Biomedical subjects

William A Truitt

Publications and source records attributed to William A Truitt.

5 recordsLinked to original sources

PubMed2005

Spinal cord control of ejaculation.

Ejaculation is a reflex mediated by a spinal control center, referred to as a spinal ejaculation generator. During intercourse, the spinal ejaculation generator integrates the sensory inputs that are necessary to trigger ejaculation. At the time of ejaculation, it coordinates the sympathetic, parasympathetic, and somatic outflow to induce the two phases of ejaculation, i.e. emission and expulsion. It also provides the brain with signals related to the occurrence of ejaculation. Experimental and clinical data evidenced that these functions were devoted to neurons located in the lumbosacral cord. We recently characterized a population of spinothalamic neurons in the lumbar spinal cord of male rats (LSt cells) that constitutes an integral part of the spinal ejaculation generator. LSt cells send projections to the autonomic nuclei and motoneurons involved in the emission and expulsion phase, and they receive sensory projections from the pelvis. LSt cells are activated with ejaculation, but not following other components of sexual behavior, and lesions of LSt cells completely ablate ejaculatory function. These data support a pivotal role for the LSt cells in the control of ejaculation.

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PubMed2004

Central regulation of ejaculation.

Ejaculation is a reflex mediated by a spinal control center, referred to as a spinal ejaculation generator. This spinal ejaculation generator coordinates sympathetic, parasympathetic and motor outflow to induce the two phases of ejaculation, i.e., emission and expulsion. In addition, the spinal ejaculation generator integrates this outflow with inputs that are related to the summation of sexual activity prior to ejaculation that are required to trigger ejaculation. Recently, a group of spinothalamic neurons in the lumbar spinal cord (LSt cells) were demonstrated to comprise an integral part of the spinal ejaculation generator. Specifically, lesions of LSt cells completely ablate ejaculatory function. Moreover, LSt cells are activated following ejaculation, but not following other components of sexual behavior. Furthermore, based on their relationship with autonomic nuclei, motoneurons and genital sensory inputs, LSt cells are also in the ideal anatomical position to integrate sensory inputs and autonomic and motor outflow. Additionally, the spinal ejaculation generator is under inhibitory and excitatory influence of supraspinal sites, including the nucleus paragigantocellularis (nPGi), the paraventricular nucleus of the hypothalamus (PVN) and the medial preoptic area (MPOA). Finally, sensory information related to ejaculation is processed in the spinal cord and brain, possibly contributing to the rewarding properties of ejaculation. One candidate pathway for relay of ejaculation-related cues consists of LSt cells and their projections to the parvocellular subparafascicular thalamic nucleus. Moreover, neural activation specifically related to ejaculation is observed in the brain and may reflect of processing of ejaculation-related sensory cues.

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PubMed2003

Activation of a subset of lumbar spinothalamic neurons after copulatory behavior in male but not female rats.

The precise pathways that convey copulation-related information to forebrain regions activated during male and female sexual behavior are poorly understood. Previous work from our laboratory and others has demonstrated the existence of a spinothalamic pathway that is a candidate to relay information to these areas. This pathway originates from a population of spinothalamic neurons in the lumbar spinal cord containing several neuropeptides including galanin, located in laminas 7 and 10 of the lumbar segments 3 and 4. To investigate the involvement of these lumbar spinothalamic neurons in conveying copulation-related information, we tested the hypothesis that these cells are activated after ejaculation in male rats and vaginocervical stimulation in female rats. This was assessed using galanin or cholecystokinin as a marker for this subset of spinothalamic neurons and Fos-immunoreactivity as a marker for neuronal activation. The results demonstrated that activation of these spinothalamic neurons is triggered by stimuli associated with ejaculation. Fos induction was specifically associated with ejaculation, because mounts or intromissions did not trigger expression. Moreover, these spinothalamic neurons were not activated by vaginocervical stimulation in female rats. Spinothalamic neurons have generally been associated with signaling pain and temperature information. The present findings demonstrate that a specific subpopulation of spinothalamic neurons signals information associated with ejaculation.

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

PubMed2003

Restraint accentuates the effects of 5-HT2 receptor antagonists and a 5-HT1A receptor agonist on lordosis behavior.

The effect of restraint on lordosis behavior was examined in proestrous and ovariectomized, hormone-primed rats. Restraint durations from 5 to 60 min had no effect on lordosis behavior of proestrous rats. There was also no effect of 5 min restraint on lordosis behavior of ovariectomized rats hormonally primed with 10 microg estradiol benzoate and 500 microg progesterone. However, after intraperitoneal treatment with 1.0 mg/kg ketanserin tartrate (ketanserin), 5 min of restraint significantly reduced lordosis behavior of both groups of rats. The 5-min restraint combined with 0.50 or 0.75 mg/kg ketanserin reduced lordosis to mount (L/M) ratios of ovariectomized rats, while L/M ratios of proestrous rats were inhibited only by the 1.0 mg/kg dose. Increasing the restraint duration (10 or 15 min) reduced the dose of ketanserin necessary to reduce the L/M ratios of proestrous rats. Treatment with the selective serotonin (5-HT)(2C) receptor antagonist, SB206553 (2.5 or 5.0 mg/kg), in combination with 5 min of restraint, also reduced L/M ratios of hormonally primed, ovariectomized rats. The neural sites responsible for ketanserin's additivity with restraint are unknown, but infusion of the drug into the ventromedial nucleus of the hypothalamus (VMN) did not mimic the systemic treatment. However, 5 min of restraint did enhance the effects of VMN infusion with the 5-HT(1A) receptor agonist, 8-OH-DPAT. In contrast, 8-OH-DPAT's systemic potency was not enhanced by restraint. These findings support the hypothesis that a mild stressor increases the lordosis-inhibiting effects of 5-HT(1A) receptor agonists and that 5-HT(2) receptors may protect against such disruption of lordosis behavior.

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PubMed2002

Identification of a potential ejaculation generator in the spinal cord.

We tested the significance of a population of lumbar spinothalamic cells for male sexual behavior in rats. These cells are positioned to relay ejaculation-related signals from reproductive organs to the brain, and they express neurokinin-1 receptors. Ablation of these neurons by the selective toxin SSP-saporin resulted in a complete disruption of ejaculatory behavior. In contrast, other components of sexual behavior remained intact. These results suggest that this population of spinothalamic cells plays a pivotal role in generation of ejaculatory behavior and may be part of a spinal ejaculation generator.

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