Acute effect of an infusion of Montanoa tomentosa on despair-like behavior and activation of oxytocin hypothalamic cells in Wistar rats.

BACKGROUND AND AIM: In Mexican traditional medicine, Montanoa tomentosa (Mt) has been used as a remedy for reproductive impairments and mood swings. In pre-clinical research, both the extract and some of its active metabolites have produced oxytocinergic-like effects on female reproductive organs; however, there are no detailed studies of its effects on mood swing and brain structures. The aim of this study, was to analyze the behavioral effects of acute administration of a Mt infusion on male rats, during the Open Field (OFT) and Forced Swim (FST) Tests, and their association with the activation of oxytocin (OXT) cells, indicated by Fos protein (Fos/OXT) in the paraventricular (PVN) and supraoptic nuclei (SON). EXPERIMENTAL PROCEDURE: 52 adult male Wistar rats were assigned to two conditions; with FST (n = 8), or without (n = 5). Each integrated condition included four groups [Control, Vehicle, Fluoxetine (Flx; 10 mg/kg), and Mt (50 mg/kg), p.o.]. RESULTS AND CONCLUSION: Mt and Flx treatment produced an anti-despair-like effect on the FST, but no significant changes in locomotor activity. Also, the Mt infusion -but not Flx-significantly increased the number of Fos/OXT cells in the PVN and SON, regardless of the condition, compared to the control and vehicle groups. These results show that Mt, but not Flx, produces an anti-despair-like effect that could be associated with the activation of OXT cells in PVN and SON. This study thus contributes to our knowledge of the pharmacological activity of Mt infusions, which could be a natural antidepressant agent with future clinical relevance.

Anxiolytic- and anxiogenic-like effects of Montanoa tomentosa (Asteraceae): Dependence on the endocrine condition.

ETHNOPHARMACOLOGICAL RELEVANCE: Montanoa tomentosa Cerv. (MT) is a native plant from Mexico used in traditional medicine as a remedy for reproductive impairments and relaxing effects. In previous studies, it has been shown that the endocrine state could modify the antianxiety-like actions of anxiolytic compounds. Although women are the primary user of MT, no studies have evaluated the potential impact of the endocrine milieu on its anti-anxiety actions. AIMS OF THE STUDY: Ascertain the antianxiety effects of M. tomentosa in rats with different hormonal conditions, and to analyze the participation of the GABAA receptor in ovariectomized rats treated with MT. MATERIALS AND METHODS: The animal model of anxiety used was the elevated plus-maze (EPM). Rats' endocrine conditions were: a) Low hormone levels (rats in diestrus I and II phases); b) High hormone levels (proestrus/estrus phases); c) No hormones (ovariectomized rats); and d) Rats under progesterone withdrawal (PW). To evaluate the participation of the GABAA receptor in the anxiolytic-like action of MT the antagonist picrotoxin was used. RESULTS: Results showed that MT induced dose-dependent anxiolytic-like actions in rats with low hormone level conditions. Also, MT reduced anxiety-like behavior in female rats under PW, in contrast to diazepam which was ineffective. MT's anxiolytic-like effect was blocked by picrotoxin, suggesting the participation of the GABAA receptor complex. However, increased anxiety-like behavior was observed in rats with a high hormone level condition and low doses of MT. CONCLUSIONS: Beneficial anxiolytic-like actions of MT are observed under low hormone conditions, particularly in the PW challenge (a condition that can be related to a premenstrual period). Furthermore, the participation of the GABAA receptor is evidenced. However, hormonal variations could induce the opposite effects, hence women should be cautious.

Piper auritum Kunth (Piperaceae) improves the sexual performance of sluggish male rats through enhancing ejaculation.

