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PubMed2005

A lumbar classification of scoliosis in the adult patient: preliminary approach.

STUDY DESIGN: Retrospective consecutive clinical review of 98 patients. OBJECTIVE: To create a preliminary approach to a clinically important classification of scoliosis in adult patients. SUMMARY OF BACKGROUND DATA: There is currently no accepted classification of scoliosis in adults. High prevalence rates of scoliosis in the elderly and recent studies of health impact support the need for a clinically relevant classification. METHODS: A total of 98 adult patients with scoliosis with a 2-year minimum treatment/follow-up were included. Patients were classified into one of 3 types of deformity based on the degree of lordosis (L1-S1) and frontal plane endplate obliquity of L3 on standing radiographs: type I = lordosis > 55 degrees, L3 obliquity < 15 degrees; type II = lordosis 35 degrees-55 degrees, L3 obliquity 15 degrees-25 degrees; and type III = lordosis < 35 degrees, L3 obliquity > 25 degrees. RESULTS: Curve patterns included thoracic, thoracolumbar, lumbar, thoracic, and lumbar (mean Cobb angle 30 degrees, standard deviation 19 degrees). Cobb angle revealed no correlation to visual analog pain score (VAS) or general health (36-Item Short-Form Health Survey). Significant correlation between endplate obliquity L3, L1-S1 lordosis and VAS was noted (P < 0.05). Mean pain scores of classified patients were: type I, VAS = 27.7; type II, VAS = 43.3; and type III, VAS = 47.1 (type I vs. III, P < 0.05). Surgical rates (failed minimum 3-month conservative care, including bracing, physical therapy, and pharmacological treatment) by group were: type I, 0%; type II, 9%; and type III, 22.7% (P = 0.002). CONCLUSIONS: A simple classification of adult scoliosis was developed based on frontal and sagittal plane standing radiographs. With increasing type (from I to III), self-reported pain and disability increased. This result was reflected in the treatment approach as well, with surgical rates increasing from types I to III. Further refinement is important to develop an all inclusive and sufficiently descriptive system.

Adult↗
PubMed2000

[Influence of solid thoracolumbar kyphosis on lumbar spine and surgical treatment].

OBJECTIVE: To investigate the influence of solid thoracolumbar kyphosis on the lumbar spine and surgical treatment. METHODS: 14 had solid kyphosis of the thoracolumbar spine. Cobb angle of kyphosis of the thoracolumbar spine and lordosis between L(2)/S(1), L(2)/L(5), L(2)/L(3), L(3)/L(4), L(4)/L(5), L(5)/S(1) pre- and post-osteotomy was measured respectively, and the amount of vertebrae slipped over 3mm was recorded. The results were compared with those of the normal group respectively. RESULTS: The Cobb angles of lordosis between L(2)/S(1), L(2)/L(5), L(2)/L(3), L(3)/L(4), L(4)/L(5), L(5)/S(1) in the deformity group were increased significantly compared with those that of the normal group respectively; obvious changes in percentage occurred in the segment between L(2)/L(3) and L(3)/L(4). Over lordosis of the lumbar spine was greatly corrected postosteotomy of the thoracolumbar spine, it was still significantly different compared with that of the normal group. In 9 patients with retrolisthesis of 20 vertebrae, 70% occurred in L(2) and L(3) vertebrae. The amount of retrolisthesis of vertebrae decreased to 3 in two patients. No retrolisthesis of vertebra was seen in the normal group. Single-stage procedures combined with anterior releasing and posterior osteotomy through facet joints for kyphosis of the thoracolumbar spine showed a correction. rate of 85.7%, but single-stage osteotomy through the posterior vertebra showed a correction rate of 60.7%. Seven of 8 patients who had had seriously back pain complained of no pain or slight backache after operation. 40% of the patients showed functional improvement in the sphincter of the urinary bladder and anus. 50% of the patients had improvement in muscle strength. CONCLUSIONS: Kyphosis of the thoracolumbar spine may result in over lordosis of the lumbar spine and retrolisthesis of vertebrae, which are obvious in the upper lumbar spine. These changes may lead to back pain. Correction of kyphosis of the thoracolumbar spine may obviously decrease over lordosis of the lumbar spine and inclination of vertebral slip, and may further decrease the overload to the posterior column of the spine and relieve back pain. Osteotomy combined with anterior and posterior procedures is effective and safe in the correction of kyphosis of the thoracolumbar spine.

