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Singhal P, Senecal JMM, Senecal JEM, Silwal P, Lynn BD, Nagy JI. Characteristics of Electrical Synapses, C-terminals and Small-conductance Ca 2+ activated Potassium Channels in the Sexually Dimorphic Cremaster Motor Nucleus in Spinal Cord of Mouse and Rat. Neuroscience 2023; 521:58-76. [PMID: 37100373 DOI: 10.1016/j.neuroscience.2023.04.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 03/17/2023] [Accepted: 04/18/2023] [Indexed: 04/28/2023]
Abstract
Sexually dimorphic motoneurons (MNs) located in lower lumbar spinal cord are involved in mating and reproductive behaviours and are known to be coupled by electrical synapses. The cremaster motor nucleus in upper lumbar spinal cord has also been suggested to support physiological processes associated with sexual behaviours in addition to its thermoregulatory and protective role in maintaining testes integrity. Using immunofluorescence approaches, we investigated whether cremaster MNs also exhibit features reflecting their potential for electrical synaptic communication and examined some of their other synaptic characteristics. Both mice and rats displayed punctate immunolabelling of Cx36 associated with cremaster MNs, indicative of gap junction formation. Transgenic mice with enhanced green fluorescent protein (eGFP) reporter for connexin36 expression showed that subpopulations of cremaster MNs in both male and female mice express eGFP, with greater proportions of those in male mice. The eGFP+ MNs within the cremaster nucleus vs. eGFP- MNs inside and outside this nucleus displayed a 5-fold greater density of serotonergic innervation and exhibited a paucity of innervation by C-terminals arising from cholinergic V0c interneurons. All MNs within the cremaster motor nucleus displayed prominent patches of immunolabelling for SK3 (K+) channels around their periphery, suggestive of their identity as slow MNs, many though not all of which were in apposition to C-terminals. The results provide evidence for electrical coupling of a large proportion of cremaster MNs and suggest the existence of two populations of these MNs with possibly differential innervation of their peripheral target muscles serving different functions.
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Affiliation(s)
- P Singhal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - J M M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - J E M Senecal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - P Silwal
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - B D Lynn
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada
| | - J I Nagy
- Department of Physiology and Pathophysiology, Rady Faculty of Health Sciences, Max Rady College of Medicine, University of Manitoba, Winnipeg R3E 0J9, Canada.
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Forger NG. The organizational hypothesis and final common pathways: Sexual differentiation of the spinal cord and peripheral nervous system. Horm Behav 2009; 55:605-10. [PMID: 19446077 PMCID: PMC2703449 DOI: 10.1016/j.yhbeh.2009.03.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 03/11/2009] [Accepted: 03/12/2009] [Indexed: 10/20/2022]
Abstract
In honor of the 50th anniversary of the "organizational hypothesis," this paper reviews work on sexual differentiation of the spinal cord and peripheral nervous system. Topics considered include the spinal nucleus of the bulbocavernosus, the ejaculation center, the cremaster nucleus, sensory and autonomic neurons, and pain. These relatively simple neural systems offer ample confirmation that early exposure to testicular hormones masculinizes the nervous system, including final common pathways. However, I also discuss findings that challenge, or at least stretch, the organizational hypothesis, with important implications for understanding sex differences throughout the nervous system.
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Affiliation(s)
- Nancy G Forger
- Department of Psychology and Center for Neuroendocrine Studies, University of Massachusetts, Amherst MA 01003, USA.
