Ejaculation: The emission of SEMEN to the exterior, resulting from the contraction of muscles surrounding the male internal urogenital ducts.Premature Ejaculation: The emission of SEMEN and seminal fluid during the act of preparation for sexual intercourse, i.e. before there is penetration, or shortly after penetration.Copulation: Sexual union of a male and a female in non-human species.Sexual Dysfunction, Physiological: Physiological disturbances in normal sexual performance in either the male or the female.Bulbourethral Glands: Glands situated on each side of the prostate that secrete a fluid component of the seminal fluid into the urethra.Sexual Behavior, Animal: Sexual activities of animals.Sexual Dysfunctions, Psychological: Disturbances in sexual desire and the psychophysiologic changes that characterize the sexual response cycle and cause marked distress and interpersonal difficulty. (APA, DSM-IV, 1994)Semen: The thick, yellowish-white, viscid fluid secretion of male reproductive organs discharged upon ejaculation. In addition to reproductive organ secretions, it contains SPERMATOZOA and their nutrient plasma.Penile Erection: The state of the PENIS when the erectile tissue becomes filled or swollen (tumid) with BLOOD and causes the penis to become rigid and elevated. It is a complex process involving CENTRAL NERVOUS SYSTEM; PERIPHERAL NERVOUS SYSTEMS; HORMONES; SMOOTH MUSCLES; and vascular functions.Nervous System Physiological Processes: Biological actions and events that constitute the functions of the NERVOUS SYSTEM.Orgasm: The climax of sexual excitement in either humans or animals.Masturbation: Sexual stimulation or gratification of the self.Erectile Dysfunction: The inability in the male to have a PENILE ERECTION due to psychological or organ dysfunction.Sperm Motility: Movement characteristics of SPERMATOZOA in a fresh specimen. It is measured as the percentage of sperms that are moving, and as the percentage of sperms with productive flagellar motion such as rapid, linear, and forward progression.Libido: The psychic drive or energy associated with sexual instinct in the broad sense (pleasure and love-object seeking). It may also connote the psychic energy associated with instincts in general that motivate behavior.Seminal Vesicle Secretory Proteins: The secretory proteins of the seminal vesicles are proteins and enzymes that are important in the rapid clotting of the ejaculate. The major clotting protein is seminal vesicle-specific antigen. Many of these seminal vesicle proteins are under androgen regulation, and are substrates for the prostatic enzymes, such as the PROSTATE-SPECIFIC ANTIGEN, a protease and an esterase.Sperm Count: A count of SPERM in the ejaculum, expressed as number per milliliter.Spermatozoa: Mature male germ cells derived from SPERMATIDS. As spermatids move toward the lumen of the SEMINIFEROUS TUBULES, they undergo extensive structural changes including the loss of cytoplasm, condensation of CHROMATIN into the SPERM HEAD, formation of the ACROSOME cap, the SPERM MIDPIECE and the SPERM TAIL that provides motility.Genitalia, Male: The male reproductive organs. They are divided into the external organs (PENIS; SCROTUM;and URETHRA) and the internal organs (TESTIS; EPIDIDYMIS; VAS DEFERENS; SEMINAL VESICLES; EJACULATORY DUCTS; PROSTATE; and BULBOURETHRAL GLANDS).Penis: The external reproductive organ of males. It is composed of a mass of erectile tissue enclosed in three cylindrical fibrous compartments. Two of the three compartments, the corpus cavernosa, are placed side-by-side along the upper part of the organ. The third compartment below, the corpus spongiosum, houses the urethra.Seminal Vesicles: A saclike, glandular diverticulum on each ductus deferens in male vertebrates. It is united with the excretory duct and serves for temporary storage of semen. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Vibration: A continuing periodic change in displacement with respect to a fixed reference. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Sperm Maturation: The maturing process of SPERMATOZOA after leaving the testicular SEMINIFEROUS TUBULES. Maturation in SPERM MOTILITY and FERTILITY takes place in the EPIDIDYMIS as the sperm migrate from caput epididymis to cauda epididymis.Aphrodisiacs: Chemical agents or odors that stimulate sexual desires. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Coitus: The sexual union of a male and a female, a term used for human only.Sperm Agglutination: Agglutination of spermatozoa by antibodies or autoantibodies.Epididymis: The convoluted cordlike structure attached to the posterior of the TESTIS. Epididymis consists of the head (caput), the body (corpus), and the tail (cauda). A network of ducts leaving the testis joins into a common epididymal tubule proper which provides the transport, storage, and maturation of SPERMATOZOA.Midodrine: An ethanolamine derivative that is an adrenergic alpha-1 agonist. It is used as a vasoconstrictor agent in the treatment of HYPOTENSION.Spinothalamic Tracts: A bundle of NERVE FIBERS connecting each posterior horn of the spinal cord to the opposite side of the THALAMUS, carrying information about pain, temperature, and touch. It is one of two major routes by which afferent spinal NERVE FIBERS carrying sensations of somaesthesis are transmitted to the THALAMUS.Hypogastric Plexus: A complex network of nerve fibers in the pelvic region. The hypogastric plexus distributes sympathetic fibers from the lumbar paravertebral ganglia and the aortic plexus, parasympathetic fibers from the pelvic nerve, and visceral afferents. The bilateral pelvic plexus is in its lateral extent.Infertility, Male: The inability of the male to effect FERTILIZATION of an OVUM after a specified period of unprotected intercourse. Male sterility is permanent infertility.Retroperitoneal Space: An area occupying the most posterior aspect of the ABDOMINAL CAVITY. It is bounded laterally by the borders of the quadratus lumborum muscles and extends from the DIAPHRAGM to the brim of the true PELVIS, where it continues as the pelvic extraperitoneal space.Sperm Transport: Passive or active movement of SPERMATOZOA from the testicular SEMINIFEROUS TUBULES through the male reproductive tract as well as within the female reproductive tract.Clomipramine: A tricyclic antidepressant similar to IMIPRAMINE that selectively inhibits the uptake of serotonin in the brain. It is readily absorbed from the gastrointestinal tract and demethylated in the liver to form its primary active metabolite, desmethylclomipramine.Semen Analysis: The quality of SEMEN, an indicator of male fertility, can be determined by semen volume, pH, sperm concentration (SPERM COUNT), total sperm number, sperm viability, sperm vigor (SPERM MOTILITY), normal sperm morphology, ACROSOME integrity, and the concentration of WHITE BLOOD CELLS.Serotonin Uptake Inhibitors: Compounds that specifically inhibit the reuptake of serotonin in the brain.Seminal Plasma Proteins: Proteins found in SEMEN. Major seminal plasma proteins are secretory proteins from the male sex accessory glands, such as the SEMINAL VESICLES and the PROSTATE. They include the seminal vesicle-specific antigen, an ejaculate clotting protein; and the PROSTATE-SPECIFIC ANTIGEN, a protease and an esterase.Fertility: The capacity to conceive or to induce conception. It may refer to either the male or female.p-Chloroamphetamine: Chlorinated analog of AMPHETAMINE. Potent neurotoxin that causes release and eventually depletion of serotonin in the CNS. It is used as a research tool.Prilocaine: A local anesthetic that is similar pharmacologically to LIDOCAINE. Currently, it is used most often for infiltration anesthesia in dentistry.Transurethral Resection of Prostate: Removal of all or part of the PROSTATE, often using a cystoscope and/or resectoscope passed through the URETHRA.Spinal Cord Injuries: Penetrating and non-penetrating injuries to the spinal cord resulting from traumatic external forces (e.g., WOUNDS, GUNSHOT; WHIPLASH INJURIES; etc.).