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PubMed2006

Effect of different sitting postures on lung capacity, expiratory flow, and lumbar lordosis.

OBJECTIVE: To investigate the effect of sitting posture on lung capacity and expiratory flow (LC-EF) and lumbar lordosis. DESIGN: Repeated measures on 1 group of subjects in 4 postures. SETTING: Laboratory. PARTICIPANTS: Seventy able-bodied volunteers. INTERVENTIONS: Postures were assumed randomly: normal, with full ischial support and flat lumbar support; slumped, with the pelvis positioned in the middle of seat while leaning against the backrest; against the back part of the seat without ischial support (WO-BPS), with partially removed ischial support and an enhanced lumbar support; and standing. MAIN OUTCOME MEASURES: For LC-EF, forced vital capacity, maximum forced expiratory flow, forced expiratory volume in 1 second, and peak expiratory flow; and lumbar lordosis. RESULTS: All LC-EF measures in standing were significantly superior to those in slumped and normal sitting, and 4 measures were significantly higher than in WO-BPS. In slumped sitting, LC-EF significantly decreased from that in normal sitting. WO-BPS sitting significantly increased 4 of the LC-EF measures from those in the normal sitting. Lumbar lordosis was the highest in standing and progressively decreased in WO-BPS, normal, and slumped sitting. CONCLUSIONS: Slumped sitting significantly decreased LC-EF and lumbar lordosis. Because it increases the lumbar lordosis and promotes LC-EF, the WO-BPS posture may be a better seating option for people sitting for a prolonged time.

Adult↗
PubMed2007

Reproduction of the lumbar lordosis: a comparison of standing radiographs versus supine magnetic resonance imaging obtained with straightened lower extremities.

OBJECTIVE: This study investigates whether it is possible to reproduce the lumbar lordosis in the upright position during magnetic resonance imaging (MRI) by positioning the patient supine with straightened lower extremities and investigates intra- and interexaminer reliability of measurements of the lumbar lordosis on radiographs and MRI. METHODS: This was an observational study, which included an intra- and interexaminer reliability study. The lumbar lordosis was measured digitally on radiographs taken from 22 patients in an upright standing position, and 22 MRI scans of the same patients lying supine with straightened lower extremities. These measurements were compared statistically. Intra- and interexaminer reliability was calculated applying the Bland and Altman method. RESULTS: The lumbar lordosis in the standing position was reproduced in the straightened supine position with a median deviation of 3 degrees . Intra- and interexaminer reliability was better for MRI than for radiographs. The mean differences were close to 0, especially for interexaminer reliability during MRI. On radiographs, there was a higher agreement on interexaminer than on intra-examiner reliability. CONCLUSION: The findings of this study show that lumbar lordosis in the upright position can be reproduced by positioning the patient supine with straightened lower extremities.

Female↗
PubMedDate not supplied

Increasing the cervical lordosis with chiropractic biophysics seated combined extension-compression and transverse load cervical traction with cervical manipulation: nonrandomized clinical control trial.

BACKGROUND: Cervical lordosis has been shown to be an important outcome of care; however, few conservative methods of rehabilitating sagittal cervical alignment have been reported. OBJECTIVE: To study whether a seated, retracted, extended, and compressed position would cause tension in the anterior cervical ligament, anterior disk, and muscle structures, and thereby restore cervical lordosis or increase the curvature in patients with loss of the cervical lordosis. STUDY DESIGN: Nonrandomized, prospective, clinical control trial. METHODS: Thirty preselected patients, after diagnostic screening for tolerance to cervical extension with compression, were treated for the first 3 weeks of care using cervical manipulation and a new type of cervical extension-compression traction (vertical weight applied to the subject's forehead in the sitting position with a transverse load at the area of kyphosis). Pretreatment and posttreatment Visual Analogue Scale (VAS) pain ratings were compared along with pretreatment and posttreatment lateral cervical radiographs analyzed with the posterior tangent method for changes in alignment. Results are compared to a control group of 33 subjects receiving no treatment and matched for age, sex, weight, height, and pain. RESULTS: Control subjects reported no change in VAS pain ratings and had no statistical significant change in segmental or global cervical alignment on comparative lateral cervical radiographs (difference in all angle mean values < 1.3 degrees ) repeated an average of 8.5 months later. For the traction group, VAS ratings were 4.1 pretreatment and 1.1 posttreatment. On comparative lateral cervical radiographs repeated after an average of 38 visits over 14.6 weeks, 10 angles and 2 distances showed statistically significant improvements, including anterior head weight bearing (mean improvement of 11 mm), Cobb angle at C2-C7 (mean improvement of -13.6 degrees ), and the angle of intersection of the posterior tangents at C2-C7 (mean improvement of 17.9 degrees ). Twenty-one (70%) of the treatment group subjects were followed for an additional 14 months; improvements in cervical lordosis and anterior weight bearing were maintained. CONCLUSIONS: Chiropractic biophysics (CBP) technique's extension-compression 2-way cervical traction combined with spinal manipulation decreased chronic neck pain intensity and improved cervical lordosis in 38 visits over 14.6 weeks, as indicated by increases in segmental and global cervical alignment. Anterior head weight-bearing was reduced by 11 mm; Cobb angles averaged an increase of 13 degrees to 14 degrees; and the angle of intersection of posterior tangents on C2 and C7 averaged 17.9 degrees of improvement.