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Payne AP, Mackay S, Ullmann SL, Paris DBPP, Allan GA, McKenzie SK, Gilmore DP. The cremasteric neuromuscular complex in male and female grey short-tailed opossums (Monodelphis domestica). ACTA ZOOL-STOCKHOLM 2006. [DOI: 10.1111/j.1463-6395.2006.00232.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Tanyel FC, Ertunç M, Büyükpamukçu N, Onur R. Mechanisms involved in contractile differences among cremaster muscles according to localization of testis. J Pediatr Surg 2001; 36:1551-60. [PMID: 11584407 DOI: 10.1053/jpsu.2001.27042] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND/PURPOSE Evidence suggests differences in contractility in cremaster muscles (CM) associated with undescended testis caused by alterations of autonomic innervation. Contractile responses of CM to various pharmacologic agents were evaluated and compared according to the localization of testis. METHODS Samples of CM from boys with undescended testis or inguinal hernia were obtained. Twitch and tetanic contractions were recorded isometrically at 37 degrees C. Effects of verapamil, isoprenaline, calcitonin gene-related peptide (CGRP), substance P (SP) and N(omega)-nitro-L-arginine (L-NNA) were investigated. Results were compared through 2-way analysis of variance, and P values less than.05 were considered to be different. RESULTS Verapamil alone significantly (P <.05) decreased contraction amplitudes in CM from both sources; the decrease was more pronounced in CM from boys with inguinal hernia (P <.05). Although isoprenaline increased contraction amplitudes in CM associated with undescended testis (P <.05), CGRP and SP increased contraction amplitudes in CM associated with descended testis (P <.05). L-NNA increased contraction amplitudes in both groups (P <.05). The decrease of contraction amplitudes after verapamil displayed a similar pattern after isoprenaline, SP, and L-NNA. Verapamil-induced contractility decrease was more pronounced after CGRP in both groups (P <.05). CONCLUSIONS Sensitivity of CM to verapamil differs according to localization of testis. Isoprenaline enhances contractility by stimulating Na(+)-K(+)ATPase in undescended testis without altering voltage-sensitive channel sensitivity to verapamil. CGRP and SP increase contractility in inguinal hernia, and CGRP increases the sensitivity of voltage-sensitive Ca(2+) channels to verapamil in CM from both groups. Nitric Oxide (NO) exerts inhibitory action on CM contractility, and it is less pronounced in undescended testis. These differences may contribute to pathophysiology of undescended testis.
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Affiliation(s)
- F C Tanyel
- Department of Pediatric Surgery, Hacettepe University, Medical Center, Ankara, Turkey
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5
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Hutson JM, Hasthorpe S, Heyns CF. Anatomical and functional aspects of testicular descent and cryptorchidism. Endocr Rev 1997; 18:259-80. [PMID: 9101140 DOI: 10.1210/edrv.18.2.0298] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- J M Hutson
- F. Douglas Stephens Surgical Laboratory, Royal Children's Hospital Research Foundation, Parkville, Victoria, Australia
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Barthold JS, Mahler HR, Sziszak TJ, Newton BW. Lack of feminization of the cremaster nucleus by prenatal flutamide administration in the rat and pig. J Urol 1996; 156:767-71. [PMID: 8683779 DOI: 10.1097/00005392-199608001-00057] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
PURPOSE The sexually dimorphic cremaster nucleus contains motoneurons that project via the genitofemoral nerve and theoretically direct androgen dependent testicular descent. The effects of flutamide on descent and masculinization of the cremaster nucleus were studied in the rat and pig. MATERIALS AND METHODS Flutamide was given to pregnant rats and pigs on days 16 to 22 and 65 to 113 of gestation, respectively. Tissues were perfused and examined at birth (pigs) or at age 30 days (rats). Spinal cords were removed, sectioned and immunohistochemically stained for serotonin (rats) or substance P (pigs) to demarcate the position of the cremaster nucleus and allow the determination of cremaster motoneuron number. RESULTS After exposure to flutamide testes were undescended in 6 of 9 rats and 7 of 10 pigs. Cremaster motoneuron number per nucleus were 288 +/- 22 in control versus 250 +/- 27 in flutamide treated rats, and 165 +/- 28 in control versus 148 +/- 24 in flutamide treated pigs. The decrease in motoneuron number by flutamide was significant in both species (p < 0.02) but it did not approach the levels in female rats (93 +/- 11) and pigs (57 +/- 12). Cremaster motoneuron number did not correlate with testicular position. Porcine undescended testes were associated with a significant increase in mean gubernacular volume. CONCLUSIONS Unlike other sexually dimorphic spinal cord nuclei masculinization of the cremaster nucleus appears to be largely androgen independent and it does not correlate with ipsilateral testicular descent. These data suggest that androgens do not mediate descent of the testes via the efferent limb of the genitofemoral nerve.
