Segmental distribution of afferent neurons innervating the canine testis

Nerve and Glial Cell Expressions in the Testes and Epididymides of Different Age Groups of Cane Rat (Thryonomys swinderianus)

Purpose:

This study was conducted to examine the variations in the expressions of neuronal and glial cell markers in the testes and epididymides of different age groups of cane rat using histochemical and immunohistochemical techniques.

Method:

Thirty (32) healthy domesticated male cane rats were used for this investigation. The rats were divided into four groups (prepubertal [≤4 months], pubertal (>4 ≤12 months), adult (>12 ≤30 months), and aged (>30 months)] of 8 animals each. Subsequent to anesthesia and intracardiac perfusion of the rats with 10% buffered formalin, testes were harvested and preliminary assessment of nervous and glial structures was determined using the Golgi technique. Specific immunolocalization was done using the anti-neurofilament (NF-20) and anti-glial fibrillary acid protein (GFAP) for the expressions of neuronal and astrocyte-like cells, respectively.

Result:

Neuronal and astrocyte-like structures as revealed by the Golgi procedure were demonstrated in the tunica albuginea and interstitium of the testes as well as in the periductal muscle coat and epididymal interstitium of the caput down to the caudal segments. Golgi signal intensities of the expressions in both testes and epididymides increased with age advancement. Immunolocalization of the nerve structures and glial cells tallied with the Golgi results. However, NF signal intensity was significantly higher in the adult relative to others. Similarly, GFAP signal intensity increased with age increment.

Conclusion:

This study has shown that the variation in the expression of neuronal and glial cells in the testis and epididymis of the cane rat could be associated with increased reproductive reproductive activity.

Sources of the porcine testis innervation

This study was carried out on three adult male pigs of the large White Polish breed weighing 110-130 kg each. The animals were anaesthetised and injected with retrograde tracer Fast Blue (FB) into right testis. Three weeks later, the pigs were deeply anaesthetised and perfused transcardially with fixative (4% paraformaldehyde in 0.1 M phosphate buffer pH 7.4). Collected ganglia were cut with freezing microtome into 12-μm-thick sections. The sections were examined under a fluorescent microscope (Zeiss). FB-positive neurones were found in pelvic ganglia (anterior pelvic ganglion) (15.4% of all FB(+) neurones), prevertebral ganglia (caudal mesenteric, testicular, aortico-renal and renal ganglia) (59% of all FB(+) neurones), sympathetic chain ganglia (last four lumbar and first three sacral ganglia) (18.1% of all FB(+) neurones) and dorsal root ganglia (DRG) (first three lumbar and first three sacral ganglia) (7.4% of all FB(+) neurones). The majority of FB-positive nerve cell bodies were observed in ipsilateral ganglia, but they were also found in contralateral ganglia (approximately 85% and 15% respectively). Thus, FB-positive neurones were located in the left prevertebral, sympathetic chain and DRG, but surprisingly, they were absent in left anterior pelvic ganglia.

Immunohistochemical investigations of the autonomous innervation of the cervine testis

The innervation of the cervine testis was studied in 6 roe deers, 7 red deers and 14 fallow deers. The results for the three species are rather similar. With anti-sera to neurofilament (NF) and neuron specific enolase (NSE), all small and large nerve fascicles can be demonstrated, but single fibers are incompletely stained. Immunoreactions against protein gene product-9.5 (PGP-9.5) and GAP-43 (growth-associated protein-43) are better suited to depict the complete innervation pattern. Bundles of the superior spermatic and inferior spermatic nerves reach the testis via three access routes as funicular, mesorchial and caudal nerve contributions. We found no morphological evidence that the nerves in the cervine testis are directly involved in regulating Leydig cell function or seminiferous tubular motility. The majority of the testicular nerves are associated with the testicular arteries, but the musculature in the walls of the venous plexus pampiniformis is also innervated. All vascular nerve fibers represent postjunctional sympathetic axons displaying a strong dopamine-beta-hydroxylase (DBH) activity, mostly co-expressed with neuropeptide Y (NPY). The presence of cholinergic fibers in the testis of the deer is only sporadic and probably of no functional importance. In all three species of deer, a small quantity of myelinated nerve fibers is encountered in spermatic cord and tunica albuginea and regarded as afferent. The viscerosensory quality in the testicular intrinsic innervation is very likely mediated by the CGRP (calcitonin gene-related peptide)-positive fibers that run independently from the testicular vessels and end in the connective tissue of spermatic cord and tunica albuginea. The testis of the red deer contains significantly more VIP (vasoactive intestinal polypeptide)-positive axons than that of roe and fallow deer. The nerve density in the interior of the testicular lobules shows no regional differences, but there are age- and season-related changes that correlate with the developmental and functional state of the seminiferous tubules. Small testes with solid and narrow tubules, as seen in the prepuberal phase and during seasonal reproductive quiescence, are better innervated than large testes with expanded and spermatogenetically active seminiferous tubules.

