Effect Of EB Research Articles

ヒスタミンＨ１受容体遮断薬Ｅｂａｓｔｉｎｅと血液脳関門のＰ糖タンパク（Ｐ‐ｇｐ）阻害薬であるＶｅｒａｐａｍｉｌとの併用による薬物相互作用に関する臨床薬理試験―断続的眼球運動速度解析を用いた客観的評価による検討―

First-generation antihistamines have an adverse CNS effect such as sedation, whereas second-generation antihistamine drugs are generally non-sedating. The difference in the CNS sedation profile is mainly due to the CNS penetration of the drugs. We hypothesized that the non-sedating profile is caused by low CNS penetration due to regulation by the P-glycoprotein (P-gp) efflux transporter at the blood brain barrier (BBB). A three-way crossover study with more than a 6-day washout period was performed in 8 healthy volunteers. In order to evaluate the drug interaction on P-gp, we used ebastin (Eb) from the second-generation antihistamines and verapamil (Vr) as an inhibitor of P-gp. The three study medication groups were as follows: a single oral dose of Eb 10 mg (E10); a single oral dose of Eb 20 mg (E20); and a single oral dose of Eb 10 mg together with a single oral dose of Vr 80 mg at 3 hours after Eb dosing (EV). The sedative side effect of Eb was measured by both saccadic peak velocity (SPV) analysis, as an objective evaluation, and the visual analogue self-rating scale (VAS), as a subjective evaluation. No sedative effect was observed in any group. These results suggest that Eb has no clinically significant sedative effect even when the Eb dose is increased or with co-administration of P-gp inhibitor.

Abstract 441: Cerebral Vasospasm Depends On Rac-1 Mediated Oxidative Stress

Subarachnoid hemorrhage is one of the most common events related to hypertensive crisis. The cerebral vasospasm is the complication of subarachnoid hemorrhage that causes more frequently death. Experimental evidences describe a direct relationship between hemolysed blood and vasospasm. Understand the molecular basis of vasospasm could help to reduce the mortality in patients with cerebrovascular damage. To clarify this aim, carotid and basilary arteries of rats were mounted on pressure myography and perfused at 100 mmHg. The vessels were placed in intracerebral fluid and entire (eb) or hemolysed blood (hb) was added. Our results showed that the eb did not modify the diameter of the vessel. Meanwhile, hb caused a clear vasoconstriction (max vasoconstriction: 10±1 vs 430±15, p<0.01). Previous studies have hypothesized that oxidative stress could be involved in the cerebral vasospasm. So, the vessels were incubated with Tyron, an antioxidant agent. Our data demonstrated that the administration of Tyron reduced the vasoconstriction induced by hb (max vasoconstriction: 205±7 vs 410±12, p<0.01) without influencing the effect of eb, suggesting an involvement of oxidative stress in the vascular response. Moreover, using lucigenin assay we found an increase in oxidative stress directly in the vessel treated with hb. One of the most important source of oxidative stress is the NADPH oxidase which needs Rac-1 to be activated. Our results demonstrated that the hb, and not the eb, was able to activate Rac-1 in the vessel, evaluated by Rac-1/PAK complex. To clearly define the role of Rac-1 in the vasoconstriction induced by hb, the vessels were transfected with an adenoviral vector containing Rac-1 dominant negative or an empty adenoviral vector. In this experimental condition, the vascular response induced by the hb was significantly blunted as compared to vessels treated with the empty adenovirus (max vasoconstriction: 180±7 vs 390±17, p<0.01). Our results demonstrate that the vasoconstriction induced by the hb is induced by Rac-1-mediated oxidative stress. Thus, Rac-1 could represent the target of novel therapeutic strategies to reduce the cerebral vasospasm and so the mortality in patients with subarachnoid hemorrhage.

Polyaniline for corrosion prevention of mild steel coupled with copper

Polyaniline emeraldine base/epoxy resin (EB/ER) coating was investigated for corrosion protection of mild steel coupled with copper in 3.5% NaCl solution. EB/ER coating with 5–10 wt% EB had long-term corrosion resistance on both uncoupled steel and copper due to the passivation effect of EB on the metal surfaces. During the 150 immersion days, the impedance at 0.1 Hz for the coating increased in the first 1–40 days and subsequently remained constant above 10 9 Ω cm 2, whereas that for pure ER coating fell below 10 6 Ω cm 2 after only 30 or 40 days. Immersion tests on coated steel–copper galvanic couple showed that EB/ER coating offered 100 times more protection than ER coating against steel dissolution and coating delamination on copper, which was mainly attributed to the passive metal oxide films formed by EB blocking both the anodic and cathodic reactions. Salt spray tests showed that 100 μm EB/ER coating protected steel–copper couple for at least 2000 h.

