Characterization of bulbospongiosus muscle reflexes activated by urethral distension in male rats

2012 ◽  
Vol 303 (7) ◽  
pp. R737-R747 ◽  
Author(s):  
Masayuki Tanahashi ◽  
Venkateswarlu Karicheti ◽  
Karl B. Thor ◽  
Lesley Marson
Keyword(s):  
Sensory Nerve ◽  
Male Rats ◽  
Intraluminal Pressure ◽  
Urethral Pressure ◽  
Nerve Branch ◽  
Primary Afferent ◽  
Afferent Fibers ◽  
Single Burst ◽  
Primary Afferent Fibers ◽  
Bulbospongiosus Muscle

The urethrogenital reflex (UGR) is used as a surrogate model of the autonomic and somatic nerve and muscle activity that accompanies ejaculation. The UGR is evoked by distension of the urethra and activation of penile afferents. The current study compares two methods of elevating urethral intraluminal pressure in spinalized, anesthetized male Sprague-Dawley rats ( n = 60). The first method, penile extension UGR, involves extracting the penis from the foreskin, so that urethral pressure rises due to a natural anatomical flexure in the penis. The second method, penile clamping UGR, involves penile extension UGR with the addition of clamping of the glans penis. Groups of animals were prepared that either received no additional treatment, surgical shams, or received bilateral nerve cuts (4 nerve cut groups): either the pudendal sensory nerve branch (SbPN), the pelvic nerves, the hypogastric nerves, or all three nerves. Penile clamping UGR was characterized by multiple bursts, monitored by electromyography (EMG) of the bulbospongiosus muscle (BSM) accompanied by elevations in urethral pressure. The penile clamping UGR activity declined across multiple trials and eventually resulted in only a single BSM burst, indicating desensitization. In contrast, the penile extension UGR, without penile clamping, evoked only a single BSM EMG burst that showed no desensitization. Thus, the UGR is composed of two BSM patterns: an initial single burst, termed urethrobulbospongiosus (UBS) reflex and a subsequent multiple bursting pattern (termed ejaculation-like response, ELR) that was only induced with penile clamping urethral occlusion. Transection of the SbPN eliminated the ELR in the penile clamping model, but the single UBS reflex remained in both the clamping and extension models. Pelvic nerve (PelN) transection increased the threshold for inducing BSM activation with both methods of occlusion but actually unmasked an ELR in the penile extension method. Hypogastric nerve (HgN) cuts did not significantly alter any parameter. Transection of all three nerves eliminated BSM activation completely. In conclusion, penile clamping occlusion recruits penile and urethral primary afferent fibers that are necessary for an ELR. Urethral distension without significant penile afferent activation recruits urethral primary afferent fibers carried in either the pelvic or pudendal nerve that are necessary for the single-burst UBS reflex.

scholarly journals Opioid Actions in Primary-Afferent Fibers—Involvement in Analgesia and Anesthesia

2011 ◽  
Vol 4 (2) ◽  
pp. 343-365 ◽  
Author(s):  
Eiichi Kumamoto ◽  
Kotaro Mizuta ◽  
Tsugumi Fujita
Keyword(s):  
Primary Afferent ◽  
Afferent Fibers ◽  
Primary Afferent Fibers

scholarly journals Functional Interactions between Tumor and Peripheral Nerve: Changes in Excitability and Morphology of Primary Afferent Fibers in a Murine Model of Cancer Pain

2001 ◽  
Vol 21 (23) ◽  
pp. 9367-9376 ◽  
Author(s):  
David M. Cain ◽  
Paul W. Wacnik ◽  
Michelle Turner ◽  
Gwen Wendelschafer-Crabb ◽  
William R. Kennedy ◽  
...  
Keyword(s):  
Peripheral Nerve ◽  
Cancer Pain ◽  
Murine Model ◽  
Primary Afferent ◽  
Functional Interactions ◽  
Afferent Fibers ◽  
Primary Afferent Fibers

Ultrastructural Analysis of Ectopic Synaptic Boutons Arising From Peripherally Regenerated Primary Afferent Fibers

1999 ◽  
Vol 81 (4) ◽  
pp. 1636-1644 ◽  
Author(s):  
H. Richard Koerber ◽  
Karoly Mirnics ◽  
Anahid M. Kavookjian ◽  
Alan R. Light
Keyword(s):  
Dorsal Horn ◽  
Sensory Neurons ◽  
Ultrastructural Analysis ◽  
Peripheral Stimulus ◽  
Primary Sensory Neurons ◽  
Superficial Dorsal Horn ◽  
Primary Afferent ◽  
Afferent Fibers ◽  
Primary Afferent Fibers ◽  
Synaptic Boutons