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Affiliation(s)
- J S Barthold
- Department of Urology, University of Arkansas for Medical Sciences, Little Rock, USA
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7
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Lack of Feminization of the Cremaster Nucleus by Prenatal Flutamide Administration in the Rat and Pig. J Urol 1996. [DOI: 10.1016/s0022-5347(01)65810-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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8
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Moore CL, Dou H, Juraska JM. Number, size, and regional distribution of motor neurons in the dorsolateral and retrodorsolateral nuclei as a function of sex and neonatal stimulation. Dev Psychobiol 1996; 29:303-13. [PMID: 8732805 DOI: 10.1002/(sici)1098-2302(199605)29:4<303::aid-dev1>3.0.co;2-u] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Motor neurons were measured in the retrodorsolateral nucleus (RDLN) and the dorsolateral nucleus (DLN) of adult male and female rats that were reared with normal or reduced levels of maternal anogenital stimulation. In contrast with findings for the spinal nucleus of the bulbocavernosus, which is located in the same spinal segments, reduced stimulation had no effect on neuron number in either nucleus. However, several regional and sex differences were observed. Rostrally located neurons were larger in both the RDLN and the DLN; these location effects were greater in females. There was no sex difference in RDLN neuron size, but DLN neurons were larger in females, particularly in the rostral region. Females had significantly more cells in the RDLN, a nucleus previously considered nondimorphic, whereas males had more DLN neurons. Both regional and sex differences may reflect local differences in trophic factors from targets or afferents.
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Affiliation(s)
- C L Moore
- Department of Psychology, University of Massachusetts, Boston 02125, USA
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Abstract
At present, we believe that descent of the testes within the human is a complex event mediated by both hormonal and mechanical factors. We hypothesize that descent of the testes occurs as a result of the secretion of an androgen-independent factor from a normal testis (descendin). This paracrine factor is responsible for the rapid proliferation (outgrowth) of the ipsilateral gubernaculum. The development of the gubernaculum results in creating a dilated inguinal canal, the width of which matches the testicular width. Descent of the testes through the inguinal canal is an interplay between abdominal pressure, a patent processus vaginalis, and androgen-induced gubernacular regression. We hypothesize that androgens (under control of an intact hypothalamic pituitary axis) alter the viscoelastic properties of the gubernaculum, reducing the turgidity of the gubernaculum and allowing intra-abdominal pressure to push the testis into the scrotum. Cryptorchidism can therefore result when any one or more of the involved factors malfunction.
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Affiliation(s)
- D A Husmann
- Department of Urology, Mayo Clinic, Rochester, Minnesota 55905, USA
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10
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Maternal Contributions to Mammalian Reproductive Development and the Divergence of Males and Females. ADVANCES IN THE STUDY OF BEHAVIOR 1995. [DOI: 10.1016/s0065-3454(08)60392-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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11
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Barthold JS, Mahler HR, Newton BW. Lack of feminization of the cremaster nucleus in cryptorchid androgen insensitive rats. J Urol 1994; 152:2280-6. [PMID: 7966725 DOI: 10.1016/s0022-5347(17)31658-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Androgens may control rat testicular descent via effects on the genitofemoral nerve or cranial gonadal ligaments. Androgen-mediated release of calcitonin gene-related peptide from the genito-femoral nerve (whose motoneuron cell bodies reside in the sexually dimorphic cremaster nucleus) may stimulate cremaster sac formation and testicular descent. Alternatively, androgens may cause regression of cranial gonadal ligaments and thereby allow the testes to descend. To evaluate these theories testicular position, and the cremaster sac and nucleus were studied in Tfm (androgen insensitive) rats. Testes were abdominal, inguinal and scrotal in 20%, 67% and 13% of Tfm male rats, respectively, and cranial ligaments were present in all cases. Mean cremaster nucleus motoneuron number was lower in female rats (70 +/- 14) but not significantly different between normal male (256 +/- 44) and Tfm male (231 +/- 42) rats, and it correlated poorly with testicular position. Calcitonin gene-related peptide immunoreactivity was rarely observed in cremaster motoneurons. These data suggest that the cremaster nucleus is not androgen-dependent, calcitonin gene-related peptide release from cremaster motoneurons is not the likely mechanism of testicular descent and persistent cranial ligaments may cause cryptorchidism in the Tfm rat.