Potentiation of radiation sensitivity in breast tumor cells by the vitamin D3 analogue, EB 1089, through promotion of autophagy and interference with proliferative recovery

1,25-Dihydroxyvitamin D(3) and vitamin D(3) analogues, such as EB 1089, potentiate the response to ionizing radiation in breast tumor cells. The current studies address the basis for this interaction by evaluating DNA damage and repair, the effect of interference with reactive oxygen generation, the involvement of p53 and caspase-3, signaling through c-myc, as well as the induction of senescence and multiple modes of cell death. EB 1089 failed to increase the extent of radiation-induced DNA damage or to attenuate the rate of DNA repair. The reactive oxygen scavengers N-acetyl-l-cysteine and reduced glutathione failed to protect the cells from the promotion of cell death by EB 1089 and radiation. Whereas MCF-7 cells expressing caspase-3 showed significant apoptosis with radiation alone as well as with EB 1089 followed by radiation, EB 1089 maintained its ability to confer susceptibility to radiation-induced cell killing, in large part by interference with proliferative recovery. In contrast, in breast tumor cells lacking p53, where radiation promoted extensive apoptosis and the cells failed to recover after radiation treatment, EB 1089 failed to influence the effect of radiation. EB 1089 treatment interfered with radiation-induced suppression of c-myc; however, induction of c-myc did not prevent senescence by radiation alone or radiation-induced cell death promoted by EB 1089. EB 1089 did not increase the extent of micronucleation, indicative of mitotic catastrophe, induced by radiation alone. However, EB 1089 did promote extensive autophagic cell death in the irradiated cells. Taken together, these studies suggest that the effect of EB 1089 treatment on the radiation response is related in part to enhanced promotion of autophagic cell death and in part to interference with the proliferative recovery that occurs with radiation alone in p53 wild-type breast tumor cells.

X-ray photoelectron spectroscopic analysis of effect of EB on electronic state of Ti species in TiCl4/MgCl2/EB Ziegler-Natta catalysts

X-ray photoelectron spectroscopy (XPS) analysis was performed on TiCl4/MgCl2/EB (ethyl benzoate) catalysts, TiCl4/MgCl2 internal donor free catalysts and TiCl4·EB complex to elucidate the effect of EB on electronic state of Ti species in TiCl4/MgCl2/EB catalysts. Combined with FTIR analysis, the way that EB influenced electronic state of Ti species was postulated. XPS results showed that the binding energy of Ti2p3/2 in TiCl4/MgCl2/EB catalysts was lower than that in TiCl4/MgCl2 internal donor free catalysts indicating that EB influenced electronic state of Ti atoms by providing electrons to Ti atoms in TiCl4/MgCl2/EB catalysts.

Effect of short- vs. long-term estrogen on reinstatement of cocaine-seeking behavior in female rats

Estrogen effects on cocaine-induced reinstatement of lever responding were examined in sham-operated, vehicle-treated (SH + VEH), ovariectomized (OVX + VEH), and OVX female Wistar rats with estrogen replacement (OVX + EB). The effect of long- (64 ± 1.56 days) and short-term (9 days) EB treatment on reinstatement of cocaine-seeking behavior was compared in Experiment 1 and 2, respectively, in order to compare the effect of EB when it was present during the development vs. expression of reinstatement of cocaine-seeking behavior. Rats were trained to self-administer 0.4 mg/kg/inf cocaine. After the acquisition criteria were met, rats continued to respond for cocaine for 2 h/day for a 14-day maintenance period. Cocaine was then replaced with saline and the 21-day extinction period commenced. Subsequently, rats were tested for reinstatement of lever responding on the previously drug-paired lever after alternating daily injections of saline or cocaine. In both experiments, there were no differences between groups in self-administration behavior during training, maintenance, or extinction. In Experiment 1, SH + VEH and chronically treated OVX + EB rats had greater cocaine-induced reinstatement than OVX + VEH rats. In Experiment 2, short-term treated OVX + EB rats also showed enhanced cocaine-induced reinstatement compared to OVX + VEH rats. The results indicate that EB-mediated enhancement of cocaine-induced reinstatement is dependent on EB presence during the expression of reinstatement but not during the formation of stimulus–reward associations during the development of cocaine-reinforced behavior.

