Our library of drug research abstracts drawn from the medical literature is updated on a regular schedule, and you can be assured that new soma research articles will be listed here shortly after becoming available to us.
Related Sponsors
Medical research on soma
J Neurophysiol. 2008 May 14;
Kress GJ, Dowling MJ, Meeks JP, Mennerick S
Dentate granule neurons give rise to some of the smallest unmyelinated fibers in the mammalian central nervous system, the hippocampal mossy fibers. These neurons are also key regulators of physiological and pathophysiological information flow through the hippocampus. We took a comparative approach to studying mossy fiber action potential initiation and propagation in hippocampal slices from juvenile rats. Dentate granule neurons exhibited axonal action potential initiation significantly more proximal than CA3 pyramidal neurons. This conclusion was suggested by phase plot analysis of somatic action potentials and by local tetrodotoxin application to the axon and somatodendritic compartments. This conclusion was also verified by immunostaining for voltage-gated sodium channel alpha subunits, and by direct dual soma/axonal recordings. Dentate neurons exhibited a significantly higher action potential threshold and slower axonal conduction velocity than CA3 neurons. We conclude that while the electrotonically proximal axon location of action potential initiation allows granule neurons to sensitively detect and integrate synaptic inputs, the neurons are sluggish to initiate and propagate an action potential.
Dynorphin in pro-opiomelanocortin neurons of the hypothalamic arcuate nucleus.
Neuroscience. 2008 Apr 12;
Maolood N, Meister B
Considerable evidence suggests that dynorphin participates in the regulation of energy balance. In this study, we have used immunohistochemistry to investigate in detail the cellular localization of pro-dynorphin (DYN) immunoreactive cell bodies in the mediobasal hypothalamus with special reference to neurons producing orexigenic or anorexigenic transmitters. In colchicine-treated rats, DYN immunoreactivity was demonstrated in many cell bodies of the arcuate nucleus (Arc). Double-labeling revealed that DYN immunoreactivity was present in approximately 30% of pro-opiomelanocortin (POMC) neurons in the ventrolateral Arc as shown by presence of alpha-melanocyte-stimulating hormone (alpha-MSH) and cocaine- and amphetamine-regulated transcript (CART). In contrast, DYN immunoreactivity was not demonstrated in agouti-related peptide (AgRP)- or neuropeptide Y (NPY) -containing neurons in the ventromedial aspect of the Arc. Dynorphin immunoreactivity was also colocalized with the vesicular acetylcholine (ACh) transporter (VAChT; a marker for cholinergic neurons) in the cell soma of Arc POMC neurons. Brainstem POMC neurons in the commissural part of the solitary tract nucleus (NTS) were devoid of DYN immunoreactivity, whereas DYN immunoreactivity was detected in a few NPY-containing NTS neurons and cholinergic DMX neurons. Our results showing presence of DYN together with alpha-MSH in a subpopulation of hypothalamic POMC neurons further point to the neurochemical heterogeneity of hypothalamic POMC neurons. The results suggest a role for DYN in control of energy balance by mediating the effect of peripheral hormones such as leptin and insulin.
Neurobiol Aging. 2008 May 12;
Moloney AM, Griffin RJ, Timmons S, O'Connor R, Ravid R, O'Neill C
Insulin like growth factor-1 receptor (IGF-1R) and insulin receptor (IR) signalling control vital growth, survival and metabolic functions in the brain. Here we describe specific and significant alterations in IGF-1R, IR, and their key substrate adaptor proteins IRS-1 and IRS-2 in Alzheimer's disease (AD). Western immunoblot analysis detected increased IGF-1R levels, and decreased levels of IGF-1-binding protein-2 (IGFBP-2), a major IGF-1-binding protein, in AD temporal cortex. Increased IGF-1R was observed surrounding and within amyloid-beta (Abeta)-containing plaques, also evident in an animal model of AD, and in astrocytes in AD. However, despite the overall increase in IGF-1R levels, a significantly lower number of neurons expressed IGF-1R in AD, and IGF-1R was aberrantly distributed in AD neurons especially evident in those with neurofibrillary tangles (NFTs). IR protein levels were similar in AD and control cases, however, the IR was concentrated intracellularly in AD neurons, unlike its distribution throughout the neuronal cell soma and in dendrites in control brain. Significant decreases in IRS-1 and IRS-2 levels were identified in AD neurons, in association with increased levels of inactivated phospho(Ser312)IRS-1 and phospho(Ser616)IRS-1, where increased levels of these phosphoserine epitopes colocalised strongly with NFTs. Our results show that IGF-1R and IR signalling is compromised in AD neurons and suggest that neurons that degenerate in AD may be resistant to IGF-1R/IR signalling.