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Affiliation(s)
- J S Barthold
- Department of Urology, University of Arkansas for Medical Sciences, Little Rock
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12
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Oorschot DE. Are you using neuronal densities, synaptic densities or neurochemical densities as your definitive data? There is a better way to go. Prog Neurobiol 1994; 44:233-47. [PMID: 7886226 DOI: 10.1016/0301-0082(94)90040-x] [Citation(s) in RCA: 105] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- D E Oorschot
- Department of Anatomy and Structural Biology, University of Otago, Dunedin, New Zealand
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13
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Cain MP, Kramer SA, Tindall DJ, Husmann DA. Expression of androgen receptor protein within the lumbar spinal cord during ontologic development and following antiandrogen induced cryptorchidism. J Urol 1994; 152:766-9. [PMID: 7912742 DOI: 10.1016/s0022-5347(17)32703-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
One of the leading hypotheses regarding androgenic regulation of testicular descent is that the lumbar genitofemoral nucleus is morphologically altered by testosterone during a specific prenatal period. This hypothesis is based on the unproved assumption that androgen receptor is present in the fetal spinal cord. Using immunohistochemistry we identified androgen receptor in the rat lumbar spinal cord on gestational day 15, a day before the onset of maximal androgenic action for testicular descent. Experiments were performed to determine whether alterations in the morphology of the genitofemoral nucleus are associated with flutamide induced cryptorchidism. Studies revealed a reduction of motoneuron number in rats with flutamide induced cryptorchidism (124.2 +/- 18.9) compared to rats exposed to flutamide without cryptorchidism (269.3 +/- 20.2) and/or male controls (291.0 +/- 14.5, p < 0.01). These findings support the hypothesis that androgens can directly regulate development and morphology of the genitofemoral nucleus.
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Affiliation(s)
- M P Cain
- Department of Urology, Mayo Clinic, Rochester, Minnesota 55905
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14
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Cowburn PJ, Payne AP. Androgens and indoleamines interact to control sexual dimorphisms in the rat spinal cord. Neurosci Lett 1994; 169:101-4. [PMID: 8047261 DOI: 10.1016/0304-3940(94)90366-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Previous studies have shown that (i) androgen administration and (ii) depletion of serotonin can independently masculinise parts of the medial preoptic area and groups of motor neurons in the lumbosacral spinal cord when applied during the early postnatal period. We report here that these two control mechanisms interact in the neonatal female rat. Serotonin depletion by p-chlorophenyl alanine extends the 'critical period' during which androgens can act to stabilise neuron numbers within two sexually dimorphic motor neuron groups in segments L5-S1 (the spinal nucleus of bulbocavernosus and the dorsolateral nucleus), probably by slowing the rate of naturally occurring cell death. A non-dimorphic group of motor neurons (the ventromedial nucleus) was unaffected.