Prolonged effects of β-estradiol 3-benzoate on thyroid tumorigenesis in gonadectomized rats pretreated with N-bis(2-hydroxypropyl)nitrosamine

The prolonged modulatory effects of β-estradiol 3-benzoate (EB), a synthetic estrogenic compound, were investigated in a rat two-stage thyroid tumorigenesis model. One week after a single subcutaneous (s.c.) injection of N-bis(2-hydroxypropyl)nitrosamine, gonadectomized F344 rats of both sexes were s.c. implanted with fused pellets containing EB for 32 weeks. Doses of EB at 0, 0.004, 0.02 and 0.1mg were achieved by varying the ratio of EB to cholesterol in the pellet. Major organs including the thyroid, pituitary, liver, kidneys, uterus and brain were weighed and histopathological observation was performed. Serum was assayed for triiodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH). Thyroid weights were increased by the EB pellet implantation in a dose-dependent manner and significantly (P<0.05) elevated in the 0.1mg EB male group and in the 0.02 and 0.1mg EB female groups. The EB treatments dose-dependently suppressed serum T4 levels and inversely elevated serum TSH levels in both sexes but without statistical significance in females. Histopathologically, EB increased the occurrence of thyroid proliferative lesions in males and showed a tendency for increase in females. Interestingly, the effect of EB was more intensive in males than in females, even the lowest dose inducing a follicular carcinoma in a male. These results, thus indicate the possible contribution of prolonged EB stimulation at lower doses to thyroid tumorigenesis without additional promotive condition.

Increased Expression of Mullerian-Inhibiting Substance Correlates with Inhibition of Follicular Growth in the Developing Ovary of Rats Treated with E2 Benzoate

Müllerian-inhibiting substance (MIS) is an essential factor for male sexual differentiation. In the present study, we examined whether the expression of MIS and several of its related transcription factors is altered in the ovaries of rats treated with the synthetic estrogen, E2 benzoate (EB; 10 μg/0.02 ml), from postnatal day 1 (P1) to P5. The EB-treated rats had a significantly reduced number of layered follicles at P6 in comparison with the control rats that were treated with vehicle alone. The expression levels of both MIS mRNA and protein in the granulosa cells of small growing follicles in the ovary at P6 were higher in the EB-treated rats than in the controls. These results indicate that the inhibitory effect of EB on the follicular stratification may correlate with the inappropriately increased expression level of MIS. Furthermore, the expression levels of one of its transcriptional activators, steroidogenic factor 1, and ER-β in granulosa cells of small growing follicles were higher in EB-treated ovaries than in the control ovaries. These results suggest the role of MIS in the regulation of follicular growth and the possible involvement of steroidogenic factor 1and/or ER-β in this molecular cascade may contribute to postnatal ovarian development.

Increased Expression of Müllerian-Inhibiting Substance Correlates with Inhibition of Follicular Growth in the Developing Ovary of Rats Treated with E2 Benzoate

Müllerian-inhibiting substance (MIS) is an essential factor for male sexual differentiation. In the present study, we examined whether the expression of MIS and several of its related transcription factors is altered in the ovaries of rats treated with the synthetic estrogen, E2 benzoate (EB; 10 microg/0.02 ml), from postnatal day 1 (P1) to P5. The EB-treated rats had a significantly reduced number of layered follicles at P6 in comparison with the control rats that were treated with vehicle alone. The expression levels of both MIS mRNA and protein in the granulosa cells of small growing follicles in the ovary at P6 were higher in the EB-treated rats than in the controls. These results indicate that the inhibitory effect of EB on the follicular stratification may correlate with the inappropriately increased expression level of MIS. Furthermore, the expression levels of one of its transcriptional activators, steroidogenic factor 1, and ER-beta in granulosa cells of small growing follicles were higher in EB-treated ovaries than in the control ovaries. These results suggest the role of MIS in the regulation of follicular growth and the possible involvement of steroidogenic factor 1 and/or ER-beta in this molecular cascade may contribute to postnatal ovarian development.