Adolescent↗
PubMed1986

Sagittal profiles of the spine.

The sagittal plane of the growing spine was studied from standardized radiographs of 670 normal subjects to establish standards of reference for thoracic kyphosis, lumbosacral lordosis, and sacral inclination. Cobb's method of measuring spinal deformities was compared with new indices of kyphosis and lordosis that take into consideration the length and width of each curve. Boys and girls had comparable degrees of kyphosis. Although girls initially had higher degrees of lordosis and sacral inclination, by maturity these measurements were similar in both sexes. Significant correlations were found between kyphosis and lordosis and between lordosis and sacral inclination, indicating that these curvatures tend to balance each other.

Adolescent↗
PubMed1994

[Radiological and histological studies on the spinal deformity in hereditary lordoscoliotic rabbits].

The author reports his radiological and histological studies to investigate the etiology of spinal deformities in the Lordoscoliotic Rabbit (LSR), which develops thoracic lordosis or lordoscoliosis during growth. The deformities appeared at 4-6 weeks of age and developed until 16 weeks. Most of them demonstrated lordosis, which was generally seen at the T7-10 levels (44 degrees measured by Cobb's method at maximum), and was often accompanied by slight scoliosis (40 degrees at maximum). Histopathological studies clearly indicated that continuous exposure to non-physiological forces caused a deviation in the nucleus pulposus in the disc, and an extension or compression in the annulus fibrosus, followed by a disproportionate growth of the vertebral body. Histological studies of the vertebral bones showed a specific mode of remodeling in response to the force producing lordosis, and suggested that the force producing lordosis played a major role in the pathogenesis of scoliosis in LSR. These results accord with the recent hypothesis that a reduction in kyphosis or a development of lordosis in the thoracic spine is a responsible factor for human idiopathic scoliosis.

Animals↗
PubMed2001

Transneuronal tracing from sympathectomized lumbar epaxial muscle in female rats.

Pseudorabies virus (PRV) has been used as a transneuronal tracer to study central neural networks, including the central control of the lordosis-producing, lumbar epaxial muscles. Within muscles, however, the sympathetic innervation of blood vessels poses a confounding source of tracer labeling in the CNS. The present study destroyed sympathetic nerves before injection of PRV, thereby allowing for a more selective uptake by somatic motoneurons. Specifically, a focal sympathectomy was created by the injection of dopamine-beta-hydroxylase immunotoxin (DHIT). When PRV was injected into control rats, both somatic motoneurons within the ventral horn of the spinal cord and sympathetic preganglionic neurons within the intermediolateral column (IML) of the spinal cord became labeled. Additionally, labeled neurons were observed in many brain regions, including those previously implicated in the control of the lordosis reflex (e.g., the medullary reticular formation; MRF) and those previously implicated in the control of vasomotor tone (e.g., the rostral ventrolateral medulla; RVLM). When injected into DHIT-pretreated animals, PRV labeling in ventral horn neurons persisted in many animals; however, labeling in IML was eliminated in almost every case. In these animals, PRV labeling was absent in brain areas traditionally associated with vasomotor tone, such as RVLM, whereas labeling persisted in brain areas previously implicated in the control of the lordosis response, such as MRF. The results support the connectivity of spinal and medullary structures with the somatic control of the lordosis-producing muscles and provide a more detailed description of these portions of the putative lordosis-relevant neurocircuitry.

Animals↗
PubMed1993

Facilitation of sexual receptivity by ventromedial hypothalamic implants of the antiprogestin RU 486.