ETHNOPHARMACOLOGICAL RELEVANCE: Piper auritum Kunth is employed as an aphrodisiac in the traditional medicine, but corroborative evidence for such effect is scarce. AIM OF THE STUDY: The pro-sexual effect of an aqueous extract of P. auritum and its possible mechanisms were analyzed in two paradigms of male sexual function. MATERIAL AND METHODS: Effects of an aqueous extract of P. auritum (PA, single administration) were investigated in the fictive ejaculation, and copulatory behavior paradigms in sexually sluggish male rats. WAY 100635 (antagonist of 5-HT1A receptors), atosiban (antagonist of oxytocinergic receptors), L-NAME (inhibitor of the nitric oxide synthase) and baclofen (antagonist of GABAB receptors) were used as pre-treatments in order to investigate the role of different neurotransmitter systems in PA actions. Chemical profile of PA was determined by Gases Chromatography and Ultra Performance Chromatography-Electrospray Ionization-Masses Spectrometry (UPLC-ESI-MS). RESULTS: In males with retarded ejaculation, PA stimulated ejaculatory behavior and recovered electromyographic activity of pelvic musculature participating in seminal emission and ejaculation. All pre-treatments blocked stimulating effects of PA on the fictive ejaculation; additionally WAY 100635 interfered with PA actions on ejaculatory behavior. Safrol, apigenin dimethylether, myristicin, vaccihein A, sakuranin and sakuranetin flavonoids, were main constituents of PA, with possible participation in its pro-sexual effects. CONCLUSIONS: Pro-sexual effects of P. auritum elicited at level of ejaculation were mediated by several neurotransmitter systems, among which serotonin and its 5-HT1A receptors play an important role. Present findings support P. auritum reputation as an aphrodisiac, with potential use in delayed ejaculation disorder.

The Aqueous Crude Extracts of Montanoa frutescens and Montanoa grandiflora Reduce Immobility Faster Than Fluoxetine Through GABAA Receptors in Rats Forced to Swim.

BACKGROUND: Montanoa frutescens and Montanoa grandiflora have been indistinctly used for centuries in traditional Mexican medicine for reproductive impairments, anxiety, and mood disorders. Preclinical studies support their aphrodisiac and anxiolytic properties, but their effects on mood are still unexplored. METHODS: The effects of 25 and 50 mg/kg of M frutescens and M grandiflora extracts were evaluated on days 1, 7, 14, 21, and 28 of treatment, and compared with fluoxetine (1 mg/kg) and Remotiv (7.14 mg/kg) in Wistar rats. The participation of GABAA receptor in the effects produced by the treatments was explored. RESULTS: Montanoa extracts reduced immobility since day 1 of treatment, while fluoxetine and Remotiv required 14 days. The GABAA antagonism blocked the effects of Montanoa extracts, but not of fluoxetine or Remotiv. CONCLUSIONS: Montanoa extracts prevented quickly the stress-induced behaviors in the swimming test through action at the GABAA receptor, exerting a protective effect different to the typical antidepressants drugs.

Aphrodisiac Activity of the Aqueous Crude Extract of Purple Corn ( Zea mays) in Male Rats.

In the present study, the aphrodisiac properties of the purple corn ( Zea mays) in male rats were analyzed. The aqueous crude extract of purple corn (at 25, 50, and 75 mg/kg) was administered to ( a) copulating male rats and ( b) anesthetized and spinal cord transected male rats. Behavioral parameters of copulatory behavior and parameters of the genital motor pattern of ejaculation previous to its inhibition, under the influence of the purple corn extract, are described. Administration of the aqueous crude extract of purple corn significantly facilitates the arousal and execution of male rat sexual behavior without significant influences on the ambulatory behavior. In addition, purple corn extract elicit a significant increase in the number of discharges of the ejaculatory motor patterns and in the total number of genital motor patterns evoked in spinal rats. The present findings show that the aqueous crude extract of purple corn possesses aphrodisiac activity.

Guibourtia tessmannii-induced fictive ejaculation in spinal male rat: involvement of D1, D2-like receptors.

