untreated, hypophysectomized-ovariectomized (hypox-ovx) female rats in response to palpation of the flanks and perineum (vaginal stimulation was not applied). By contrast, only 12% of 113 hormonally untreated ovariectomized (ovx) rats showed lordosis in response to such stimulation. Subsequently, hypox-ovx and ovx-only rats were given daily injections of 1 mug/kg estradiol benzoate (EB) and tested for sexual receptivity with males. Teh estrogen-treated hypox-ovx females became sexually receptive significantly earlier, and exhibited higher lordosis quotients and more soliciting behavior, than the estrogen-treated ovx-only rats. The increased sexual responsiveness in the hypox-ovx rats could be due to increased LRH activity. To test this, we treated hypox-ovx rats with dihydrotestosterone propionate (DHT-P), which suppresses plasma LH levels but is relatively ineffective in inducing sexual receptivity, and found a significant depression of lordosis responsiveness. These experiments suggest that hypox-ovx females show a heightened responsiveness to hormonal and/or sensory factors that induce a lordosis response, possibly because of increased LRH activity.

Animals↗