Adult↗
PubMed2002

Comparison of lumbar range of movement and lumbar lordosis in back pain patients and matched controls.

Inconclusive findings have been shown in previous studies comparing lumbar range of movement (LROM) and lumbar lordosis between back pain patients and healthy subjects. In these studies, confounding variables such as age, gender, height, obesity, and pain level were usually not well controlled. The present study aimed to compare LROM and lumbar lordosis between back pain patients and matched controls. Fifteen male back pain patients and 15 age-, height-, obesity-, and physical activity-matched male controls were investigated. To minimize the effect of pain on the measurements, only patients with minimal or no pain at the time technique was used for the evaluation of LROM in flexion, extension and lateral flexion as well as lumbar lordosis. A lumbar rotameter was used for measuring axial rotation. Pelvic motion was limited by a pelvic restraint device during LROM measurements. Results showed that there were no significant differences between the back pain and control groups in flexion, extension, lateral flexion and axial rotation LROM and also in lumbar lordosis. This may indicate that when a back pain patient is not in pain, LROM and lumbar lordosis may not be the measures that distinguish between back pain patients and subjects without back pain.

Adult↗
PubMed1985

The lumbar lordosis in acute and chronic low-back pain.

To evaluate a possible relationship between the amount of lumbar lordosis in asymptomatic as well as subjects with acute and chronic low-back pain, the amount of lordosis was determined from spinal roentgenograms of 600 men between 20 and 63 years of age. The angle between a line parallel to the cranial end-plate of L1 and S1 was defined as the lordosis angle. The amount of lordosis was distributed similarly according to age within each of the three groups and was also similar in comparisons between the groups. The men were randomly selected to represent three different groups. Each group included 200 age-matched subjects with similar occupation. The first group consisted of men claiming no previous back-pain history who underwent spinal x-ray as a part of a preemployment examination. The second group consisted of men who had a spinal x-ray examination after claiming their first low-back injury, but not preemployment screening. The third group consisted of x-ray examination of men evaluated for chronic low back disability. The findings thus indicated that the distribution and range of lordosis as viewed by clinicians and radiologists does not vary in the acute or with chronic low-back pain, more than in men without back pain of the same age.

Acute Disease↗
PubMed1996

Measurement of lumbar lordosis. Evaluation of intraobserver, interobserver, and technique variability.

STUDY DESIGN: Sixty radiographs were measured on two separate occasions by three physicians using four different techniques to evaluate the reliability and reproducibility of the measurement of lumbar lordosis. OBJECTIVE: To evaluate clinical methods of measuring lumbar lordosis, determining intraobserver and interobserver reliability. SUMMARY OF BACKGROUND DATA: Several different methods are used to measure lumbar lordosis. The reliability and reproducibility of these has not been well studied. METHODS: Sixty lateral full spine radiographs were obtained, labeled, and the lumbar lordosis measured independently by three practitioners who routinely perform these measurements. Four measurement techniques were used. These included measurements from the inferior endplate of T12 to the superior endplate of S1; the superior endplate of L1 to the superior endplate of S1; the inferior endplate of T12 to the inferior endplate of L5; and the superior endplate of L1 to the inferior endplate of L5. The measurements then were repeated after relabeling. RESULTS: Intraobserver reliability coefficients ranged from 0.83 to 0.92, indicating excellent reproducibility. Ninety-two percent of repeat measures were within 10 degrees. High overall and pairwise agreement among the three observers also was present; the interobserver reliability coefficients ranged from 0.81 to 0.92. CONCLUSIONS: The measurement of lumbar lordosis is reproducible and reliable if the technique is specified and one accepts 10 degrees as acceptable variation. Factors that affect the reproducibility of measurement include end vertebra selection (especially with transitional segments) and vertebral endplate architecture.

