The Effect of Castration on Calcitonin Gene-Related Peptide in Spinal Motor Neurons

Popper, Paul; Micevych, Paul E.

doi:10.1159/000125243

Cited by 61 publications

(18 citation statements)

References 20 publications

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“…The finding that castration produces a decrease in the percentage of CGRPir motoneurons is contradictory to data reported for rats (Popper and Micevych, 1989a), but it is in accordance with reports for house mice (Wagner et al. 1994).…”

Section: Discussionsupporting

confidence: 76%

Motoneurons dorsolateral to the central canal innervate perineal muscles in the mongolian gerbil

Ulibarri

Popper

Micevych

1995

J of Comparative Neurology

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The Mongolian gerbil provides a model in which sexually dimorphic areas in the hypothalamus are correlated with sociosexual behaviors such as scent marking and male copulatory behavior. To extend this model, investigations were conducted to determine whether sexually dimorphic areas existed in the spinal cord that could be relevant to male sexual behavior. The focus of these investigations was the perineal muscles associated with the penis. Therefore, this research identified the spinal motoneurons that innervate the bulbocavernosus, levator ani, anal sphincter, and ischiocavernosus muscles of Mongolian gerbils. The motoneuron pool that innervates the bulbocavernosus, levator ani, and anal sphincter was designated the spinal nucleus of the bulbocavernosus (SNB), as for other species of rodents. The motoneuron pool innervating the ischiocavernosus was identified as the dorsolateral nucleus, again, to be consistent with the designation for other rodents. The motoneurons of the gerbil SNB were distributed dorsolateral to the central canal in the lumbosacral transition zone of the spinal column. These motoneurons are located in the region classically defined as area X of the spinal cord. The number of SNB motoneurons was sexually dimorphic, with male gerbils having about five times as many SNB motoneurons as do female gerbils. The size of SNB motoneurons was also sexually dimorphic. The SNB motoneurons of males were 1.5 times larger than the SNB motoneurons of females. The effects of adult castration on the male SNB were also studied. After castration, the size, but not the number, of SNB motoneurons in males was significantly decreased. This decrease was prevented by testosterone treatment. The percentage of calcitonin gene-related peptide (CGRP)-immunoreactive SNB motoneurons was also affected by adult castration. The percentage of CGRP-immunoreactive motoneurons was significantly decreased after adult castration. Again, this decrease was reversed by testosterone treatment. These findings suggest that the SNB of gerbils is sexually dimorphic and is sensitive to circulating levels of gonadal steroids. The unique placement of the SNB motoneurons suggests that an alternative laminar organizational scheme may be necessary for Mongolian gerbil.

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Section: Discussionsupporting

confidence: 76%

Motoneurons dorsolateral to the central canal innervate perineal muscles in the mongolian gerbil

Ulibarri

Popper

Micevych

1995

J of Comparative Neurology

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“…Alterations in androgen exposure have been reported to alter motoneuronal transcription-translation rates for numerous gene products; examples include structural proteins such as ␤-actin and ␤-tubulin (Matsumoto et al, 1994), synaptic components such as the gap junction protein connexin 32 (Matsumoto et al, 1991), signaling peptides such as CGRP (Popper and Micevych, 1989), and various components of neurotrophin systems such as CNTF receptors (Forger et al, 1998). Androgenic changes in dendritic extent and soma size in the SNB, with their associated changes in synaptic connectivity, attest to the functional importance of the androgenic signal.…”

Section: Discussionmentioning

confidence: 99%

Neuronal Size in the Spinal Nucleus of the Bulbocavernosus: Direct Modulation by Androgen in Rats with Mosaic Androgen Insensitivity