CONTEXT: Guibourtia tessmannii (Caesalpiniaceae) is a plant traditionally used as aphrodisiac. We previously reported the pro-ejaculatory effects of the aqueous and methanol extracts of G. tesmannii in spinal male rat. However, the mechanism underlying such effects has not been elucidated. OBJECTIVE: This study characterizes the dopaminergic sub-type receptors involved in G. tesmannii-induced ejaculation in male Wistar rat. MATERIALS AND METHODS: Urethane-anesthetized spinal male rats were intravenously treated with saline solution (1 mL/kg, control); dopamine (0.1 µmol/kg, reference); aqueous or methanol extracts of G. tesmannii (20 mg/kg) in the absence or presence of haloperidol (0.26 µmol/kg), a nonspecific dopaminergic receptor antagonist, Sch23390 (0.26 µmol/kg), a specific D1-like receptor antagonist or, sulpiride (0.26 µmol/kg), a specific D2-like receptor antagonist. Electromyography of the bulbospongiosus muscles and intraseminal pressure were recorded after urethral, penile and drug stimulations. RESULTS: Urethral and penile stimulations, intravenous injection of dopamine or, aqueous and methanol extracts of G. tesmannii always triggered the expression of rhythmic contraction of the bulbospongiosus muscles with an average mean of 3.33 ± 0.43; 7.83 ± 0.85; 9.80 ± 0.86; 0.83 ± 0.54 and 2.67 ± 0.95 contractions, respectively. The intraseminal pressure was more expressed after urethral and penile stimulations (15.66 ± 1.58 and 13.60 ± 2.40 mmHg, respectively). In rats pretreated with haloperidol, Sch23390 or sulpiride, no ejaculation was recorded after intravenous injection of G. tesmannii extracts or dopamine. DISCUSSION AND CONCLUSION: Guibourtia tesmannii-induced ejaculation requires the integrity of D1 and D2-like receptors. These findings further justify the ethno-medicinal claims of G. tesmannii as an aphrodisiac.

Aphrodisiac activity of Phlegmariurus saururus in copulating and noncopulating male rats.

BACKGROUND: Phlegmariurus saururus is popularly known in Argentina as aphrodisiac. For this reason, it was previously investigated and determined that the decoction of this plant elicits pro-ejaculatory activity and increases the ejaculatory potency in the Fictive Ejaculation Model. HYPOTHESIS/PURPOSE: the decoction of P. saururus facilitates sexual behavior in sexually experienced male rat and induces copulatory behavior in non-copulating male rats. METHODS: The extraction method (decoction) was validated through Selectivity, Accuracy and Precision, by identification of the majority alkaloids, expressed as sauroxine. Male (sexually experienced and noncopulating) and female (receptive) Wistar rats were used to determine sexual behavior. Sildenafil was used as positive control. The following variables were evaluated: Mount Latency, Intromission Latency, Ejaculation Latency, Post Ejaculatory Interval, as well as the Mounts and Intromissions Number. RESULTS: In sexually experienced male rats, P. saururus decoction stimulates sexual arousal and facilitates sexual execution. In noncopulating male rats, this decoction induces copulation with behavioral characteristics similar to sexually experienced animals. CONCLUSION: P. saururus possesses aphrodisiac activity in copulating and noncopulating male rats.

GABAA/benzodiazepine receptor complex mediates the anxiolytic-like effect of Montanoa tomentosa.

ETHNOPHARMACOLOGICAL RELEVANCE: Montanoa tomentosa also named Cihuapatli is a native plant of Mexico that has been used in traditional medicine for the last five centuries mainly as a remedy for reproductive impairments. However, there are reports indicating that this plant was also consumed by Mexican ancient people for its relaxing properties. In order to corroborate this information, the present study was conducted to evaluate the effect of Montanoa tomentosa lyophilisate (MT) on rat׳s anxiety-like behavior and to analyze its mechanism of action. MATERIALS AND METHODS: The anxiolytic-like action of MT (1.5, 3.0, 6.0 and 12.0 mg/kg) was investigated in male Wistar rats tested in three animal models of anxiety: the burying behavior, the elevated plus maze and the hole-board tests. As a positive control, the anti-anxiety effects of different doses of the selective GABAA receptor agonist muscimol were also analyzed. In order to evaluate the participation of the GABAA and oxytocin receptors in the anxiolytic-like actions of MT, the GABAA receptors blockers picrotoxin (0.25 and 0.50 mg/kg), bicuculline (2.0 mg/kg) and flumazenil (5.00 and 10.0 mg/kg), the neurosteroid inhibitor finasteride (50.0 and 100 mg/kg) and the oxytocin receptor antagonist atosiban (0.25 µg) were used. Finally, to evaluate general activity, and motor coordination, the open field and rota-rod tests were used. RESULTS: MT at 3.0 mg/kg showed anxiolytic-like effects in the three anxiety paradigms without affecting reactivity, general motor activity or motor coordination; however, at higher doses sedative effects were observed. Picrotoxin (0.25 and 0.50 mg/kg), flumazenil (10.0 mg/kg) and finasteride (100 mg/kg) antagonized the anxiolytic-like actions of MT in the burying behavior test. In the plus maze and hole-board tests bicuculline (2.0 mg/kg) blocked the effects of the plant as well. Atosiban (0.25 µg) did not antagonize the anxiolytic-like actions of MT. CONCLUSIONS: The results corroborate the anxiolytic-like actions of Montanoa tomentosa and suggest that this effect is mediated through GABAA receptors but not oxytocin receptors.

