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Soma Size (soma + size)

Distribution by Scientific Domains

Life Sciences	83%

Selected Abstracts

Testosterone metabolites differentially maintain adult morphology in a sexually dimorphic neuromuscular system

DEVELOPMENTAL NEUROBIOLOGY, Issue 4 2010
Tom Verhovshek
Abstract The lumbar spinal cord of rats contains the sexually dimorphic, steroid-sensitive spinal nucleus of the bulbocavernosus (SNB). Androgens are necessary for the development of the SNB neuromuscular system, and in adulthood, continue to influence the morphology and function of the motoneurons and their target musculature. However, estrogens are also involved in the development of the SNB system, and are capable of maintaining function in adulthood. In this experiment, we assessed the ability of testosterone metabolites, estrogens and nonaromatizable androgens, to maintain neuromuscular morphology in adulthood. Motoneuron and muscle morphology was assessed in adult normal males, sham-castrated males, castrated males treated with testosterone, dihydrotestosterone, estradiol, or left untreated, and gonadally intact males treated with the 5,-reductase inhibitor finasteride or the aromatase inhibitor fadrozole. After 6 weeks of treatment, SNB motoneurons were retrogradely labeled with cholera toxin-HRP and reconstructed in three dimensions. Castration resulted in reductions in SNB target muscle size, soma size, and dendritic morphology. Testosterone treatment after castration maintained SNB soma size, dendritic morphology, and elevated target muscle size; dihydrotestosterone treatment also maintained SNB dendritic length, but was less effective than testosterone in maintaining both SNB soma size and target muscle weight. Treatment of intact males with finasteride or fadrozole did not alter the morphology of SNB motoneurons or their target muscles. In contrast, estradiol treatment was completely ineffective in preventing castration-induced atrophy of the SNB neuromuscular system. Together, these results suggest that the maintenance of adult motoneuron or muscle morphology is strictly mediated by androgens. © 2009 Wiley Periodicals, Inc. Develop Neurobiol 70: 206,221, 2010. [source]

Differential effects of NT-4, NGF and BDNF on development of neurochemical architecture and cell size regulation in rat visual cortex during the critical period

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2007
Maren Engelhardt
Abstract Development of inhibition is a crucial determinant of the time course of visual cortical plasticity. BDNF strongly affects interneuron development and the onset and closure of the critical period for ocular dominance plasticity. Less is known on the effects of NT-4 despite a clear involvement in ocular dominance plasticity. We have investigated the effects of NT-4 on interneuron development by supplying NT-4 with osmotic minipumps during two time windows overlapping the onset (P12,20) and the peak (P20,28) of the critical period. We assessed the expression of interneuronal markers and soma size maturation either after the end of the infusion periods or at the end of the critical period (P45). We found that NT-4 was very effective in regulating interneuron development. NPY, SOM and PARV neuron somata grew faster during both infusion periods whereas CR neurons only responded during the early infusion period. The effects of soma size elicited during the earlier infusion period were still present at P45. In PARV neurons, NT-4 caused a long-lasting stabilization of CB and NPY expression. Furthermore, NT-4 accelerated the expression of GAD-65 mRNA in a subset of non-PARV neurons of layer V, which normally up-regulate GAD-65 towards the end of the critical period. Most of these effects were shared by NT-4 and BDNF. Some were unexpectedly also shared by NGF, which promoted growth of layer V PARV neurons, stabilized the CB expression and accelerated the GAD-65 expression. The results suggest that neurotrophins act on critical period plasticity by strengthening inhibition. [source]

Thalamic label patterns suggest primary and ventral auditory fields are distinct core regions

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 10 2010
Douglas A. Storace
Abstract A hierarchical scheme proposed by Kaas and colleagues suggests that primate auditory cortex can be divided into core and belt regions based on anatomic connections with thalamus and distinctions among response properties. According to their model, core auditory cortex receives predominantly unimodal sensory input from the ventral nucleus of the medial geniculate body (MGBv); whereas belt cortex receives predominantly cross-modal sensory input from nuclei outside the MGBv. We previously characterized distinct response properties in rat primary (A1) versus ventral auditory field (VAF) cortex; however, it has been unclear whether VAF should be categorized as a core or belt auditory cortex. The current study employed high-resolution functional imaging to map intrinsic metabolic responses to tones and to guide retrograde tracer injections into A1 and VAF. The size and density of retrogradely labeled somas in the medial geniculate body (MGB) were examined as a function of their position along the caudal-to-rostral axis, subdivision of origin, and cortical projection target. A1 and VAF projecting neurons were found in the same subdivisions of the MGB but in rostral and caudal parts, respectively. Less than 3% of the cells projected to both regions. VAF projecting neurons were smaller than A1 projecting neurons located in dorsal (MGBd) and suprageniculate (SG) nuclei. Thus, soma size varied with both caudal-rostral position and cortical target. Finally, the majority (>70%) of A1 and VAF projecting neurons were located in MGBv. These MGB connection profiles suggest that rat auditory cortex, like primate auditory cortex, is made up of multiple distinct core regions. J. Comp. Neurol. 518:1630,1646, 2010. © 2010 Wiley-Liss, Inc. [source]