2001

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The motoneurons of the spinal nucleus of the bulbocavernosus (SNB) and its target muscles, the bulbocavernosus and levator ani, form a sexually dimorphic circuit that is developmentally dependent on androgen exposure and exhibits numerous structural and functional changes in response to androgen exposure in adulthood. Castration of male adult rats causes shrinkage of SNB somata, and testosterone replacement reverses this effect, but the site at which androgen is acting to cause this change is undetermined. We exploited the X-chromosome residency of the androgen receptor (AR) gene to generate androgenized female rats that were heterozygous for the testicular feminization mutant (tfm) AR mutation and that, as a consequence of ontogenetic random X-inactivation, expressed a blend of androgen-sensitive wild-type cells and tfm-affected androgen-insensitive cells in the SNB. Chronic testosterone treatment of adult mosaics increased soma sizes only in androgen-competent wild-type SNB cells. The size of tfm-affected SNB somata in the same animals did not differ from the size of either the wild-type or tfm-affected SNB neurons in control mosaics that did not receive androgen treatment in adulthood. Because the muscle targets of the SNB are known to be uniformly androgen-sensitive in tfm mosaics, this mosaic analysis provides unambiguous evidence that androgenic effects on motoneuron soma size are mediated locally in the SNB. It is possible that the neuronal AR plays a permissive role in coordinating the actions of androgen. Key words: mosaic; androgen; spinal nucleus of the bulbocavernosus; tfm mutation; soma size; steroid receptorsMost vertebrate motoneurons possess androgen receptors (ARs) (Pfaff, 1968;Sar and Stumpf, 1977;Kelley, 1986;Simerly et al., 1990), making them attractive models of steroidal effects on neuronal structure and function. The spinal nucleus of the bulbocavernosus (SNB), a cluster of motoneurons located in the dorsomedial aspect of lumbar segments 5 and 6, innervates the sexually dimorphic perineal muscles bulbocavernosus and levator ani (BC/LA), which participate in copulatory behavior. Adult male rats have more and larger SNB motoneurons than do females Arnold, 1980, 1981;Schroder, 1980). A perinatal surge of testosterone (T) in males rescues the BC/LA musculature from involution (Cihak et al., 1970) and inhibits apoptosis in the SNB (Nordeen et al., 1985). Exposing females to exogenous androgens during this critical period permanently masculinizes the SNB-BC/LA system (Breedlove and Arnold, 1983). The SNB critical period developmentally precedes AR expression in SNB cells (Jordan et al., 1991), and systemic androgen can rescue genetically androgen-insensitive SNB motoneurons provided that their BC/LA targets remain androgencompetent (Freeman et al., 1996). Furthermore, androgen is unable to rescue the SNB if the BC/LA muscles are treated with anti-androgen (Fishman and Breedlove, 1992) or extirpated (Kurz et al., 1992), indicating that androgen acts indirectly, via actions in the BC/LA, to rescu...

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“…Furthermore, the expression of several peptides is dramatically altered in spinal cord motoneurons after axotomy (Zhang et al, 1993). Previously, it has been demonstrated that testosterone influences the expression of CGRP in androgendependent motoneurons (Popper & Micevych, 1989).…”

Section: Discussionmentioning

confidence: 99%

Effects of irradiation on neuropeptide expression in rat salivary gland and spinal cord

et al. 1994

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It is well-known that a large number of factors can influence the expression of neuropeptides in the nervous system. In the present study, the effects of unilateral and bilateral irradiation to the rat head and neck on the expression of neuropeptides in the innervation of the submandibular gland and in the ganglionic cells of the submandibular ganglion was examined ten days and six months after treatment. Antisera directed against enkephalin and bombesin and immunohistochemical methods were used. The effects of bilateral irradiation on the staining pattern of various neuropeptides in the cervical spinal cord were also studied. In the submandibular gland and in the submandibular ganglionic cells, there was a markedly increased neuropeptide expression ten days after bilateral treatment, as seen after staining with both antisera used, while no changes occurred after unilateral treatment. Six months after treatment, the pattern of neuropeptide expression in the submandibular gland/ganglion corresponded to that seen in controls. Irradiation did not lead to any changes in the staining pattern of neuropeptides in the spinal cord. The observations show that there is a great complexity in the susceptibility of nervous tissues to radiotherapy with respect to influences on the expression of neuropeptides.

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The Effect of Castration on Calcitonin Gene-Related Peptide in Spinal Motor Neurons

Cited by 61 publications

References 20 publications

Motoneurons dorsolateral to the central canal innervate perineal muscles in the mongolian gerbil

Motoneurons dorsolateral to the central canal innervate perineal muscles in the mongolian gerbil

Neuronal Size in the Spinal Nucleus of the Bulbocavernosus: Direct Modulation by Androgen in Rats with Mosaic Androgen Insensitivity

Effects of irradiation on neuropeptide expression in rat salivary gland and spinal cord

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