Delay of ejaculation induced by Bersama engleriana in nicotinamide/streptozotocin-induced type 2 diabetic rats.

OBJECTIVE: To evaluate the effects of aqueous and methanolic extracts of Bersama engleriana (B. engleriana) leaves on the expulsion phase of fictive ejaculation in nicotinamide/streptozotocin-induced type 2 diabetic male rats. METHODS: The electromyographic activity of the bulbospongiosus muscles was recorded in urethane anaesthetized, spinal cord transected rats receiving dopamine (0.1 µmol/L/kg) intravenously, in the absence or presence of aqueous and methanolic extracts of B. engleriana (2.5, 10, 50, 60, 75 mg/kg). In another experiment, the pro-ejaculatory effect of dopamine (0.1 µmol/L/kg, i.v.) was monitored in rats orally pre-treated with the aqueous and methanolic extracts (60 mg/kg) of B. engleriana for 1 or 4 weeks. RESULTS: Results of the study showed that the intravenous administration of B. engleriana did not provoke any contraction of the ejaculatory muscles whilst rhythmic and rapid contractions of the bulbospongiosus muscles accompanied sometimes by penis movement and expulsion of the urethral contents were recorded after dopamine application. The sequential treatment of animals with B. engleriana extracts (2.5-75.0 mg/kg) followed by dopamine (0.1 µmol/L/kg) resulted in a dose-dependent abolishment of the pro-ejaculatory response due to dopamine. However, in animals orally submitted to a daily gavage with B. engleriana extracts (60 mg/kg) for 1 or 4 weeks, the ejaculation stimulating effect of dopamine (0.1 µmol/L/kg) was significantly delayed (P<0.01) but not completely suppressed. CONCLUSIONS: Present findings suggest the involvement of dopaminergic system in the activity of B. engleriana and further support its aphrodisiac potentials due to sterols and saponins revealed in this plant.

Montanoa frutescens and Montanoa grandiflora extracts reduce anxiety-like behavior during the metestrus-diestrus phase of the ovarian cycle in Wistar rats.

In previous studies, the anxiolytic-like effects of Montanoa tomentosa and Montanoa frutescens were reported in male rats, but the potential anxiolytic-like effects of Montanoa plants during the different phases of the ovarian cycle in rats remain to be explored. The anxiolytic-like effects of the aqueous crude extracts of M. frutescens (25 and 50 mg/kg) and M. grandiflora (25 and 50 mg/kg) in the elevated plus maze were investigated in Wistar rats during the estrous cycle and compared with 2 mg/kg diazepam as a reference anxiolytic drug. To investigate any motor effect (i.e., hyperactivity, no changes, or hypoactivity) associated with the treatments, the rats were evaluated in the open field test. The M. frutescens (25 and 50 mg/kg) and M. grandiflora (50 mg/kg) extracts exerted anxiolytic-like effects during the metestrus-diestrus phase, similar to diazepam, without disrupting spontaneous motor activity. No significant effects of the extracts were detected in either behavioral test during the proestrus-estrus phase, whereas diazepam produced motor hypoactivity in the open field test. These results indicate that the M. frutescens and M. grandiflora extracts possess anxiolytic-like effects that depend on the ovarian cycle phase, supporting the Mexican ancient medicinal use of these plants to ameliorate anxiety disorders.

Increase of the ejaculatory potency by the systemic administration of aqueous crude extracts of cihuapatli (Montanoa genus) plants in spinal male rats.

In the present study, evidence on the aphrodisiac activity of Montanoa frutescens and Montanoa grandiflora and a comparison with the aphrodisiac activity of Montanoa tomentosa is presented. By using the fictive ejaculation model in spinal male rats, electromyographic recordings of the genital motor pattern of ejaculation were obtained in the bulbospongiosus muscles and analyzed after the intravenous injection of aqueous crude extracts of Montanoa tomentosa, Montanoa frutescens, and Montanoa grandiflora. Results showed that the systemic administration of the aqueous crude extracts of Montanoa plants elicits a significant increase in the ejaculatory capacity of spinal male rats with very robust ejaculatory motor patterns that included the expression of tonic penile erections and penile movements and the potent expulsion of urethral contents. In conclusion, Montanoa frutescens and Montanoa grandiflora increase the ejaculatory potency with aphrodisiac activity similar to Montanoa tomentosa.