Metabolism of the vitamin D analog EB 1089: Identification of in vivo and in vitro liver metabolites and their biological activities∗

l(S),3(R)-dihydroxy-20(R)-(5′-ethyl-5′-hydroxy-hepta-l′(E),3′(E)-dien-l′-yl)-9,10-secopregna-5(Z),7(E),10(19)-triene (EB 1089) is a novel analog of the vitamin D hormone, calcitriol that has been modified in the side-chain resulting in an increased metabolic stability relative to other side-chain modified analogs (e.g. calcipotriol and 22-oxacalcitriol). To further investigate the metabolism of EB 1089, we set out to study this metabolism both in the rat in vivo as well as in the postmitochondrial liver fractions from rat, man, and minipig in vitro. The same pattern of metabolism was observed in all biological systems employed, both in vivo and in vitro, namely 26- and 26a-hydroxylation of EB 1089. The same metabolites were produced using cultured cell systems (Shankar et al., see this issue). All the possible isomers of 26- and 26a-hydroxy EB 1089 were synthesised and these were compared to biologically generated material using HPLC, NMR, and GC-MS techniques. The predominant natural isomer observed in vitro and in vivo in rats as well as in vitro in humans was identified to be (25S),26R-hydroxy EB 1089. The biological activities of the EB 1089 metabolites on cell growth regulation were 10- to 100-fold lower than that of EB 1089. The effects of the metabolites on calcium metabolism in vivo were comparable to the effect of EB 1089; however, these effects were reduced for the major metabolite in rat and man and for the isomers of 26a-hydroxy EB 1089. We conclude that EB 1089 is metabolised by a different route of side-chain metabolism than calcitriol and that this may explain its relative metabolic stability in pharmacokinetic experiments in vivo compared to that of other vitamin D analogs.

Carbon dioxide diffusion coefficient (Dco2) monitoring during high frequency oscillation of neonates with respiratory distress

The bronchodilator effect of ipratropium bromide (IB) (Atrovent-Sch 1000), 40 μg inhaled, and metaproterenol (Met), 1.25 mg in various combinations, was compared in ten allergic asthmatic patients, aged 23 to 63 years. Six combinations were used at random in a double blind study. The following ventilatory functions—FVC, TGV, SGAW, FEV1, FEF 25-75, V⋅Emax, V⋅E50, V⋅E25, were measured at 30 min. intervals for the first two hours and at 60 minute intervals for the additional three hours. Inhalation of IB followed by Met resulted in additive bronchodilator effect that was significantly greater and longer than EB alone (p<0.05), Met alone (p<0.05), two consecutive inhalations of Met (p<0.05), or Met followed by IB (p<0.05). The bronchodilating effect of EB and Met after five hours was the same as IB after one hour.

Effect of Sodium Poly(styrene sulfonate) on Acid Dyeing of Nylon with C.I. Acid Orange 7.

The effect of sodium poly (styrene sulfonate) (PS) on acid dyeing of nylon with C. I. Orange 7 was investigated. Sodium ethylbenzene sulfonate (EB) was used for comparison. Both of PS and EB is found to be effective as retardant of acid dyeing of nylon. The retarding effect of EB is more remarkable than one of PS. PS is adsorbed only on the surface of nylon due to the large molecular size, while EB is diffused into the nylon substrate. A model of nylon dyeing in the presence of PS or EB is presented.

A flow-cytometer-based micronucleus assay for detection of chromosome aberrations in mice

In our previous study, micronuclei (MN) were induced in bone marrow cells of mice following inhalation exposure to 1300 ppm of 1,3-butadiene (BD) for 6 h per day on 5 consecutive days, and in splenocytes of mice and rats treated intraperitoneally with 80 mg/kg 1,2-epoxybutene (EB) and 30 mg/kg 1,2,3,4-diepoxybutane (DEB), respectively. In the present study, the nature of MN induced by BD, EB and DEB was analyzed by means of fluorescence in situ hybridization (FISH) using mouse minor satellite DNA and rat satellite I DNA as probes. Percentages of MN with centromere signals (MN+) measured following exposures to BD, EB and DEB indicate that these agents are predominantly clastogens. Frequencies of MN+ per 1000 cells suggest that BD, EB and DEB are not only strong clastogens, but also weak aneugens in mice. The weak aneugenic effect of EB and DEB was not observed in rats. Analysis of the number of centromere signals in individual MN, and the size distribution of MN with centromere signals in EB- and DEB-treated animals, and in animals exposed to the positive controls diethylstilbestrol (DES) and mitomycin C (MMC) led to the following conclusions: (1) analysis of MN for the number of centromere signals may be a useful indicator for identifying chemicals with aneugenic properties; (2) there is no correlation between the size of MN and their origin (i.e., chromosome loss/gain or fragment).