RU 486 is known primarily as an antagonist to progestins and glucocorticoids. However, RU 486 has also been shown to have agonistic progestational properties in biochemical and behavioral studies. In the current study, RU 486 was implanted directly into the ventromedial hypothalamus (VMH) to test for facilitative action on the receptive behavior of female ovariectomized Long-Evans rats primed with 5 micrograms of estradiol benzoate. Cannulae containing RU 486, progesterone (P), or empty cannulae were implanted 48 hr after estrogen priming. The lordosis quotient and the lordosis score were assessed 4 hr after the cannulae were lowered by a standardized test consisting of 10 mounts by a stimulus male. P and RU 486 significantly facilitated receptivity compared to blank implants in terms of lordosis quotient and lordosis score, with no significant difference between the hormone treatments. While only a single dose of each treatment was given in the current study, RU 486 facilitated lordosis when implanted to the VMH as well as progesterone in contrast to our previous results where the steroids were administered systemically.

Animals↗
PubMed1994

Estrogen-induced changes in the neural impulse flow from the female rat preoptic region.

Electrical stimulation of the medial preoptic area (MPO) interrupted the lordosis reflex, the major receptive component of female rat sexual behavior, without interfering with proceptivity. In contrast, axon-sparing MPO lesions with a neurotoxin enhanced lordosis and diminished solicitatory behavior. The MPO effect on the lordosis reflex was mediated by its projection to the ventral tegmental area (VTA) because electrical stimulation of the VTA had a similar effect. In the urethane-anesthetized rats, electrical stimulation of the VTA elicited antidromic action potentials in neurons in the core of the MPO. In the ovariectomized females and neonatally castrated males, but not in the androgenized females, estrogen increased thresholds and prolonged refractory periods for the antidromic activation. Thus the neural effect of estrogen was limited to those animals that showed lordosis in the presence of this steroid. Estrogen also inhibited neurons in the dorsal part of the MPO, which project to the midbrain locomotor region (MLR), but had an opposite excitatory effect on MLR-projection neurons in the medial part of the lateral preoptic area (mLPO). Estrogen may therefore enhance lordosis by reducing neural impulse flow from the MPO to the VTA. A reduced MPO output to the MLR, combined with an augmentation of the mLPO effect, may culminate in increased locomotion in the female rats in estrus, because the MPO suppresses locomotor activity whereas the mLPO facilitates it.

Animals↗
PubMed2001

Spine: posture, mobility and pain. A longitudinal study from childhood to adolescence.

A longitudinal study was undertaken to analyse the development of posture and spinal mobility during growth and its relationship to low back pain and sports activities. A total of 90 children were examined at 5-6 years of age and re-examined at 15-16. Sagittal configuration and mobility were measured using Debrunner's kyphometer. Information about pain and activities was acquired by interview with the parents of the 5- to 6-year-olds and by a questionnaire to the 15- to 16-year-olds. Posture changed significantly during the study period: thoracic kyphosis increased by 6 degrees and lumbar lordosis increased by 6 degrees. The relationship between kyphosis and lordosis was independent of gender at age 5-6, but kyphosis in relation to lordosis was significantly lower in girls among the 15- to 16-year-olds. The total sagittal mobility of the spine decreased significantly during the 10-year study period: in the thoracic spine by as much as 27 degrees and in the lumbar spine by 4 degrees. About one-third of the children at the age of 15-16 years stated that they had occasional low back pain. This complaint was more frequent in those stating they had suffered some type of back injury, but low back pain was not related to gender, regular physical training, posture or spinal mobility. The results of the study showed that kyphosis and lordosis increased and mobility decreased in the 90 children who were examined both at age 5-6 and 15-16 years. The relationship between kyphosis and lordosis decreased in girls but not in boys. Occasional low back pain was reported by 38% of the children at the age of 15-16 years, but back pain was not related to posture, spinal mobility or physical activity.

Adolescent↗
PubMed1976

Pentobarbital inhibition of progesterone-induced behavioral estrus in ovariectomized guinea pigs.