Mondia whitei (Periplocaceae) prevents and Guibourtia tessmannii (Caesalpiniaceae) facilitates fictive ejaculation in spinal male rats.

BACKGROUND: Mondia whitei and Guibourtia tessmannii are used in Cameroon traditional medicine as aphrodisiacs. The present study was undertaken to evaluate the pro-ejaculatory effects of the aqueous and organic solvent extracts of these plants in spinal male rats. METHODS: In spinal cord transected and urethane-anesthetized rats, two electrodes where inserted into the bulbospongiosus muscles and the ejaculatory motor pattern was recorded on a polygraph after urethral and penile stimulations, intravenous injection of saline (0.1 ml/100 g), dopamine (0.1 µM/kg), aqueous and organic solvent plant extracts (20 mg/kg). RESULTS: In all spinal rats, urethral and penile stimulations always induced the ejaculatory motor pattern. Aqueous or hexane extract of Mondia whitei (20 mg/kg) prevented the expression of the ejaculatory motor pattern. The pro-ejaculatory effects of dopamine (0.1 µM/kg) were not abolished in spinal rats pre-treated with Mondia whitei extracts. Aqueous and methanolic stem bark extracts of Guibourtia tessmannii (20 mg/kg) induced fictive ejaculation characterized by rhythmic contractions of the bulbospongiosus muscles followed sometimes with expulsion of seminal plugs. In rats pre-treated with haloperidol (0.26 µM/kg), no ejaculatory motor pattern was recorded after intravenous injection of Guibourtia tessmannii extracts (20 mg/kg). CONCLUSION: These results show that Mondia whitei possesses preventive effects on the expression of fictive ejaculation in spinal male rats, which is not mediated through dopaminergic pathway; on the contrary, the pro-ejaculatory activities of Guibourtia tessmannii require the integrity of dopaminergic system to exert its effects. The present findings further justify the ethno-medicinal claims of Mondia whitei and Guibourtia tessmannii.

The aqueous crude extract of Montanoa frutescens produces anxiolytic-like effects similarly to diazepam in Wistar rats: involvement of GABAA receptor.

ETHNOPHARMACOLOGICAL RELEVANCE: Cihuapatli is the Nahuatl name assigned to some medicinal plants grouped in the genus Montanoa, where Montanoa frutescens (Family: Asteraceae, Tribe: Heliantheae) is included. The crude extract from these plants has been used for centuries in the Mexican traditional medicine as a remedy for reproductive impairments and mood disorders. Experimental studies have systematically corroborated the traditional use of cihuapatli on reproductive impairments and sexual motivation, however, the effect on mood and "nervous" disorders, remains to be explored. MATERIALS AND METHODS: The anxiolytic-like effect of aqueous crude extract of M. frutescens (25, 50 and 75 mg/kg) was investigated in male Wistar rats evaluated in the elevated plus-maze and compared with several doses of diazepam (1, 2 and 4 mg/kg) as a reference anxiolytic drug. Picrotoxin (1 mg/kg), a noncompetitive antagonist of the GABA(A) receptor, was used in experimental procedures to evaluate if this receptor could be involved in the anxiolytic-like effects produced by M. frutescens. To discard hypoactivity, hyperactivity, or no changes associated with treatments, which could interfere with the behavioral activity in the elevated plus-maze, rats were subjected to the open field test. RESULTS: M. frutescens at 50 mg/kg showed anxiolytic-like activity similarly to 2 mg/kg of diazepam, without disrupts in general motor activity. The anxiolytic-like effect of M. frutescens detected in the elevated plus-maze was blocked by picrotoxin, indicating that GABA(A) receptors are involved in the modulation of this effect. CONCLUSIONS: The results corroborate the use of M. frutescens in folk Mexican ethnomedicine as a potential anxiolytic agent and suggest that this effect is mediated by the GABA(A) receptors. Additionally, some sedative effects with high doses of M. frutescens were detected in the present study.