Analysis of micronuclei induced by 1,3-butadiene and its metabolites using fluorescence in situ hybridization

In our previous study, micronuclei (MN) were induced in bone marrow cells of mice following inhalation exposure to 1300 ppm of 1,3-butadiene (BD) for 6 h per day on 5 consecutive days, and in splenocytes of mice and rats treated intraperitoneally with 80 mg/kg 1,2-epoxybutene (EB) and 30 mg/kg 1,2,3,4-diepoxybutane (DEB), respectively. In the present study, the nature of MN induced by BD, EB and DEB was analyzed by means of fluorescence in situ hybridization (FISH) using mouse minor satellite DNA and rat satellite I DNA as probes. Percentages of MN with centromere signals (MN +) measured following exposures to BD, EB and DEB indicate that these agents are predominantly clastogens. Frequencies of MN + per 1000 cells suggest that BD, EB and DEB are not only strong clastogens, but also weak aneugens in mice. The weak aneugenic effect of EB and DEB was not observed in rats. Analysis of the number of centromere signals in individual MN, and the size distribution of MN with centromere signals in EB- and DEB-treated animals, and in animals exposed to the positive controls diethylstilbestrol (DES) and mitomycin C (MMC) led to the following conclusions: (1) analysis of MN for the number of centromere signals may be a useful indicator for identifying chemicals with aneugenic properties; (2) there is no correlation between the size of MN and their origin (i.e., chromosome loss/gain or fragment).

Evans Blue Staining Method for Detection of Proteins on Polyacrylamide Gels with Rhodamine B

Abstract A new staining method employing a mixed dye technique is simple, rapid, and sensitive. Solutions of Evans blue (EB, 0.01 %) and rhodamine B (RB, 0.5 %) were mixed up with 1:1 volume ratio. This mixed dye staining method detects as little as 10 ng of bovine serum albumine (BSA). EB is used for protein staining based on its structural similarity to Coomassie brilliant blue R–250 (CB). RB acts as a supplementary agent which inhibits the binding of EB to gel matrix, and so increases the staining effect of EB and enables to achieve cutting down staining/destaining times.

Effect of estradiol on the secretion of LH in the GnRH-pretreated rat after treatment with the GnRH-antagonist, Org 30093.

LH responses induced in the long-term ovariectomized rat by GnRH or GnRH agonistic analogue are augmented by E2. The augmentation by E2 does not occur during, but after termination of GnRH pretreatment. In this study it was investigated whether the augmenting effect of E2 develops also in the GnRH-pretreated rat when the animals were treated with GnRH antagonistic analogue. Two weeks after ovariectomy rats were treated for 10 days with 250 ng GnRH/h (GnRH-rats), released by sc implanted osmotic minipumps. Control rats received a Silastic 'sham pump'. Rats were simultaneously treated with solvent (oil) or estradiol benzoate (EB, 3 micrograms, sc). Each group of rats was divided into two subgroups, one receiving solvent, the other the GnRH antagonist, Org 30093 (ANT, 100 micrograms/injection) on 3 consecutive days. In Experiment 1, the pituitary LH content and the LH secretion following stimulation with the agonistic GnRH analogue buserelin, were measured, in Experiment 2, the plasma concentrations of LH before and after cessation of ANT treatment. The effects of treatment with GnRH, EB and ANT were studied on the basis of 1) the height of the maximal LH response and 2) the half-maximally effective dose (ED50) of buserelin. Experiment 1 revealed that GnRH depleted the pituitary gland to about 42% of its original LH content. In EB-treated GnRH-rats the depletion was even stronger (to 14%). After ANT treatment, the pituitary glands of the GnRH-rats were (partly) repleted (oil: to 65%; EB: to 31%).(ABSTRACT TRUNCATED AT 250 WORDS)

Suppression by LH-releasing hormone (LHRH) of the augmenting effect of estradiol on the secretion of LH and FSH by the rat pituitary gland.