Administration of pentobarbital inhibits the facilitatory effects of progesterone on the release of gonadotropins. In this experiment facilitatory effects of progesterone on lordosis behavior in guinea pigs were examined with pentobarbital anesthesia. Two major animal groups were subjects: one was short-term ovariectomized (2 weeks) and the other was long-term ovariectomized (several months). All animals received estradiol benzoate (6.6 mug s.c.) followed by progesterone (0.4 mg s.c.) 40 h later. Lordosis behavior was induced by the manual stimulation method of Young et al.29 Sodium pentobarbital (30 mg/kg) was injected 8,4 or 2 h before, simultaneously or 1, 2, 6, or 7 h after progesterone. Animals which received pentobarbital slept for 4.5-5 h with subsequent drowsiness for an additional 0.5-1 h. Pentobarbital injections given 8 h before progesterone had no effect on latency to the first lordosis or on other parameters of estrous behavior. However, pentobarbital delayed the onset of heat in estrogen treated ovariectomized guinea pigs when given 4 h before, 2 h before, or simultaneously with progesterone. The delay was directly related to the length of time the animals remained asleep after the progesterone injection, since estrous behavior was invariably displayed with the latency of controls after the animal awoke. Moreover, in animals which were awake for 1-2 h immediately after the progesterone injection before receiving pentobarbital, the latency of recovery from anesthesia to the first display of lordosis was about 1-1.5 h shorter than in the other pentobarbital groups. In contrast to the latency effects of pentobarbital, the duration of heat was unaffected by the anesthetic for all groups mentioned. In animals which received pentobarbital after they were already in heat, pentobarbital injection terminated heat and abolished it completely, since lordosis behavior was not displayed in the hours after recovery from anesthesia. Gross hypothalamic uptake of progesterone was not influenced by pentobarbital administration. Thus, it is tentatively concluded that an incubation period is necessary for progesterone to mediate the display of estrous behavior in the guinea pig in addition to the time necessary for neural uptake. The way in which pentobarbital interferes with the period of progesterone incubation is not currently known.

Animals↗
PubMed1978

Monoamines, estrogen and female sexual behavior in the golden hamster.

In the golden hamster drugs which inhibit monoaminergic function (including p-chlorophenylalanine (PCPA), methysergide and a-methyl-p-tyrosine (a-MPT) facilitated lordosis in ovariectomized female hamsters as a function of the duration of estradiol benzoate (EB) priming. a-MPT (200 mg/kg), methysergide (6 mg/animal) or PCPA (150 or 360 mg/kg) potentiated lordosis if 6 days of EB priming preceded drug treatment. However, if female hamsters were primed with EB for only 2 days, a-MPT and methysergide were ineffective. PCPA (360 mg/kg) was less effective after 2 days of EB than after 6 days of EB priming. alpha-MPT produced a three-fold elevation in progesterone levels in ovariectomized females but methysergide and PCPA did not influence serum progesterone. PCPA (360 mg/kg) facilitated lordosis in adrenalectomized, ovariectomized females, eliminating the possibility that adrenal progesterone is essential for the behavioral effects of the drug. Luteinizing hormone-releasing hormone levels in the preoptic/anterior hypothalamic area and the medial basal hypothalamus were also not significantly altered at 1 h after PCPA injection. Pimozide (1.5 mg/kg) and pimozide (1.5 mg/kg) and amphetamine (2.5 mg/kg) did not potentiate lordosis in ovariectomized hamsters after either 2 or 6 days of EB priming. Pargyline, a monoamine oxidase inhibitor, inhibited female sexual behavior in females in estrogen alone-induced estrus. Lordosis in the female rat is more readily elicited both by drugs and estrogen. It is proposed with regard to female sexual behavior that species differences in estrogen sensitivity may underlie apparent differences in drug sensitivity.

Adrenalectomy↗
PubMed1979

Dissociation of active from immobility components of sexual behavior in female rats by central 6-hydroxydopamine: implications for CA involvement in sexual behavior and sensorimotor responsiveness.