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Affiliation(s)
- P J Cowburn
- Department of Anatomy, Glasgow University, UK
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15
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Husmann DA, Boone TB, McPhaul MJ. Flutamide-induced testicular undescent in the rat is associated with alterations in genitofemoral nerve morphology. J Urol 1994; 151:509-13. [PMID: 7904316 DOI: 10.1016/s0022-5347(17)35003-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Androgen regulation of testicular descent is an established fact. However, the mechanisms by which androgens assert their influence is unknown. One of the leading hypotheses regarding androgenic control of testicular descent is based upon the assumption that testosterone regulates the development of the sexually dimorphic genitofemoral nucleus and nerve (GFN). To investigate whether or not alterations in the genitofemoral nerve are indeed androgen dependent and associated with testicular undescent, we administered flutamide in a time-specific manner to pregnant Sprague-Dawley rats. The GFN of ten animals with unilateral intra-abdominal testicular undescent was compared with the contralateral GFN associated with the descended testicle. Digital microscopic evaluations found that the GFN associated with testicular undescent did express altered morphologic abnormalities. Specifically, the GFN associated with the cryptorchid testicle had significant reductions in the neural diameter (.0169 +/- .0024 mm.2 versus .0275 +/- .0079 mm.2; p < .01), the number of large myelinated fibers per mm.2 (8.4 +/- 3.3 versus 18.8 +/- 5; p < .001) and the number of small myelinated nerve fibers per mm.2 (632 +/- 87.4 versus 1090.7 +/- 104.3; p < .001). These data suggest that testicular undescent in the rat is associated with morphologic alterations in the ipsilateral genitofemoral nerve. The exact mechanism of how these alterations are related to cryptorchidism remains to be elucidated.
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Affiliation(s)
- D A Husmann
- Department of Urology, Mayo Clinic, Rochester, Minnesota 55905
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Goh DW, Momose Y, Middlesworth W, Hutson JM. The relationship among calcitonin gene-related peptide, androgens and gubernacular development in 3 animal models of cryptorchidism. J Urol 1993; 150:574-6. [PMID: 8100863 DOI: 10.1016/s0022-5347(17)35554-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The relationship among calcitonin gene-related peptide (CGRP), a neurotransmitter in the genitofemoral nerve, androgens and gubernacular development was studied using rats treated prenatally with the antiandrogen flutamide and the mutant cryptorchid TS rat. We compared these 2 groups with the testicular feminization mouse with androgen insensitivity. Gubernacula from male TS rats and flutamide-treated rats were maintained in organ culture and examined for contractile response to CGRP. Controls were gubernacula from normal rats and vehicle-treated rats, respectively. TS rat gubernacula have an inhibited contractile response to CGRP, whereas flutamide-treated rat gubernacula have an exaggerated response. A similar exaggerated response to CGRP has previously been demonstrated in testicular feminization mouse gubernacula. These results revealed abnormalities in gubernacular contractile response to CGRP in these cryptorchid animal models, implying that CGRP and gubernacular contractility may have key roles in mediating normal inguinoscrotal testicular descent.
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Affiliation(s)
- D W Goh
- Department of General Surgery, Royal Children's Hospital, Melbourne, Australia
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17
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Spencer JR, Vaughan ED, Imperato-McGinley J. Studies of the hormonal control of postnatal testicular descent in the rat. J Urol 1993; 149:618-23. [PMID: 8437279 DOI: 10.1016/s0022-5347(17)36166-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Dihydrotestosterone is believed to control the transinguinal phase of testicular descent based on hormonal manipulation studies performed in postnatal rats. In the present study, these hormonal manipulation experiments were repeated, and the results were compared with those obtained using the antiandrogens flutamide and cyproterone acetate. 17 beta-estradiol completely blocked testicular descent, but testosterone and dihydrotestosterone were equally effective in reversing this inhibition. Neither flutamide nor cyproterone acetate prevented testicular descent in postnatal rats despite marked peripheral antiandrogenic action. Further analysis of the data revealed a correlation between testicular size and descent. Androgen receptor blockade did not produce a marked reduction in testicular size and consequently did not prevent testicular descent, whereas estradiol alone caused marked testicular atrophy and testicular maldescent. Reduction of the estradiol dosage or concomitant administration of androgens or human chorionic gonadotropin resulted in both increased testicular size and degree of descent. These data suggest that growth of the neonatal rat testis may contribute to its passage into the scrotum.
