PubMed · 15435328
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E AUDISIO. 1950-05-25. [The cecal anus].. https://pubmed.ncbi.nlm.nih.gov/15435328/
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The neurophysiological techniques currently available to evaluate anorectal disorders include concentric needle electromyography (EMG) of the external anal sphincter, anal nerve terminal motor latency (TML) measurement in response to transrectal electrical stimulation or sacral magnetic stimulation, motor evoked potentials (MEPs) of the anal sphincter to transcranial magnetic cortical stimulation, cortical recording of somatosensory evoked potentials (SEPs) to anal nerve stimulation, quantification of electrical or thermal sensory thresholds (QSTs) within the anal canal, sacral anal reflex (SAR) latency measurement in response to pudendal nerve or perianal stimulation, and perianal recording of sympathetic skin responses (SSRs). In most cases, a comprehensive approach using several tests is helpful for diagnosis: needle EMG signs of sphincter denervation or prolonged TML give evidence for anal motor nerve lesion; SEP/QST or SSR abnormalities can suggest sensory or autonomic neuropathy; and in the absence of peripheral nerve disorder, MEPs, SEPs, SSRs, and SARs can assist in demonstrating and localizing spinal or supraspinal disease. Such techniques are complementary to other methods of investigation, such as pelvic floor imaging and anorectal manometry, to establish the diagnosis and guide therapeutic management of neurogenic anorectal disorders.
The aim of this study was to determine the localization of 5-hydroxytryptamine2C (5-HT2C) receptors on the motoneurons innervating the external anal sphincter (EAS) of male rats. Motoneurons were retrogradely labeled after percutaneous intramuscular injection of Fluorogold (FG) into the EAS. Using fluorescent immunohistochemistry, FG-positive EAS motoneurons that were immunoreactive for the 5-HT2C receptor (5-HT2C-IR) were targeted for specific examination with widefield microscopy or confocal laser scanning microscopy with spectral separation. Widefield microscopy revealed distributions of FG-positive EAS motoneurons in the L5-S1 gray matter corresponding to the dorsomedial cell group. 5-HT2C-IR positive cells were distributed in the intermediolateral cell column and the ventral horn. Ventral horn 5-HT2C-IR labeling included the dorsomedial cell group as well as the dorsolateral, ventromedial and ventrolateral areas. Confocal analysis of FG-positive EAS motoneurons and 5-HT2C-IR positive motoneuron profiles adjacent to EAS motoneurons that were not labeled with FG but presumably innervate the bulbospongiosus muscle confirmed that EAS motoneurons were immunopositive for the 5-HT2C receptor. These data suggest that previously identified descending serotonergic immunopositive fibers observed terminating on EAS motoneurons might mediate their input through the activation of 5-HT2C receptors.
Japanese quail are an important model for the discovery of neuroendocrine mechanisms of sexual behavior. In common with most birds and many other vertebrates, there are no genitalia of the mammalian kind (no phallus or vagina). Instead, close contact between the cloacal openings of the male and female is critical for successful mating. Prior research has shown that males produce distinctive rhythmic movements of the foam gland portion of the cloacal sphincter muscle (RCSMs) in response to social stimuli (presentation of a conspecific female or male). These RCSMs enhance the male's fertilization success. Females, unlike males, do not show cloacal sphincter movements to social stimuli (Experiment 1) and female cloacal sphincter muscle activity immediately following copulation does not predict fertilization success (Experiment 2). Females implanted with testosterone propionate (TP), however, show large numbers of male-typical RCSMs in response to social stimuli (Experiment 3). The results of Experiment 3 show that rhythmic movements of the cloacal sphincter muscle shown by TP-treated females are regulated by distal (visual) stimuli and therefore by the brain. They also show that the absence of socially modulated RCSMs in normal females is an activational hormone phenomenon (a sex difference produced by adult hormonal dimorphism), rather than a reflection of prior hormonal organization. These results add to an understanding of the hormonal basis of sex differences in motor mechanisms of sexual behavior in non-mammalian species.