Ovariectomized female rats were given a hormone treatment (2 X 8 micrograms/kg estradiol benzoate) that normally supports only low levels of lordosis responding and no soliciting behavior in tests with sexually active males. When subjected to an intraventricular 6-hydroxydopamine (6-OHDA) procedure (with pargyline pretreatment) that produced 85% and 95% depletions of caudate dopamine and cortical norepinephrine respectively, these females exhibited a dramatic increase in the intensity and frequency of lordotic responding but no soliciting behavior over 3 weekly tests. The increase in lordosis was not due to a drug- or stress-induced release of adrenal progesterone, since dexamethasone suppressed the progesterone levels, as documented by radioimmunoassay, but not the higher receptivity of 6-OHDA treated females. In other ovariectomized females given a hormone regimen (2 X 50 micrograms/kg estradiol benzoate plus 500 micrograms progesterone) that supported maximal levels of lordosis and soliciting, the same 6-OHDA treatment prolonged the average duration of lordosis while actually decreasing the incidence and duration of soliciting. The hypothesis is put forward that the differential effects of interfering with catecholamine, and more likely dopamine function on the soliciting and lordosis components of female sexual behavior might best be understood as a dissociation between mutually antagonistic behavior patterns such that responsiveness involving active orientation and forward locomotion is suppressed, whereas responses requiring immobility are augmented.

Animals↗
PubMed1994

In vitro electrophysiological characterization of midbrain periaqueductal gray neurons in female rats: responses to GABA- and Met-enkephalin-related agents.

Met-Enkephalin, which can be induced by estrogen in the ventromedial nucleus of hypothalamus (VMH), has been proposed to help mediate estrogenic action on lordosis behavior by acting on midbrain periaqueductal gray (PAG) neurons. Also, in the PAG, GABA may locally regulate the levels of lordosis behavior through GABAA receptors. Therefore, we examined the effects of both Met-enkephalin and GABA-related agents on neuronal activity of PAG neurons in slices. Overall, 72.6% of the PAG neurons were inhibited by GABA and 60.9% of GABA-responsive neurons were also excited by the GABAA receptor antagonist, bicuculline methiodide (BMI), suggesting that many of GABA-responsive PAG neurons are tonically inhibited by GABAergic neurons through GABAA receptors. Dorsal PAG neurons were more responsive to BMI than ventral PAG neurons. Moreover, in the middle part of the dorsal PAG, where prominent inhibitory behavioral effects of BMI have been reported, BMI excited 94% of GABA-responsive PAG neurons from estrogen-treated animals, significantly more than observed in ovariectomized control (50%). The most frequent action of Met-enkephalin on PAG neurons was inhibitory (38 out of 149 recorded neurons) although it excited 12 neurons. A dose-dependent increase of inhibitory action of enkephalin was found in the estrogen-primed group but not in the ovariectomized control group while higher doses of enkephalin failed to excite any more neurons in both groups. Most frequently (90%), enkephalin inhibited the same neurons as those on which GABA had the inhibitory effects. Conversely, these neurons composed about 50% of the entire GABA-responsive PAG neurons. Moreover, 76% of neurons inhibited by enkephalin were found to be tonically inhibited by endogenous GABA through GABAA receptors. It is argued, therefore, that increased enkephalinergic influences from the VMH to the PAG in estrogen-treated females could participate in the PAG neuronal control of lordosis by acting on the same neurons as are innervated by intrinsic GABAergic neurons. Since GABAA agonists actually facilitate lordosis in the PAG, these PAG neurons inhibited by both GABA and enkephalin may themselves facilitate behaviors which are antagonistic to lordosis, such as defensive behaviors.

Animals↗
PubMed1992

Intracerebral actions of the 5-HT1A agonists, 8-OH-DPAT and buspirone and of the 5-HT1A partial agonist/antagonist, NAN-190, on female sexual behavior.