Adult↗
PubMed2004

Segmental lumbar lordosis: manual versus computer-assisted measurement using seven different techniques.

OBJECTIVES: Obliteration of end-plate landmarks by interbody fusion has made the traditional measurement of segmental lumbar lordosis nearly impossible. Because the L4-L5 and L5-S1 levels are most likely to be subjected to fusion procedures or arthroplasty and contribute to more than half of normal lumbar lordosis, it is crucial to identify a reproducible and accurate means of measuring segmental lordosis at these levels. METHODS: Twelve spinal surgeons measured lordosis at L4-L5 and L5-S1 on 10 separate radiographs using three techniques for L4-L5 and four techniques for L5-S1. With use of identical radiographs, measurements first were made using a manual method and then were repeated with a computer-assisted method. Measurements were analyzed for both intraobserver and interobserver error. RESULTS: The individual data demonstrated an intraobserver variance of 9.56 and a standard deviation of 3.092 for computerized measurements compared with 7.742 and 2.782 for manual measurements. The interobserver variance was 4.107 with a standard deviation of 2.027 for the computerized group compared with 4.221 and 2.055 for manual measurements. When analyzed as a group to evaluate interobserver error, the pooled data yielded variance of 19.235 for the computerized group and 19.117 for the manual measurements. CONCLUSIONS: Variance calculations identified the Cobb technique and the posterior vertebral body technique as the least variable measurement techniques for the L4-L5 and L5-S1 levels, respectively; however, there was no statistical significance. In direct comparison, the manual and computer-assisted techniques were found to be statistically equivalent with similar degrees of variance. We believe that the anterior vertebral technique, which did not demonstrate a significant difference from other techniques, will prove to be the most reliable method of assessing segmental lumbar lordosis in patients before surgery, after interbody fusion, and after motion-sparing disc arthroplasty.

Artifacts↗
PubMed1983

Radiographic determination of lordosis and kyphosis in normal and scoliotic children.

We conducted a radiographic retrospective study in children to determine spinal lordosis and kyphosis. A total of 218 lateral standing full-length radiographs were studied: 104 normal and 114 scoliotic patients. Normal X-ray films were defined as those obtained for suspected disorder (e.g., scoliosis) with no abnormalities detected by the radiologist or orthopedist. Thoracic kyphosis is defined as the angle between perpendiculars drawn from the inferior endplate of T5 and the superior endplate of T12. Lordosis is the angle between perpendiculars from the inferior endplate of L1 and the superior endplate of L5. The angle between the inferior endplate of L5 and the top of the sacrum is the L5-S1 angle. Statistical analysis was undertaken to compare lordosis and kyphosis radiographic measurements with age, sex, height, and weight employing the SAS package program. No significant relationships were noted between degree of scoliosis, age, sex, height or weight, and kyphosis, lordosis, or L5-S1 angle. Neither could correlations among the three radiographic measurements be made. Lordosis measured 40 degrees (range 31-49.5 degrees) in normal and 48.5 degrees (range 40-55 degrees) in scoliotic patients. Kyphosis measured 27 degrees (range 21-33 degrees) in normal and 28 degrees (range 16.5-36 degrees) in scoliotic patients.

Adolescent↗
PubMed2000

Lumbar lordosis and pelvic inclination in adults with chronic low back pain.

BACKGROUND AND PURPOSE: The causes of lumbopelvic imbalances in standing have been widely accepted by physical therapists, but there is a lack of scientific evidence available to support them. We examined the association between 9 variables and pelvic inclination and lumbar lordosis during relaxed standing. SUBJECTS: Thirty men and 30 women with chronic low back pain (CLBP) for at least 4 months were examined (mean age=54.9 years, SD=9, range=40.4-69.8). METHODS: Multiple linear regression modeling was used to assess the association of pelvic inclination and the magnitude of lumbar lordosis in standing with age, sex, body mass index (BMI), Oswestry Back Pain Disability Questionnaire (ODQ) scores, physical activity level, hip flexor muscle length, abdominal muscle force, and range of motion (ROM) for lumbar flexion and extension. RESULTS: In women, age, BMI, and ODQ scores were associated univariately and multivariately with pelvic inclination. In men, lumbar extension ROM was related univariately to pelvic inclination; age, lumbar extension ROM, and ODQ scores were associated multivariately. Lumbar lordosis was associated univariately with only lumbar extension ROM for women and men. A weak correlation was found between angle of pelvic inclination and magnitude of lumbar lordosis in standing (r=. 31 for women, r=.37 for men). CONCLUSION AND DISCUSSION: The odds ratio of having CLBP is increased if the score on the double-leg lowering test for abdominal muscles exceeds 50 degrees for men and 60 degrees for women. In patients with CLBP, the magnitude of the lumbar lordosis and pelvic inclination in standing is not associated with the force production of the abdominal muscles.