Ultrastructural analysis of ectopic synaptic boutons arising from peripherally regenerated primary afferent fibers. The central axons of peripherally regenerated Aβ primary sensory neurons were impaled in the dorsal columns of α-chloralose-anesthetized cats 9–12 mo after axotomy. The adequate peripheral stimulus was determined, and the afferent fibers intracellularly stimulated while simultaneously recording the resulting cord dorsum potentials (CDPs). Fibers that successfully had reinnervated the skin responded to light tactile stimulation, and evoked CDPs that suggested dorsally located boutons were stained intracellularly with horseradish peroxidase (HRP). Two HRP-stained regenerated Aβ afferent fibers were recovered that supported large numbers of axon collaterals and swellings in laminae I, IIo, and IIi. Sections containing the ectopic collateral fibers and terminals in the superficial dorsal horn were embedded in plastic. Analyses of serial ultrathin sections revealed that ectopic projections from both regenerated fibers supported numerous synaptic boutons filled with clear round vesicles, a few large dense core vesicles (LDCVs) and several mitochondria (>3). All profiles examined in serial sections (19) formed one to three asymmetric axo-dendritic contacts. Unmyelinated portions of ectopic fibers giving rise to en passant and terminal boutons often contained numerous clear round vesicles. Several boutons (47%) received asymmetric contacts from axon terminals containing pleomorphic vesicles. These results strongly suggest that regenerated Aβ fibers activated by light tactile stimuli support functional connections in the superficial dorsal horn that have distinct ultrastructural features. In addition, the appearance of LDCVs suggests that primary sensory neurons are capable of changing their neurochemical phenotype.

Hyperalgesia and sensitization of primary afferent fibers

1990 ◽  
pp. 19-45 ◽  
Author(s):  
Srinivasa N. Raja ◽  
Richard A. Meyer ◽  
James N. Campbell
Keyword(s):  
Primary Afferent ◽  
Afferent Fibers ◽  
Primary Afferent Fibers

Response and receptive-field properties of spinomesencephalic tract cells in the cat

1986 ◽  
Vol 55 (1) ◽  
pp. 76-96 ◽  
Author(s):  
R. P. Yezierski ◽  
R. H. Schwartz
Keyword(s):  
Spinal Cord ◽  
Receptive Field ◽  
Dynamic Range ◽  
Receptive Fields ◽  
The Body ◽  
Noxious Stimulation ◽  
Primary Afferent ◽  
Receptive Field Properties ◽  
Afferent Fibers ◽  
Primary Afferent Fibers

Recordings were made from 90 identified spinomesencephalic tract (SMT) cells in the lumbosacral spinal cord of cats anesthetized with alpha-chloralose and pentobarbital sodium. Recording sites were located in laminae I-VIII. Antidromic stimulation sites were located in different regions of the rostral and caudal midbrain including the periaqueductal gray, midbrain reticular formation, and the deep layers of the superior colliculus. Twelve SMT cells were antidromically activated from more than one midbrain level or from sites in the medial thalamus. The mean conduction velocity for the population of cells sampled was 45.2 +/- 21.4 m/s. Cells were categorized based on their responses to graded intensities of mechanical stimuli and the location of excitatory and/or inhibitory receptive fields. Four major categories of cells were encountered: wide dynamic range (WDR); high threshold (HT); deep/tap; and nonresponsive. WDR and HT cells had excitatory and/or inhibitory receptive fields restricted to the ipsilateral hindlimb or extending to other parts of the body including the tail, forelimbs, and face. Some cells had long afterdischarges following noxious stimulation, whereas others had high rates of background activity that was depressed by nonnoxious and noxious stimuli. Deep/tap cells received convergent input from muscle, joint, or visceral primary afferent fibers. The placement of mechanical lesions at different rostrocaudal levels of the cervical spinal cord provided information related to the spinal trajectory of SMT axons. Six axons were located contralateral to the recording electrode in the ventrolateral/medial or lateral funiculi while two were located in the ventrolateral funiculus of the ipsilateral spinal cord. Stimulation at sites used to antidromically activate SMT cells resulted in the inhibition of background and evoked responses for 22 of 25 cells tested. Inhibitory effects were observed on responses evoked by low/high intensity cutaneous stimuli and by the activation of joint or muscle primary afferent fibers. Based on the response and receptive-field properties of SMT cells it is suggested that the SMT may have an important role in somatosensory mechanisms, particularly those related to nociception.

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