Proestrous rats were infused intracerebrally with 50-1000 ng 8-OH-DPAT, 500 or 2000 ng buspirone or 125-500 ng NAN-190. For each drug, bilateral infusions into the mediobasal hypothalamus inhibited female lordosis behavior and proceptivity and initiated resistive behavior. The effects of the drugs were evident within 5-20 min of infusion and generally lasted for 1-2 hr. The effective sites for 5-HT1A-mediated inhibition of sexual behavior were most concentrated in the ventromedial nucleus of the hypothalamus. Cannulae sites anterior, posterior or dorsal to the ventromedial nucleus or clearly within the IIIrd ventricle were less effective at disrupting lordosis behavior. The inhibition of sexual behavior, following 8-OH-DPAT occurred in a dose-dependent manner and appeared to include the loss of motivation of the female to mate. Buspirone produced similar, but quantitatively smaller, effects on lordosis behavior. NAN-190 slightly, but significantly, suppressed lordosis behavior after either intracerebral or intraperitoneal injection and substantially increased resistive behavior. These results suggest that the inhibition of lordosis behavior, following treatment with 5-HT1A agonists, include an action within the ventromedial nucleus. Moreover, 5-HT1A receptors in this area appear to play a functionally important role in the modulation of the female's "willingness" to mate.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1986

Recovery of lordotic activity by dorsal deafferentation of the preoptic area in male and androgenized female rats.

Lordotic activity was examined in male and neonatally androgenized female rats following dorsal deafferentation of the preoptic area (POA). Female pups were injected with various doses (100, 250, 500, or 1000 micrograms) of testosterone propionate (TP) on day 3 postpartum. Ten weeks after birth, all animals were castrated, then half of the castrated males and females in each group were subjected to dorsal deafferentation of the POA (anterior roof deafferentation: ARD) by using an L-shaped Halász knife in order to transect the dorsal forebrain efferents which are thought to exert an inhibitory influence on the lordosis mediating mechanism. Animals were implanted subcutaneously with Silastic tubes containing estradiol-17 beta (E2). Observations of lordosis behavior were carried out 5, 10, and 15 days after implantation of E2. Three to six hours before each behavioral test, all rats were injected with 0.5 mg progesterone. Regardless of the dose of TP given neonatally, androgenized females, as well as males, showed low levels of lordotic behavior. In contrast, males with ARD and androgenized females with ARD displayed lordosis more frequently than males without ARD, and androgenized females without ARD. Lordotic activity in the androgenized females with ARD was negatively correlated with the dose of TP given neonatally. The ARD females injected with a large dose (1000 micrograms) of TP neonatally were significantly less receptive than those injected with lower doses of TP and ARD males. These results suggest that a large dose of neonatal TP may cause permanent changes in not only the neural substrates for lordosis inhibition affected by ARD but also other structures involved in lordosis facilitation.

Animals↗
PubMed1989

Dissociation of hypothalamic effects on ultrasound production and copulation.

Two studies were conducted to compare the brain mechanisms for copulation with those controlling other sexual behaviors, such as the ultrasonic calls that help hamsters and other rodents attract potential mates. Specifically, male and female golden hamsters were castrated and hormone-primed prior to being observed for rates of ultrasound production and levels of sex-typical copulatory behavior (mounts, intromissions and ejaculations in males; lordosis in females). Such tests were conducted before and after subjects received sham operations or bilateral lesions of the preoptic area (POA), anterior hypothalamus (AH) or ventromedial hypothalamus (VMN). The results confirmed previous work in showing the POA lesions decrease rates of intromission, ejaculation and ultrasound production, while VMH lesions decrease lordosis duration. More surprising was the tendency of VMN lesions to increase rates of ultrasonic calling by both males and females. For males, these effects identify differences between the neural circuits controlling copulatory and noncopulatory sexual behaviors. For females, they suggest a mechanism for the behavioral incompatibility of ultrasound production and lordosis. In particular, they raise the possibility that the suspension of ultrasonic calling that normally accompanies lordosis reflects an increase in VMN activity that simultaneously provokes lordosis and inhibits vocalization.

Animals↗
PubMed1993

Photoperiodic and pineal influences on estrogen-stimulated behaviors in female Syrian hamsters.

