Contralateral termination of pudendal nerve fibers in the gracile nucleus of the rat

doi:10.1016/0304-3940(85)90293-9

Neuroscience Letters

Volume 62, Issue 1, 20 November 1985, Pages 113-117

https://doi.org/10.1016/0304-3940(85)90293-9 Get rights and content

Abstract

After applying horseradish peroxidase (HRP) unilaterally to central cut end of the pudendal nerve of the rat, transganglionic HRP-labeling of presumed axon terminals was constantly seen in the nucleus gracilis bilaterally with an ipsilateral predominance.

References (5)

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Lumbosacral dorsal root termination in the nucleus gracilis of the cat
Some observations on terminal degeneration in other medullary sensory nuclei
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M.-M. Mesulam
Tetramethyl benzidine for horseradish peroxidase neurohistochemistry: a non-carcinogenic blue reaction-product with superior sensitivity for visualizing neural afferents and efferents
J. Histochem. Cytochem.
(1978)

There are more references available in the full text version of this article.

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The pro-erectile network is activated by stimulation of the penis and dorsal penile nerve, and also by stimulation of the urethra [77]. Sensory information from the penis reaches the spinal cord, as well as the gracile nucleus [78], the brainstem [79], the hypothalamus (medial preoptic area [80] and paraventricular nucleus [81]), the thalamus [82] and the cortex [83]. Whether these areas are only the relays of sensory pathways conveying genital information en route to the cortex, or whether they are the centers of supraspinal reflex pathways remains to be explored.
Penile erection is a vascular event controlled by the autonomic nervous system. The spinal cord contains the autonomic preganglionic neurons that innervate the penile erectile tissue and the pudendal motoneurons that innervate the perineal striated muscles. Sympathetic pathways are anti-erectile, sacral parasympathetic pathways are pro-erectile, and contraction of the perineal striated muscles upon activity of the pudendal nerves improves penile rigidity. Spinal neurons controlling erection are activated by information from peripheral and supraspinal origin. Both peripheral and supraspinal information is capable of either eliciting erection or modulating or inhibiting an erection already present. Sensory information from the genitals is a potent activator of pro-erectile spinal neurons and elicits reflexive erections. Some pre-motor neurons of the medulla, pons and diencephalon project directly onto spinal sympathetic, parasympathetic and pudendal motoneurons. They receive in turn sensory information from the genitals. These spinal projecting pathways release a variety of neurotransmitters, including biogenic amines (serotonin, dopamine, noradrenaline, and adrenaline) and peptides that, through interactions with many receptor subtypes, exert complex effects on the spinal network that controls penile erection. Some supraspinal structures (e.g. the paraventricular nucleus and the medial preoptic area of the hypothalamus, the medial amygdala), whose roles in erection have been demonstrated in animal models, may not project directly onto spinal pro-erectile neurons. They are nevertheless prone to regulate penile erection in more integrated and coordinated responses of the body, as those occurring during sexual behavior. The application of basic and clinical research data to treatment options for erectile dysfunction has recently proved successful. Pro-erectile effects of phosphodiesterase type 5 inhibitors, acting in the penis, and of melanocortin agonists, acting in the brain, illustrate these recent developments.
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Development of projections of primary afferent fibers from the hindlimb to the gracile nucleus: a WGA-HRP study in the rat
1991, Developmental Brain Research
The projection of primary afferent fibers to the gracile nucleus was studied during development. Injections of wheat germ agglutinin-horseradish peroxidase were made into the hindlimb of fetal, postnatal and adult rats. In most cases the sections were alternately stained for wheat germ agglutinin-horseradish peroxidase including counter stain with Neutral red and for acetylcholinesterase. At embryonic day 17 labelled fibers could be traced to the mid-cervical spinal cord but not further rostrally. At embryonic days E18 and E19 labelled fibers penetrate the rostral pole of the nucleus, which does not happen more caudally. At embryonic day E21 the caudal-most pole of the gracile nucleus still is not penetrated by labelled fibers. From postnatal day 1 onwards labelled fibers are found throughout the entire rostrocaudal extent of the gracile nucleus. These results suggest that primary afferent fibers from the hindlimb first grow to the rostral pole of the gracile nucleus and penetrate the rostral pole immediately upon their arrival. During further development more caudal parts of the gracile nucleus are gradually penetrated in a rostrocaudal fashion by primary afferent fibers of the hindlimb.
Somatotopic organization of the dorsal column nuclei in the rat: transganglionic labelling with B-HRP and WGA-HRP
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To analyze the patterns of cutaneous primary afferent fibers projecting to the dorsal column nuclei in the rat, horseradish peroxidase (HRP)-based tracers were injected intracutaneously into a number of discrete regions of the forelimbs and hindlimbs. Three-4 days following the HRP injections, the rats were perfused transcardially; 60 μm transverse sections were cut, and the HRP was reacted using the tetramethyl benzidine method. Comparisons were made of projections following injections with choleragenoid-conjugated horseradish peroxidase (B-HRP) or with wheat-germ agglutinin conjugated to horseradish peroxidase (WGA-HRP). B-HRP and WGA-HRP produced similar patterns of labelling, but B-HRP produced greater intensity of labelling and slightly larger projection areas. In the cuneate nucleus (CN), HRP labelling of primary afferents from small, delimited regions, e.g., from a portion of the skin of a single digit, appeared to be precisely restricted in rostrocaudally oriented columns, with little or no overlap (in the mediolateral and dorsoventral plane) into adjacent regions. With respect to rostrocaudal organization, a region in the CN containing a dense population of cutaneous primary afferent fibers appeared to be similar to the middle, or cluster, region in cats and in raccoons and the pars rotunda in primates. Projection patterns were very consistent from rat to rat, but their somatotopic organization differed from that suggested by electrophysiological studies: cutaneous afferents from forelimb digit 1 projected near the ventral border of the CN; those from digit 5 projected dorsomedially to those from digit 1; the projections from the remaining digits formed a crescent between the projections from digits 1 and 5. In the gracile nucleus, the organization of cutaneous afferent projections from hindlimb digits was more variable and complex than that found in the CN.
Identification of penile inputs to the rat gracile nucleus
2008, American Journal of Physiology - Regulatory Integrative and Comparative Physiology

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Contralateral termination of pudendal nerve fibers in the gracile nucleus of the rat

Abstract

Lumbosacral dorsal root termination in the nucleus gracilis of the cat

Some observations on terminal degeneration in other medullary sensory nuclei

J. Comp. Neurol.

Tetramethyl benzidine for horseradish peroxidase neurohistochemistry: a non-carcinogenic blue reaction-product with superior sensitivity for visualizing neural afferents and efferents

J. Histochem. Cytochem.