Action potential initiation and propagation: Upstream influences on neurotransmission.
Neuroscience. 2008 Mar 19;
Kress GJ, Mennerick S
Axonal action potentials initiate the cycle of synaptic communication that is key to our understanding of nervous system functioning. The field has accumulated vast knowledge of the signature action potential waveform, firing patterns, and underlying channel properties of many cell types, but in most cases this information comes from somatic intracellular/whole-cell recordings, which necessarily measure a mixture of the currents compartmentalized in the soma, dendrites, and axon. Because the axon in many neuron types appears to be the site of lowest threshold for action potential initiation, the channel constellation in the axon is of particular interest. However, the axon is more experimentally inaccessible than the soma or dendrites. Recent studies have developed and applied single-fiber extracellular recording, direct intracellular recording, and optical recording techniques from axons toward understanding the behavior of the axonal action potential. We are starting to understand better how specific channels and other cellular properties shape action potential threshold, waveform, and timing: key elements contributing to downstream transmitter release. From this increased scrutiny emerges a theme of axons with more computational power than in traditional conceptualizations.
Silencing the cochlear amplifier by immobilizing prestin.
Neuron. 2008 May 8; 58(3): 299-301
Müller U, Gillespie P
Achieving the exquisite sensitivity and frequency selectivity of the mammalian ear requires active amplification of input sound. In this issue of Neuron, Dallos and colleagues demonstrate that the molecular motor prestin, which drives shape changes in the soma of mechanosensory hair cells, underlies mechanical feedback mechanisms for sound amplification in mammals.
J Neurosci. 2008 May 7; 28(19): 5029-39
Vander Jagt TA, Connor JA, Shuttleworth CW
Excessive Ca(2+) loading is central to most hypotheses of excitotoxic neuronal damage. We examined dendritic Ca(2+) signals in single CA1 neurons, injected with fluorescent indicators, after extended exposures to a low concentration of NMDA (5 microM). As shown previously, NMDA produces an initial transient Ca(2+) elevation of several micromolar, followed by recovery to submicromolar levels. Then after a delay of approximately 20-40 min, a large Ca(2+) elevation appears in apical dendrites and propagates to the soma. We show here that this large delayed Ca(2+) increase is required for ultimate loss of membrane integrity. However, transient removal of extracellular Ca(2+) for varying epochs before and after NMDA exposure does not delay the propagation of these events. In contrast to compound Ca(2+) elevations, intracellular Na(+) elevations are monophasic and were promptly reversed by the NMDA receptor antagonist MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate]. MK-801 applied after the transient Ca(2+) elevations blocked the delayed propagating Ca(2+) increase. Even if applied after the propagating response was visualized, MK-801 restored resting Ca(2+) levels. Propagating Ca(2+) increases in dendrites were delayed or prevented by (1) reducing extracellular Na(+), (2) injecting ATP together with the Ca(2+) indicator, or (3) provision of exogenous pyruvate. These results show that extended NMDA exposure initiates degenerative signaling generally in apical dendrites. Although very high Ca(2+) levels can report the progression of these responses, Ca(2+) itself may not be required for the propagation of degenerative signaling along dendrites. In contrast, metabolic consequences of sustained Na(+) elevations may lead to failure of ionic homeostasis in dendrites and precede Ca(2+)-dependent cellular compromise.
High-Dose Carisoprodol During Pregnancy and Lactation (June).
Ann Pharmacother. 2008 May 6;
Briggs GG, Ambrose PJ, Nageotte MP, Padilla G
OBJECTIVE: To report a case of use of high-dose carisoprodol during pregnancy and breast-feeding. CASE SUMMARY: A 28-year-old woman with severe back muscle spasm took carisoprodol 2800 mg/day before and throughout an uncomplicated pregnancy and while exclusively breast-feeding her infant during the first month after birth. Serum drug concentrations of carisoprodol and the active metabolite meprobamate were measured in the mother and infant. Concentrations of these agents also were measured in breast milk. Developmental toxicity was not observed in the near-term infant, whose birth weight was at the 10th percentile for gestational age. Only slight sedation was noted in the infant during breast-feeding, and no signs or symptoms of withdrawal were noted when nursing was stopped. DISCUSSION: Carisoprodol and meprobamate are excreted into breast milk. Although the published human pregnancy data are limited to 15 cases, carisoprodol does not appear to cause developmental toxicity (growth restriction, structural anomalies, functional/neurobehavioral deficits, or death), even when the mother is taking high doses. No signs or symptoms of withdrawal were noted in our infant or in a previously published case when breast-feeding was stopped. Long-term follow-up has not been conducted in exposed infants, and the possibility of functional/neurobehavioral l deficits appearing later in life cannot be excluded. CONCLUSIONS: Except for mild sedation, no other toxicity was observed in a near-term infant exposed to carisoprodol throughout gestation and during breastfeeding in the first month after birth.