Three experiments investigated the effects of short photoperiod exposure on the estrogenic facilitation of locomotor activity and lordosis. In Experiment 1, ovariectomized female hamsters were administered exogenous estrogen to stimulate locomotor activity in running wheels. Estrogen was effective in the long photoperiod group but did not stimulate running-wheel activity in the short photoperiod group. In Experiment 2, the role of the pineal gland in mediating photoperiodic influences on female hamster behavior was examined. Both estrogen-induced locomotor activity and estrogen+progesterone-stimulated lordosis behavior were significantly reduced in short photoperiod females. Both these photoperiodic effects were absent in pinealectomized hamsters. Sham-pinealectomized, short photoperiod females expressed behavioral deficits; pinealectomized hamsters in the short photoperiod did not. Experiment 3 investigated lordosis only and used hormone injections rather than silastic implants to administer estrogen. The photoperiodic and pineal effects observed in Experiment 2 were replicated in Experiment 3. Additionally, the suppression of lordosis responsiveness by short photoperiod exposure was estrogen dose dependent. Photoperiodic effects were present when 2 micrograms estradiol cypionate was used but absent when higher estrogen doses were used. These findings are discussed in the context of other results that suggested photoperiodic effects on hamster lordosis were pineal independent.

Animals↗
PubMed1976

Role of monoamines in sexual behavior of the female guinea pig.

Ovariectomized guinea pigs, rendered sexually receptive by injections of estradiol benzoate and progesterone, were treated with drugs that are known to affect monoamine receptor activity. Treatment with the dopamine receptor stimulant apomorphine or the serotonin agonist LSD resulted in a suppression of lordosis behavior that lasted for several hours. The noradrenergic receptor stimulant chlonidine potentiated the performance of lordosis (i.e., increased the duration of individual lordosis responses), while the noradrenergic receptor blocker phenoxybenzamine abolished sexual receptivity. Administration of dopaminergic or serotonergic receptor blockers (pimozide and methysergide, respectively) did not facilitate lordosis. In fact, methysergide produced a brief inhibition of sexual behavior. The results indicate that noradrenergic neurons may be involved in the induction of female sexual behavior in the guinea pig. Dopamine, and possibly serotonin, may serve as transmitters that inhibit lordosis in this species.

Animals↗
PubMed1976

Effect of CNS depressants and stimulants on latency for the appearance of copulatory response in the female rat.

Diethyl ether anesthesia, sodium hexobarbital (20 mg/kg), diphenylhydantoin (50 mg/kg), strychnine (1 mg/kg) and picrotoxin (1-0.25 mg/kg) effectively induced the copulatory response (lordotic behavior) in estradiol benzoate treated ovariectomized rats although no progesterone was given. As none of the tested compounds were effective in replacing progesterone in adrenalectomized animals, adrenal secretion is likely to be implicated in the lordosis activating effect of these compounds. The lordosis response appeared faster after the CNS stimulants than after treatment with the CNS depressants. The influence of diethylether anesthesia, strychnine (0.5 mg/kg) or picrotoxin (0.25 mg/kg) on the latency for the appearance of the lordosis response after IV injection of isopregnenone was studied in estradiol benzoate treated ovariectomized females. A 10 min ether anesthesia delayed the onset of the lordosis response in adrenal intact as well as adrenalectomized animals. Anesthesia given after receptivity had been fully established suppressed the responses for a short period (10-30 min) after the narcosis. The delay of the appearance of the first lordosis response after IV injection of isopregnone exceeded this period. Strychnine but not picrotoxin significantly shortened the latency to the onset of the female copulatory response. It is concluded that the lordotic activating action of progesterone or steroids with progesteronelike ability released from an endogenous source or given IV is influenced by compounds which exert a depressant or stimulant effect on neuronal activity. The total response obtained is not changed but the appearance of the response is prolonged by CNS depressants and shortened by certain CNS stimulants.

20-alpha-Dihydroprogesterone↗