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Affiliation(s)
- J R Spencer
- James Buchanan Brady Foundation, Department of Surgery, New York Hospital/Cornell University Medical College, New York
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18
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Cowburn PJ, Payne AP. The effects of serotonin manipulation during the postnatal period on the development of sexually dimorphic and non-dimorphic lumbosacral motor neuron groups in the albino Swiss rat. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1992; 66:59-62. [PMID: 1534718 DOI: 10.1016/0165-3806(92)90140-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Serotonin (5-HT) may act during development as a neurotrophic agent. Evidence suggests that sexually dimorphic regions of the mammalian nervous system (which often possess sexually dimorphic patterns of 5-HT innervation) could provide a model for this aspect of 5-HT action. Albino Swiss rat pups were treated with p-chlorophenyl alanine (pCPA, 200 mg/kg) or 5-hydroxytryptophan (5-HTP, 75 mg/kg) for 14 days after birth. As adults, the number of motor neurons in the sexually dimorphic spinal nucleus of bulbocavernosus (SNB) and dorsolateral nucleus (DLN), together with the non-dimorphic ventromedial nucleus (VM) were analysed. Postnatal treatment with 5-HTP had a general effect of increasing motor neuron numbers in all three groups. However, pCPA treatment had a marked and specific effect on SNB neuron numbers, increasing these in both sexes (+250% in females and +60% in males) compared with control animals. The results suggest that the postnatal innervation of ventral horn motor neurons by 5-HT-containing terminals may affect cell death at this time.
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Affiliation(s)
- P J Cowburn
- Department of Anatomy, Glasgow University, UK
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19
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Poulat P, Sandillon F, Marlier L, Rajaofetra N, Oliver C, Privat A. Distribution of thyrotropin-releasing hormone in the rat spinal cord with special reference to sympathetic nuclei: a light- and electron-microscopic immunocytochemical study. JOURNAL OF NEUROCYTOLOGY 1992; 21:157-70. [PMID: 1560252 DOI: 10.1007/bf01194975] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
This paper deals with the distribution of thyrotropin-releasing hormone-like immunoreactivity in the spinal cord of the rat, and particularly in the sympathetic nuclei, at light and electron microscopic levels. In the dorsal horn, the inner part of laminae II and III displayed thin thyrotropin-releasing hormone immunoreactive profiles. Electron microscopy revealed small immunoreactive varicosities which made synaptic contact with small dendrites or dendritic spines. Dense thyrotropin-releasing hormone-like immunoreactivity was observed in all sympathetic nuclei (nucleus intermediolateralis pars fascicularis and principalis, nucleus intercalatus and dorsal commissural nucleus) except the nucleus intercalatus pars ependymalis. Electron microscopy showed many immunoreactive varicosities which were often in synaptic contact with dendrites (proximal or distal), rarely with perikarya and never with axons. Sometimes, the same immunoreactive varicosity made axodendritic contacts with two dendrites and, conversely one dendrite was sometimes synaptically contacted by two or more immunoreactive varicosities. The ventral horn displayed a diffuse thyrotropin-releasing hormone-like immunoreactivity except for the cremaster nucleus (at lumbar level) which was densely outlined by immunoreactive profiles. Occasionally a large cell body in lamina IX (a putative motoneuron) was outlined by immunoreactive profiles but ultrastructural studies revealed very few immunoreactive axosomatic synapses, while immunoreactive symmetrical or asymmetrical axodendritic synapses were observed. The present study clearly confirms the existence of thyrotropin-releasing hormone immunoreactive synapses, thus substantiating the physiological role of this hormone in the spinal cord.