Adult↗
PubMed1997

Radiographic mensuration characteristics of the sagittal lumbar spine from a normal population with a method to synthesize prior studies of lordosis.

Standing lateral lumbar radiographs of 50 normal healthy subjects were retrospectively selected for evaluation of lumbar lordosis. The objective was to evaluate, in a normal population, global and segmental contributions to lordosis in the standing position, and to devise a method to compare the seemingly unrelated multitude of lordotic values in the literature. Because of a variety of positioning and measurement methods of lordosis in live subjects and cadavers, correlation of results is difficult. While often relying on simple pain questionnaires, studies of normal subjects rarely have complete medical history, physical, neurological, and orthopedic examinations. Standing lateral lumbar radiographs of 50 subjects, who had complete histories and normal examinations, were analyzed to determine overall lordosis, segmental contributions, and vertical sagittal alignment. Using posterior body tangents, the mean L1-L5 angle was -39.7 degrees, CobbT12-S1 = -65 degrees, Ferguson's sacral angle = 39 degrees, pelvic tilt angle was 49 degrees, and average RRAs (segmental angles) were RRAT12-L1 = -3.6 degrees, RRAL1-L2 = -4.1 degrees, RRAL2-L3 = -7.6 degrees, RRAL3-L4 = -11.7 degrees, RRAL4-L5 = -16.8 degrees, and RRAL5-S1 = -32.4 degrees. Using segmental rotation angles as a method to compare past and current literature, a normal standing lumbar lordosis of CobbT12-S1 = -61 degrees, range -55 degrees to -65 degrees, was determined with specific segmental angles.

Adolescent↗
PubMed1994

Opiate receptor blockade enhances the display of progesterone-facilitated lordosis in juvenile female guinea pigs.

Juvenile female guinea pigs rarely display estradiol-induced or progesterone-facilitated sexual receptivity. This experiment was designed to test the hypothesis that endogenous opiate peptides tonically inhibit the display of steroid-induced lordosis in juvenile females. Hartley guinea pigs were ovariectomized (OVX) at 10-11 days of age and treated with estradiol benzoate (EB, 10 micrograms) 5-7 days later. Injection of the opiate antagonist, naloxone (2.0 mg/kg), did not facilitate lordosis (compared to vehicle) in EB-primed, OVX juveniles; when these animals were subsequently given progesterone, and the treatment groups were reversed (i.e., the group previously treated with vehicle received 2.0 mg/kg naloxone 4.5 hr after progesterone, and vice versa), four of six naloxone-injected animals displayed lordosis, compared to one of six control animals. In a second experiment, a range of doses of naloxone was administered to EB-plus progesterone-treated OVX juveniles. Naloxone at the 2.0 mg/kg dose resulted in a significant increase in the percentage of females displaying lordosis, with lower doses (0.5-1.0 mg/kg) producing responses intermediate between those observed in animals receiving the 2.0 mg/kg dose and the vehicle. Furthermore, the facilitatory effect of naloxone on sexual receptivity was completely blocked by concomitant injection of morphine (10.0 mg/kg). These data suggest that endogenous opiates tonically inhibit the display of progesterone-facilitated lordosis in juvenile female guinea pigs.

Animals↗
PubMed1995

Progesterone-facilitated lordosis in medial preoptic area-lesioned, juvenile guinea pigs.

Juvenile female guinea pigs rarely display lordosis in response to estradiol and progesterone treatments that elicit sexual receptivity in adults. To test the hypothesis that the medial preoptic area (MPOA) tonically inhibits the display of steroid-induced lordosis in juveniles, 11-day-old guinea pigs were ovariectomized (OVX) and received bilateral, sham, or electrolytic lesions aimed at the MPOA 3-4 days later. At 20-22 days of age, these females were tested for the expression of sexual receptivity following injections of estradiol benzoate (EB, 10 micrograms s.c.) and progesterone (0.5 mg s.c., 40 h after EB). The lesions damaged portions of the MPOA, the nucleus of the diagonal band of Broca, the lateral aspect of the medial preoptic nucleus, the medial part of the preventricular portion of the periventricular nucleus, and the anterior commissure. The lesions did not alter the display of estradiol-induced lordosis. However, after treatment with EB plus progesterone, 20% of the sham-lesioned females displayed lordosis, as compared to 80% of the MPOA-lesioned animals. These data are consistent with the hypothesis that neurons originating in and/or traversing the MPOA tonically suppress the display of progesterone-facilitated lordosis in juvenile guinea pigs. Removal of this inhibitory input allows prepubertal females to respond behaviorally to estradiol and progesterone in an adult-typical fashion.