J Endocrinol. 2008 May 6;
Tapia-Gonzalez S, Carrero P, Pernia O, Garcia-Segura L, Diz-Chaves Y
It has been previously reported that the neuroprotective hormone oestradiol reduces microglia inflammatory activity. The objective of this study was to test whether two selective oestrogen receptor modulators, tamoxifen and raloxifene, modulate in vivo the activation of microglia induced by the peripheral administration of lipopolysaccharide. Activation of microglia was assessed in the white matter of the cerebellum using immunoreactivity for Major Histocompatability Complex-II. Oestradiol, tamoxifen and raloxifene decreased microglia activation induced by lipopolysaccharide in male and ovariectomized female rats, although the doses of oestradiol that were effective in decreasing microglia reactivity were not the same in both sexes. Tamoxifen reduced microglia activation in all experimental groups at all doses tested (0.5-2 mg/Kg. b.w.) while raloxifene loosed its anti-inflammatory activity at the higher dose tested (2 mg/Kg b.w.). In addition raloxifene had per se a moderate pro-inflammatory activity in the brain of control female rats and its anti-inflammatory activity was partially impaired in female animals after 1 month of deprivation of ovarian hormones. Spots of oestrogen receptor alpha immunoreactivity were detected in the soma and cell processes of microglia. Treatment with lipopolysaccharide, oestradiol or tamoxifen induced an increase of oestrogen receptor alpha immunoreactive spots in the perikaryon of microglia, while oestradiol antagonized the effect of lipopolysaccharide. The results indicate that some oestrogenic compounds decrease brain inflammation by a mechanism that may involve oestrogen receptors expressed by microglia. The findings support the potential therapeutic role of oestrogenic compounds as protective anti-inflammatory agents for the central nervous system.
Are there alternatives to the use of quinine to treat nocturnal leg cramps?
Consult Pharm. 2008 Feb; 23(2): 141-56
Guay DR
OBJECTIVE: To review the efficacy and tolerability profiles of quinine in nocturnal and dialysis-associated leg cramps and to examine potential alternative agents. DATA SOURCES: Selection and extraction: a MEDLINE/PubMed, English-language literature search from 1966 to the present using quinine, leg cramps, vitamin E, verapamil, muscle relaxants, gabapentin as search terms. DATA SYNTHESIS: Quinine, an alkaloid originally isolated from the cinchona tree, has been used for many years to treat/prevent leg cramps. In the mid-1990s, the Food and Drug Administration (FDA) banned over-the-counter availability of quinine and marketing of prescription quinine products for leg cramps. In early 2007, FDA banned all prescription quinine products other than Qualaquin. FDA acted in this manner because of a perception that quinine is not effective for this condition and that its risk potential far exceeds its efficacy potential. Efficacy trials for quinine in leg cramps have numerous design flaws that have resulted in poor quality data, producing both positive and negative findings. Two meta-analyses have reached different conclusions. Superimposed on the questionable efficacy of quinine is the well-known toxicity profile of the drug, involving the hematologic, renal, neurologic, cardiac, and endocrine systems. CONCLUSION: Are there any alternatives to quinine for leg cramps? Data are available supporting the potential efficacy of verapamil, gabapentin, carisoprodol, and orphenadrine in the general population, and vitamin E in the dialysis population. One or more of these agents should be tried before resorting to a time-limited (four- to six-week) trial of quinine for the treatment/prevention of leg cramps.
Cutting edge: MHC class I-ly49 interaction regulates neuronal function.
J Immunol. 2008 May 15; 180(10): 6447-51
Zohar O, Reiter Y, Bennink JR, Lev A, Cavallaro S, Paratore S, Pick CG, Brooker G, Yewdell JW
MHC class I molecules (MHC-I) have been implicated in nervous system development in the mouse. In this study we present evidence for the interaction of MHC-I with the NK cell receptor Ly49 in primary cortical neuronal cultures. We show that MHC-I and Ly49 are expressed on neuronal soma and axon surfaces, with Ly49 also present on dendrites. Anti-MHC-I Abs reduce synapsin-I expression and enhance neurite outgrowth and neuronal death. Conversely, anti-Ly49 mAbs increase synapsin-I expression, reduce neurite outgrowth, and promote neuron viability. Because we show that Ly49 genes are selectively expressed in the adult brain, these findings suggest an unsuspected role for the MHC-I-Ly49 interaction in the development and function of the brain.