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Affiliation(s)
- P Poulat
- INSERM U-336, Développement, Plasticité et Vieillissement du Système Nerveux, USTL, Montpellier, France
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Cornbrooks EB, Parsons RL. Sexually dimorphic distribution of a galanin-like peptide in the central nervous system of the teleost fish Poecilia latipinna. J Comp Neurol 1991; 304:639-57. [PMID: 1707426 DOI: 10.1002/cne.903040410] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Immunohistochemical techniques were used to visualize areas of the brain and spinal cord containing a galanin-like peptide in the teleost fish, the sailfin molly. Galanin-like immunoreactivity (GAL-LI) in both males and females was identified in neurons in the nucleus preopticus periventricularis, nucleus lateralis tuberis, and nucleus commissuralis. GAL-LI fibers had a comparable distribution in the forebrain, preoptic, hypothalamic, and visceral sensory areas of both sexes. In striking contrast to these areas, the optic tectum, torus semicircularis, brainstem tegmentum, and spinal cord of the male contained much higher levels of GAL-LI than the female. GAL-LI in these dimorphic areas in the female was limited to single fiber bundles in the ventromedial tegmentum and in the trigeminal system. Additionally, a population of neurons in the preoptic nucleus was found to contain GAL-LI in the male only. Sexual dimorphism was especially prominent in the spinal cord, where extensive GAL-LI fibers were found in the male only. These fibers were oriented in the longitudinal plane and confined largely to the gray matter. Comparative studies were performed on the goldfish spinal cord, in which GAL-LI was localized solely in the dorsal horn and exhibited no sexual dimorphism. Further, examination of spinal cord material from neonatal mollies revealed a lack of spinal GAL-LI at this developmental stage. As the extent of GAL-LI in the male molly spinal cord differs from both the goldfish and from that reported for the mammalian spinal cord, and a prominent sexual dimorphism in GAL-LI extends from the diencephalon to the caudal spinal cord, it is suggested that a galanin-like peptide may play a unique, sex-specific role in this species.
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Affiliation(s)
- E B Cornbrooks
- Department of Anatomy and Neurobiology, University of Vermont College of Medicine, Burlington 05405
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Newton BW. Peptidergic innervation of the cremaster nucleus. I. A sexually dimorphic population of substance P-containing intraspinal neurons exists in the substance P pathway to the rat cremaster nucleus. Brain Res 1990; 537:187-96. [PMID: 1707728 DOI: 10.1016/0006-8993(90)90357-h] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The cremaster nucleus (CN) lies in the lumbar spinal cord and is sexually dimorphic: the male CN contains three times as many motoneurons as the female. The substance P (SP) innervation of the CN is also sexually dimorphic with males receiving a very prominent innervation which is greatly diminished in females. These investigations examined SP-containing neurons located in the ventral half of lamina IV and the lateral aspects of laminae V, VII, and IX, in lumbar spinal levels 1,2. SP-containing intraspinal neurons in these laminae are at least three times as numerous in males than females. This provides the first demonstration of a sexually dimorphic population of spinal neurons which is not motor or preganglionic in nature. These SP-containing interneurons are found within, or adjacent to, the SP-containing fibers which constitute the massive SP pathway to the male CN. Processes of these SP-containing neurons were observed to contribute to the formation of the SP pathway to the male CN. The immunohistochemically demonstrable presence of these lumbar 1,2, laminae IV-IX, SP-containing neurons validates former studies which suggested their existence (Gibson et al., Brain Research, 301 (1984) 243-251; Uda et al., Neurosci. Lett., 57 (1985) 185-190).