Animals↗
PubMed1997

Lordosis in male rats: effect of dorsal raphe nucleus cuts.

The efferents and/or afferents of the dorsal raphe nucleus (DRN) were transected by several types of cut in castrated male rats, and lordosis behavior was observed after implantation with Silastic tubes containing estradiol. Throughout the behavioral tests, low incidences of lordosis were observed in control male rats without brain surgery or with a sham operation. In contrast, all male rats with a horizontal circle cut at the ventral area of the DRN displayed lordosis, and the mean lordosis quotient (LQ) was higher than that in control rats, while rats with a horizontal cut at the dorsal area of the DRN did not. Furthermore, mean LQs in male rats with an anterior half-circle horizontal cut at the ventral area of the DRN were higher than those in control groups. A posterior half-circle cut at the ventral area had no effect. In addition, male rats with a half-dome cut located anterior to the DRN showed a high LQ score, but rats with a posterior half-dome cut did not. These results suggest that anterior and anteroventral neural fibers of the DRN are involved in the lordosis inhibiting mechanism in male rats.

Afferent Pathways↗
PubMed2006

Mid-aged and aged wild-type and progestin receptor knockout (PRKO) mice demonstrate rapid progesterone and 3alpha,5alpha-THP-facilitated lordosis.

RATIONALE: Progesterone (P) and its 5alpha-reduced metabolite, 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP), facilitate sexual behavior of rodents via agonist-like actions at intracellular progestin receptors (PRs) and membrane GABA(A)/benzodiazepine receptor complexes (GBRs), respectively. OBJECTIVE: Given that ovarian secretion of progestins declines with aging, whether or not senescent mice are responsive to progestins was of interest. METHODS: Homozygous PR knockout (PRKO) or wild-type mice that were between 10-12 (mid-aged) or 20-24 (aged) months of age were administered P or 3alpha,5alpha-THP, and the effect on lordosis were examined. Effects of a progestin-priming regimen that enhances PR-mediated (experiment 1) or more rapid, PR-independent effects of progestins (experiments 2 and 3) on sexual behavior were examined. Levels of P, 3alpha,5alpha-THP, and muscimol binding were examined in tissues from aged mice (experiment 4). RESULTS: Wild-type, but not PRKO, mice were responsive when primed with 17beta-estradiol (E(2); 0.5 microg) and administered P (500 microg, subcutaneously). Mid-aged wild-type mice demonstrated greater increases in lordosis 6 h later compared to their pre-P, baseline test than did aged wild-type mice (experiment 1). Lordosis of younger and older wild-type, but not PRKO, mice was significantly increased within 5 min of intravenous (IV) administration of P (100 ng), compared with E(2)-priming alone (experiment 2). However, wild-type and PRKO mice demonstrated significant increases in lordosis 5 min after IV administration of 3alpha,5alpha-THP, an effect which was more pronounced in mid-aged than in aged animals (100 ng-experiment 3). In tissues from aged wild-type and PRKO mice, levels of P, 3alpha,5alpha-THP, and muscimol binding were increased by P administration (experiment 4). PR binding was lower in the cortex of PRKO than that of wild-type mice. CONCLUSIONS: Mid-aged and aged PRKO and wild-type mice demonstrated rapid P or 3alpha,5alpha-THP-facilitated lordosis that may be, in part, independent of activity at PRs.

Aging↗
PubMed1976

Brain stem and cerebellar lesions in female rats. II. Lordosis reflex.

The effects of brain stem and cerebellar lesions upon the lordosis reflex were studied. Lesions of the lateral vestibular nucleus (LVN) and nucleus reticularis gigantocellularis (NGc) produced significant deficits in lordosis. Lesions of the deep cerebellar nuclei, inferior olive, medial vestibular nucleus, and superior vestibular nucleus did not produce significant effects. Results from animals with lesions of both lateral vestibular nucleus (LVN) and nucleus gigantocellularis (NGc) suggested that these structures act independently in their control of lordosis. Histological analysis showed that giant cell loss in NGc and Deiters' cell loss in LVN were both significantly correlated with decrements in lordosis. These results indicate that lateral vestibulospinal and reticulospinal pathways participate in the descending control of segmental mechanisms responsible for the lordosis reflex.