Fluoxetine chronic treatment inhibits male rat sexual behavior by affecting both copulatory behavior and the genital motor pattern of ejaculation.

INTRODUCTION: Selective serotonin reuptake inhibitors (SSRIs) are antidepressants that cause sexual dysfunction. The SSRI fluoxetine (FLX) appears to particularly affect the ejaculatory response. Ejaculation is regulated both at brain and spinal levels. AIM: To study the acute and chronic effects of FLX on male rat copulatory behavior, trying to distinguish between brain and spinal cord FLX-induced changes on the ejaculatory response. METHODS: Sexually experienced male rats were intraperitoneally injected with 5 or 10 mg/kg FLX and tested for sexual behavior during 60 minutes on days 1, 7, and 14 of treatment. After a 2-day drug holiday, the males chronically treated with the high FLX dose were spinalized to record spontaneous and mechanically evoked genital motor patterns of ejaculation (GMPEs). In addition, independent groups were used to evaluate the acute effects of 1, 3, or 10 µg/rat FLX (intravenously) on the GMPE. MAIN OUTCOME MEASURES: Number of ejaculatory series and their parameters; electromyographic recordings of the GMPE in the bulbospongiosus muscles and their parameters. RESULTS: Acute FLX injection slightly affected sexual behavior display and dose-dependently inhibited the expression of the GMPE. Chronic FLX treatment did not inhibit copulation but produced deficits in the parameters related to ejaculation after the high dose. In these animals, the response capacity of the spinal generator of ejaculation (SGE) as well as the number of discharges in the GMPE was decreased as a result of chronic FLX treatment. CONCLUSIONS: Chronic FLX treatment produces inhibitory effects on male rat copulation, particularly on ejaculation, some of which are exerted directly at the SGE.

Evaluation of the excopula ejaculatory potentials of Bersama engleriana in spinal male rats.

The aim of this study was to investigate the effects of Bersama engleriana and its potential mechanism on fictive ejaculation in spinal male rats. The electromyographic activities of the bulbospongiosus muscles were recorded in spinal cord transected and urethane-anesthetized rats treated intravenously with aqueous (100 mg kg(-1)) and methanolic (100 mg kg(-1)) extracts from the dried leaves of B. engleriana in the absence and presence of dopamine (0.1 micromol kg(-1)) or oxytocin (0.5 UI kg(-1)). Mechanical stimulations of the urethra were also carried out 5 min after the sequential treatments. A single intravenous administration of aqueous (100 mg kg(-1)) and methanolic (100 mg kg(-1)) extracts of B. engleriana did not activate fictive ejaculation. The electromyography recorded after the application of the plant extract was similar to that obtained after intravenous saline injection (200 Gl min(-1)) with no contraction of the bulbospongiosus muscles. Dopamine (0.1 micromol kg(-1)) and oxytocin (0.5 UI kg(-1)) induced rapid rhythmic contractions (P < 0.001) of the bulbospongiosus muscles accompanied by penile erection and sometimes with expulsion of the seminal plugs. Pre-treatment of rats with the two plant extracts completely abolished the occurrence of ejaculation induced by dopamine (0.1 micromol kg(-1)) and oxytocin (0.5 UI kg(-1)). Mechanical stimulation of the urethra carried out 5 min after the sequential treatments always induced penile movements and erections. The inhibitory effect of B. engleriana extracts on the expression of fictive ejaculation in spinal male rat is mediated through dopaminergic and oxytocinergic pathways. This prolonged ejaculatory latency caused by B. engleriana could support its potential use in patients with rapid ejaculation.

Participation of endogenous opioids in the inhibition of the spinal generator for ejaculation in rats.