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Affiliation(s)
- B W Newton
- Department of Anatomy, University of Arkansas for Medical Sciences, Little Rock 72205
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Newton BW, Unger J, Hamill RW. Calcitonin gene-related peptide and somatostatin immunoreactivities in the rat lumbar spinal cord: sexually dimorphic aspects. Neuroscience 1990; 37:471-89. [PMID: 1983471 DOI: 10.1016/0306-4522(90)90415-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The immunohistochemical distribution of calcitonin gene-related peptide and somatostatin in rat lumbar spinal laminae VII-X was investigated using the peroxidase-antiperoxidase technique. Within L1,2 laminae VII and X, calcitonin gene-related peptide and somatostatin fibers demarcate the location of preganglionic sympathetic neurons in a similar fashion in either sex but somatostatin is distributed in a sexually dimorphic manner in the lumbosacral (L5-S2) spinal cord with the male rat containing more somatostatin fibers and neurons than females. Within the ventral horn (lamina IX), calcitonin gene-related peptide has a sexually dimorphic distribution. Calcitonin gene-related peptide varicose fibers are found within the sexually dimorphic male cremaster nucleus but are virtually absent in the female cremaster nucleus. Calcitonin gene-related peptide varicose fibers are nearly absent in the remainder of the male and female lamina IX: this area includes the other two known sexually dimorphic spinal motonuclei: the dorsomedial and dorsolateral nuclei. Virtually all motoneurons in the lumbosacral spinal cord which are not sexually dimorphic contain calcitonin gene-related peptide. However, calcitonin gene-related peptide containing motoneurons have a heterogeneous distribution within sexually dimorphic nuclei. Calcitonin gene-related peptide containing motoneurons within the male and female cremaster nucleus are extremely rare. Some motoneurons within the male and female dorsomedial and dorsolateral nuclei contain calcitonin gene-related peptide with the female dorsomedial and dorsolateral nuclei containing a greater percentage of calcitonin gene-related peptide-containing motoneurons (c. 50%) than males (c. 20%). Somatostatin fibers are preferentially located in sexually dimorphic nuclei of either sex and are distributed in a sexually dimorphic manner within these nuclei with males containing a greater amount of somatostatin fibers than females. The amount of somatostatin immunoreactivity is most dense in the medial aspect of the dorsolateral nucleus, dense in the dorsomedial nucleus, moderate in the cremaster nucleus, and sparse in the lateral portion of the dorsolateral nucleus. In addition, a small column of motoneurons, between the dorsomedial and dorsolateral nuclei at the L5 level, is outlined by somatostatin fibers in females but is absent in males. Somatostatin containing motoneurons were not observed within the lumbar sexually dimorphic nuclei of either sex.
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Affiliation(s)
- B W Newton
- Department of Anatomy, University of Arkansas for Medical Sciences, Little Rock 72205
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Newton BW, Romagnano MA, Hamill RW. The ontogeny of substance P- and serotonin-like immunoreactivities in the sexually dimorphic cremaster nucleus of the rat spinal cord. BRAIN RESEARCH. DEVELOPMENTAL BRAIN RESEARCH 1989; 47:227-42. [PMID: 2472909 DOI: 10.1016/0165-3806(89)90178-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
This study investigates the ontogeny of two transmitter systems which innervate the sexually dimorphic cremaster nucleus (CN). Since these transmitter systems arise from separate extra- and intraspinal sources, their ontological sequences differ. In males, substance P (SP) innervates CN motoneurons on postnatal day (P) 0, while serotonin (5-HT) is first observed on P2. SP reaches a mature innervation pattern on P20, while 5-HT maturation is prolonged to P40-60. It is suggested that part of the reason for the differing rates of development of 5-HT and SP within CN is due to the source of the innervating fibers; 5-HT descends from the brainstem while SP is of intraspinal origin. On P6, the SP innervation of the dorsal processes of the male CN is so advanced that the spinal cord may be 'sexed' according to the male presence, or the female 'absence', of this SP pattern. In developing and adult females, the 5-HT innervation of the CN is greater than the SP innervation. In addition, the 5-HT and SP innervation of the female CN is greater than the surrounding motor columns. Compared to surrounding ventral gray horn motor nuclei, the CN receives a slightly delayed SP and 5-HT innervation and this may be a reflection of the postnatal formation of the cremaster muscle.
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Affiliation(s)
- B W Newton
- Neurology Unit, Monroe Community Hospital, Rochester, NY
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