Animals↗
PubMed1976

Sensory requirements for the lordosis reflex in female rats.

(1) Visual, auditory and olfactory input were not necessary for the performance of the lordosis reflex by female rats. Since taste is not involved in this behavior, somatosensory input must be sufficient for triggering the lordosis reflex. (2) Surgical cutaneous denervation markedly reduced the frequency and strength of lordosis. The most effective operation denervated the perineum, tailbase, posterior rump and ventral flanks. This pattern of results agrees with film observations and manual stimulation of lordosis. (3) Effects of surgical cutaneous denervation were confirmed in experiments with local anesthesia produced by subcutaneous procaine injections. (4) It is deduced that cutaneous mechanoreceptors in specific regions of hairy skin of the female rat play a crucial role in triggering the lordosis reflex.

Animals↗
PubMed1992

Alpha 1-adrenergic agonists act on the ventromedial hypothalamus to cause neuronal excitation and lordosis facilitation: electrophysiological and behavioral evidence.

To see if activation of central alpha 1-adrenergic receptors can cause facilitation of lordosis in rats, the behavioral effects of centrally administered alpha 1-agonists, methoxamine (MA) and phenylephrine (PhE), and related agents were studied. In ovariectomized rats treated with estrogen, infusion of MA, PhE, or a beta-agonist isoproterenol, into the lateral ventricle, or bilateral infusions of MA or PhE into the ventromedial hypothalamus (VMH) facilitated lordosis. Conversely, intra-VMH infusion of the alpha 1-antagonist prazosin (PZ) inhibited lordosis. Intra-VMH infusion of isoproterenol or an alpha 2-agonist clonidine, had no effect. Neither was the intra-VMH infusion of MA effective if: (i) the rats were not primed with estrogen; (ii) the tips of the cannulae were outside the VMH; or (iii) it was preceded by an intra-VMH infusion of the alpha 1b-antagonist, chloroethylclonidine (CEC). These results not only verify implications from recent studies that alpha 1-receptors in the hypothalamus are important for lordosis facilitation, but further show that the adrenergic facilitatory effect are: (i) mediated specifically by alpha 1b-subtype of the alpha 1-receptor, (ii) estrogen-dependent, and (iii) site-specific to VMH. To investigate neural mechanisms potentially underlying the lordosis-facilitating effect of alpha 1-activation, the actions of MA and PhE on the electrical activity of single neurons of the ventromedial nucleus of the hypothalamus (VMN) in vitro were studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗
PubMed1994

Activation of protein kinase C in the hypothalamic ventromedial nucleus or the midbrain central gray facilitates lordosis.

Many neurotransmitters and neuropeptides can act through the hypothalamic ventromedial nucleus (VMN) or midbrain central gray (MCG) to facilitate lordosis. Since these lordosis-facilitating agents can also stimulate the phosphoinositide (PI) second-messenger pathway, it was hypothesized that direct activation of this pathway can also potentiate the behavior. To evaluate this possibility, a phorbol ester, TPA (12-O-tetradecanoyl phorbol 13-acetate), was used to activate a key enzyme, protein kinase C (PKC), of the PI pathway in ovariectomized (OVX) rats either primed or not primed with estrogen. These female rats were paired with males for mating tests before and after an intracerebral infusion of TPA, and both the lordosis quotient (LQ) and the lordosis strength (LS) were measured. Bilateral infusion of TPA (5 micrograms/0.5 microliter or 0.2 microgram/0.2 microliter, but not 0.1 microgram/0.2 microliter/side) into the VMN or MCG of estrogen-primed subjects facilitated both LQ and LS in 30 min, peaked at 60-90 min, and the facilitation lasted for more than 180 min. This facilitatory effect of TPA was: (1) not observed in OVX rats not primed with estrogen; (2) not observed if the infused TPA did not reach both sides of the VMN or MCG; (3) not mimicked by 4 alpha-phorbol 12,13-didecanoate, which does not activate PKC; (4) blocked by PKC inhibitors (H7 10 mM or staurosporine 1 microM, 0.2 microliter/side), which by themselves did not facilitate lordosis; and (5) was not affected by pretreatment of the progestin antagonist RU486.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaloids↗