INTRODUCTION: A spinal pattern generator controls the expression of ejaculation. When this ejaculation generator is activated it can be phasically controlled, at a spinal level, by intrinsic mechanisms that eventually lead to the establishment of both short- and long-lasting inhibitory processes. AIM: To evaluate the hypothesis that endogenous opioids participate in the control of ejaculation by exerting an inhibitory influence upon the spinal generator for ejaculation. MAIN OUTCOME MEASURES: Electromyographic recordings of the ejaculatory motor pattern recorded in the bulbospongiosus muscles were obtained as physiological markers of ejaculation. METHODS: By using a model for the study of ejaculation in spinal male rats, we analyze the effects of the intravenous injection of the opioid agonist morphine and the opioid antagonist naloxone on the expression of the ejaculatory motor pattern. In addition, the effect of pre-treatment with systemic naloxone on the establishment of the inhibition of the ejaculatory motor pattern resulting from its repeated sensory-induced elicitation was evaluated. RESULTS: Data obtained show that: (i) the i.v. injection of morphine (1-10 mg/rat) inhibits whereas that of naloxone (1-10 mg/rat) induces the expression of the genital ejaculatory motor pattern; (ii) naloxone pretreatment dose-dependently blocks the inhibitory effects of the high dose of morphine upon the rhythmic motor pattern of ejaculation; (iii) the inhibition of the ejaculatory response induced by repeated urethral stimulation can be delayed, and the ejaculatory capacity augmented, by naloxone injection (10 mg/rat). CONCLUSION: Together, these evidences support the notion that endogenous opioids modulate the activity of the spinal generator for ejaculation by exerting an inhibitory influence.

The spinal pattern generator for ejaculation.

Ejaculation is the physiological process that describes the expulsion of the semen from the urethra. This physiological response is a remarkably sophisticated phenomenon that requires the participation of several stereotyped motor patterns for its expression and when taking place, it starts a constellation of short- and long-lasting physiological and behavioural processes. Little is known about the neural mechanisms accounting for its activation. It has been recently proposed that a central pattern generator located at the spinal level is involved in the control of ejaculation. The aim of this paper is to review the evidence supporting this notion. Thus, the mechanics of ejaculation, its anatomical substrates and innervation are described. Besides, evidence from behavioural, physiological and pharmacological studies that support the existence of an intraspinal rhythm modulating the ejaculatory response are provided. Data are discussed in the context of the physiology of male sexual function.

Pro-ejaculatory effect of the aqueous crude extract of cihuapatli (Montanoa tomentosa) in spinal male rats.

In the present study, the pro-sexual effect of the cihuapatli (Montanoa tomentosa) and its possible pro-ejaculatory properties in spinal male rats were examined. Systemic administration of the aqueous crude extracts of Montanoa tomentosa exerted a pro-ejaculatory effect and produced an increase in the number of discharges in the ejaculatory motor patterns in the spinal rats. The cihuapatli-induced ejaculatory responses included the expression of penile erections and penile movements and the potent expulsion of urethral contents and in some cases the expulsion of seminal plugs. The cihuapatli-induced ejaculatory motor patterns were similar to that obtained after systemic oxytocin. Cihuapatli- and oxytocin-induced ejaculatory motor responses and the penile erections and movements were abolished by the pre-treatment with hexamethonium, a selective oxytocin antagonist. Present data show that the cihuapatli extract acts directly at the spinal system in charge of the expression of the ejaculatory motor patterns and suggest that the aqueous crude extract exerts its aphrodisiacs properties by increasing sexual potency acting as an oxytocic agent.

Evidence for the involvement of a spinal pattern generator in the control of the genital motor pattern of ejaculation.

One of the hypotheses to explain the neural mechanisms underlying rhythmic behaviours suggests that the central nervous system has the intrinsic capacity to produce repetitive, rhythmic output to the muscles involved in the response by means of a neuronal circuit named central pattern generator (CPG). The occurrence of rhythmic motor patterns during ejaculatory behaviour in mammals, which includes the genital motor pattern, has been shown. A CPG might regulate the timing of the repetitive muscular responses that constitute the ejaculatory motor pattern. The objective of the present study was to evidence that a CPG at a spinal level is involved in the expression and pacing of the rhythmic motor pattern generated during ejaculation. To this purpose we used the genital reflex as a model system. Following the general principles for the study of rhythmic motor patterns, the data obtained in the present series of experiments document that: (1) a rhythmic muscular response, the genital motor pattern, is registered during the ejaculatory event (expulsion of the urethral contents); (2) this ejaculatory motor response has similar EMG characteristics in intact and in spinal urethane-anaesthetised male rats; (3) interruption of the afferent inflow (deafferentation) does not disrupt the expression of the ejaculatory motor train; (4) a change in the stimulation interval does not alter the intrinsic pacing of the ejaculatory-like response; and (5) fictive ejaculation can be induced by pharmacological means. Together, this evidence supports the notion that a CPG produces the rhythmic ejaculatory motor pattern registered during fictive ejaculation.