Estradiol sensitizes the pituitary gland for the gonadotropin-releasing activity of LHRH. LHRH desensitizes the pituitary gland and does so in a dose-dependent manner. Moreover, LHRH dose-dependently suppresses the sensitizing effect of EB. In rats with an LHRH concentration in the plasma of about 90 pg/ml, the sensitizing effect of estradiol is absent.

Suppression by LRH of the stimulatory effect of oestradiol on the secretion of LH by the rat pituitary gland.

Ovariectomized rats were infused with varying doses of luteinizing hormone-releasing-hormone (LRH). Some of the rats were also treated with oestradiol benzoate (EB). The effects of these pre-treatments on the in vitro release of luteinizing hormone (LH) were studied. The following parameters of in vitro LH release were measured: the autonomous secretion rate; the secretion rate following maximum stimulation with LRH, and the total quantity of LH released during the 6-hour experiment. The in vivo pre-treatments with LRH and EB dose-dependently decreased the pituitary LH content as well as all three of the above parameters of in vitro LH secretion. There was a linear relationship between the pituitary LH content and the three parameters of in vitro LH release. These parameters were therefore expressed as percentage of the pituitary LH content to give the relative LH secretion rates. The three parameters were thereby corrected for LRH/EB-induced changes in the pituitary LH content. In this way we obtained information on the effects of LRH and EB on the state of the LH release mechanisms of the gonadotropes. EB potentiated the LRH-induced depletion of the pituitary LH stores at all in vivo LRH infusion rates. The effect of EB on the quantity of LH released during perifusion in vitro, however, varied with the previous LRH infusion rates. After LRH infusion rates lower than about 120 ng/h (which establishes plasma concentrations of about 70 ng/l) EB enhanced the stimulated quantity of LH released. After higher rates of LRH infusion, EB lowered the amount of LH released.(ABSTRACT TRUNCATED AT 250 WORDS)

Time-dependent modulation by estrogen of amphetamine-induced hyperactivity in male rats

The effect of estradiol benzoate on the increase in activity induced by d-amphetamine (0.25 mg/kg) was studied in male rats. Both short latency and long latency effects were observed. Amphetamine-induced hyperactivity was increased 45 minutes after estradiol (50 μg/kg) administration, decreased one day later and again increased during the period 8–16 days after injection. At doses of 12.5 and 25 μg/kg, effects were smaller and not statistically significant, although they had a similar temporal pattern to the 50 μg/kg dose. The short-latency, presumably non-genomic, effect of EB was studied in more detail at 15, 30, 45 and 60 minutes after the administration of 50 μg/kg EB. An enhancement of the amphetamine-induced increase in locomotor activity reached its maximum 30 minutes after injection. The time factor was critical for the effects observed, and the results supported the view that estrogen may alter behavior mediated by dopaminergic pathways.

Estradiol and progesterone influence l-5-hydroxytryptophan-induced myoclonus in male guinea pigs: Sex differences in serotonin-steroid interactions

The effects of castration in males and sex differences in the effects of estradiol and progesterone on l-5-hydroxytryptophan ( l-5-HTP)-induced myoclonus in guinea pigs were examined. Castration had no effect on l-5-HTP-induced myoclonus in males. There were sex differences in sensitivity to l-5-HTP. In the absence of steroids, l-5-HTP-induced myoclonus was higher in gonadectomized males than females. A low dose of estradiol benzoate (EB; 3.5 μg) given 46 h before l-5-HTP (100 mg/kg) enhanced myoclonus in gonadectomized females but not males. However, at a higher dose of EB (10 μg) and a lower dose of l-5-HTP (80 mg/kg), myoclonic responding was enhanced in males. These findings indicate that estradiol has a similar effect on l-5-HTP-induced myoclonus in males and females, but do not rule out the possibility of sex differences in sensitivity to l-5-HTP when both sexes are given estradiol priming. When l-5-HTP was given 6 h after 0.5 mg progesterone in estradiol-primed males, myoclonus was enhanced. Progesterone treatment reverses the facilitative effect of EB on l-5-HTP-induced myoclonus in females. Therefore, progesterone has opposite effects on l-5-HTP-induced myoclonus in males and females. These findings were discussed with respect to the interaction of steroids and 5-HT transmission in the regulation of steroid-dependent reproductive behavior.