Neurotrophic effects of GM1 ganglioside and electrical stimulation on cochlear spiral ganglion neurons in cats deafened as neonates

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 6 2007
Patricia A. Leake
Abstract Previous studies have shown that electrical stimulation of the cochlea by a cochlear implant promotes increased survival of spiral ganglion (SG) neurons in animals deafened early in life (Leake et al. [1999] J Comp Neurol 412:543,562). However, electrical stimulation only partially prevents SG degeneration after deafening and other neurotrophic agents that may be used along with an implant are of great interest. GM1 ganglioside is a glycosphingolipid that has been reported to be beneficial in treating stroke, spinal cord injuries, and Alzheimer's disease. GM1 activates trkB signaling and potentiates neurotrophins, and exogenous administration of GM1 has been shown to reduce SG degeneration after hearing loss. In the present study, animals were deafened as neonates and received daily injections of GM1, beginning either at birth or after animals were deafened and continuing until the time of cochlear implantation. GM1-treated and deafened control groups were examined at 7,8 weeks of age; additional GM1 and no-GM1 deafened control groups received a cochlear implant at 7,8 weeks of age and at least 6 months of unilateral electrical stimulation. Electrical stimulation elicited a significant trophic effect in both the GM1 group and the no-GM1 group as compared to the contralateral, nonstimulated ears. The results also demonstrated a modest initial improvement in SG density with GM1 treatment, which was maintained by and additive with the trophic effect of subsequent electrical stimulation. However, in the deafened ears contralateral to the implant SG soma size was severely reduced several months after withdrawal of GM1 in the absence of electrical activation. J. Comp. Neurol. 501:837,853, 2007. © 2007 Wiley-Liss, Inc. [source]

Modulation of sensory neuron potassium conductances by anandamide indicates roles for metabolites

BRITISH JOURNAL OF PHARMACOLOGY, Issue 2 2008
R M Evans
Background and purpose: The endogenous cannabinoid anandamide (AEA) acts at cannabinoid (CB1) and vanilloid (TRPV1) receptors. AEA also shows antinociceptive properties; although the underlying mechanism for this is not fully understood, both CB1 and TRPV1 may be involved. Voltage-activated Ca2+ channels in rat-cultured dorsal root ganglion (DRG) neurons are modulated by AEA. However, AEA in different populations of neurons enhanced or attenuated KCl-evoked Ca2+ influx; these effects were linked with soma size. The aim of this study was to determine how AEA or its metabolites might produce these variable responses. Experimental approach: The whole cell patch-clamp technique and fura-2 Ca2+ imaging were used to characterize the actions of AEA on action potential firing and voltage-activated K+ currents and to determine whether AEA metabolism plays any role in its effects on cultured DRG neurons. Key results: AEA attenuated multiple action potential firing evoked by 300 ms depolarizing current commands in a subpopulation of DRG neurons. Application of 1 ,M AEA attenuated voltage-activated K+ currents and the recovery of KCl-evoked Ca2+ transients. The insensitivity of these responses to the CB1 receptor antagonist rimonabant (100 nM) and preincubation of DRG neurons with pertussis toxin suggested that these actions are not CB1 receptor-mediated. Preincubating DRG neurons with the fatty acid amide hydrolase (FAAH) inhibitor phenylmethylsulphonyl fluoride (PMSF) attenuated the inhibitory actions of AEA on K+ currents and Ca2+ influx. Conclusion and implications: These data suggest that the products of AEA metabolism by FAAH contribute to the attenuation of K+ conductances and altered excitability of cultured sensory neurons. British Journal of Pharmacology (2008) 154, 480,492; doi:10.1038/bjp.2008.93; published online 31 March 2008 [source]