Identification of differentially expressed genes in dorsal root ganglia following partial sciatic nerve injury

Partial sciatic nerve injury, a model of neuropathic pain, elicits a variety of neurochemical, electrophysiological and neuroanatomical changes in primary sensory neurons. We have used the technique of messenger RNA differential display to identify genes with altered expression in these neurons which may contribute to the development of aberrant sensation following such peripheral nerve damage. This approach identified 14 distinct complementary DNA clones, representing transcripts with increased ipsilateral expression in L4/5 dorsal root ganglia, two weeks after unilateral partial ligation of the rat sciatic nerve. Both Zucker diabetic fatty rats and their lean counterparts were used in this study but none of the transcripts identified showed an induction that was confined to one of the two groups. The majority of the clones did not show significant sequence similarity to previously reported genes and therefore may represent novel messenger RNA sequences or, alternatively, unknown regions of partially characterised messenger RNAs. Two of the clones represented transcripts for the known proteins muscle LIM protein and acidic epididymal glycoprotein, neither of which had previously been associated with expression in the nervous system. Reverse transcriptase-polymerase chain reaction analysis and in situ hybridization confirmed that the messenger RNA expression of both muscle LIM protein and acidic epididymal glycoprotein was induced in an ipsilateral-specific manner. Their localisations, examined with in situ hybridization in L5 dorsal root ganglia, were limited in each case to a sub-population of neuronal profiles. Those neuronal profiles that demonstrated muscle LIM protein hybridization were distributed across the profile size range, whereas the distribution of acidic epididymal glycoprotein-positive profiles appeared to be skewed towards smaller profiles. The induction of muscle LIM protein and acidic epididymal glycoprotein in dorsal root ganglia may play an important functional role in the adaptive response of primary sensory neurons following partial sciatic nerve injury.

Primitivism and plasticity of pain--implication of polymodal receptors

Bio-warning and defense mechanisms play the most fundamental roles in living organisms. From an evolutionary point of view, nociceptive systems are very primitive and are richly provided with humoral signaling mechanisms of aboriginal humoral defense systems, as reflected in the primitive nature of the polymodal receptor, a poorly differentiated sensory receptor signaling nociceptive information. Recent advances in studies on pain have made it possible to explain neural mechanisms of pain systems under physiological conditions and reveal that there is a large gap between physiological and pathological pains. Protracted nociceptive inputs under pathological conditions induce plastic, either functional or structural, alterations in the nociceptive pathways. These plastic changes lead to crosstalk among the neural networks, including circuits related to motor, autonomic, or psychological functions. These plastic changes, once established, persist even after the original pain sources disappear in a memory-like fashion. Thus, it is revealed that chronic pain cannot be treated by blocking pain pathways, which is effective against acute pain, but require treatment from a multidisciplinary perspective.

Coexistence of calcitonin gene-related peptide- and substance P-like immunoreactivity in retrogradely labeled superior spermatic neurons in the dog

The coexistence of calcitonin gene-related peptide (CGRP) and substance P (SP) was determined in primary afferent neurons of the superior spermatic nerve of the dog. Testicular afferent neurons were visualized by retrograde labeling with the fluorescent dye fast blue. CGRP-like immunoreactivity (LI) was found in about 80% of testicular L1 and L2 dorsal root ganglion cells, and 81% of CGRP-positive neurons also contained SP. Conversely, SP-LI was found in 66% of testicular afferents, and 96% of SP-positive neurons simultaneously contained CGRP. Both CGRP- and SP-LI were observed in the whole size range of the testicular afferent neurons. No significant difference in the diameter was detected between CGRP- and SP-positive testicular afferent neurons. In contrast, the diameter of SP-positive cells was significantly smaller than that of CGRP-positive cells in the whole population of dorsal root ganglion (DRG) neurons. Compared to skin and muscle afferents, a larger population of the testicular afferents contain these peptides. This is considered to be one of the characteristic features of visceral afferents. Coexistence of CGRP and SP in testicular afferent neurons suggest a close functional relationship between these two neuropeptides in the sensory nervous system.