Background: Spinal synaptic plasticity may contribute to paclitaxel-induced painful neuropathy. Results: Paclitaxel treatment impairs GABA-mediated neuronal inhibition and increases total and plasma membrane NKCC1 protein levels in the spinal cord. Blocking NKCC1 reverses paclitaxel effects on synaptic inhibition and pain hypersensitivity. Conclusion: Paclitaxel diminishes synaptic inhibition in the spinal cord. Significance: This study demonstrates how disrupting microtubule dynamics causes synaptic plasticity and neuropathic pain.

SUMMARY Lipid rafts are specialized membrane microdomains that function as signaling platforms across plasma membranes of many animal and plant cells. Although there are several studies implicating the role of lipid rafts in capacitation of mammalian sperm, the function of these structures in sperm motility activation and chemotaxis remains unknown. In the ascidian Ciona intestinalis, egg-derived sperm activating- and attracting-factor (SAAF) induces both activation of sperm motility and sperm chemotaxis to the egg. Here we found that a lipid raft disrupter, methyl-b-cyclodextrin (MCD), inhibited both SAAF-induced sperm motility activation and chemotaxis. MCD inhibited both SAAF-promoted synthesis of intracellular cyclic AMP and sperm motility induced by ionophore-mediated Ca2þ entry, but not that induced by valinomycin-mediated hyperpolarization. Ca2þ-imaging revealed that lipid raft disruption inhibited Ca2þ influx upon activation of sperm motility. The Ca2þ-activated adenylyl cyclase was clearly inhibited by MCD in isolated lipid rafts. The results suggest that sperm lipid rafts function in signaling upstream of cAMP synthesis, most likely in SAAF-induced Ca2þ influx, and are required for Ca2þ-dependent pathways underlying activation and chemotaxis in Ciona sperm.

The hypothalamic paraventricular nucleus (PVN) is critically involved in elevated sympathetic output and the development of hypertension. However, changes in group I metabotropic glutamate receptors (mGluR1 and mGluR5) and their relevance to the hyperactivity of PVN presympathetic neurons in hypertension remain unclear. Here, wefoundthat selectively blocking mGluR5 significantly reducedthe basal firing activity of spinally projecting PVN neurons in spontaneously hypertensive rats (SHRs), but not in normotensive WistarKyoto (WKY) rats. However, blocking mGluR1 had no effect onthe firing activity of PVN neurons in either group. The mRNA and protein levels of mGluR5 in the PVN and rostral ventrolateral medulla were significantly higher in SHRs than in WKY rats. The group I mGluR selective agonist (S)-3,5-dihydroxyphenylglycine (DHPG) similarly increased the firing activity of PVN neurons in WKY rats and SHRs. In addition, blocking NMDA receptors (NMDARs)through bath application or intracellular dialysis not only decreasedthe basal firing in SHRs, but also eliminated DHPG-induced excitation of spinally projecting PVN neurons. DHPG significantly increased the amplitude of NMDAR currents without changing their decay kinetics. Interestingly, DHPG still increased the amplitude of NMDAR currents and caused reappearance of functional NMDAR channels after initially blocking NMDARs. In addition, protein kinase C (PKC) inhibition or intracellular dialysis with synaptosomal-associated protein of 25 kDa (SNAP-25)-blocking peptide abolished DHPG-induced increases in NMDAR currents of PVN neurons in SHRs. Our findings suggest that mGluR5 in the PVN is upregulated in hypertension and contributes to the hyperactivity of PVN presympathetic neurons through PKC- and SNAP-25-mediated surface expression of NMDARs.

Abstract The main physiological role of somatostatin (SST) is the control of hormone secretion. Recently, SST has been shown to exert antiproliferative effects on some human tumors via both direct and indirect mechanisms. We have previously found that in the human neuroblastoma cell line SY5Y the SST analogue lanreotide (BIM 23014) inhibited serum-stimulated cell proliferation and MAP kinase activity. Here, we examine the effect of SST on PDGF-induced Ras activation. We found that SST suppressed PDGF-induced Ras activation in a pertussis toxin (PTx)-independent and peroxovanadate-dependent manner. Ras-specific GTPase activating protein (GAP) activities were not altered by SST treatment. On the contrary, PDGF-induced PDGF receptor phosphorylation was decreased by SST in a PTx-independent, peroxovanadate-dependent manner, likely accounting for the SST-mediated inhibition of PDGF-induced Ras activation.

Abstract In the mature auditory system, inner hair cells (IHCs) convert sound-induced vibrations into electrical signals that are relayed to the central nervous system via auditory afferents. Before the cochlea can respond to normal sound levels, developing IHCs fire calcium-based action potentials that disappear close to the onset of hearing. Action potential firing triggers transmitter release from the immature IHC that in turn generates experience-independent firing in auditory neurons. These early signaling events are thought to be essential for the organization and development of the auditory system and hair cells. A critical component of the action potential is the rise in intracellular calcium that activates both small conductance potassium channels essential during membrane repolarization, and triggers transmitter release from the cell. Whether this calcium signal is generated by calcium influx or requires calcium-induced calcium release (CICR) is not yet known. IHCs can generate CICR, but to date its physiological role has remained unclear. Here, we used high and low concentrations of ryanodine to block or enhance CICR to determine whether calcium release from intracellular stores affected action potential waveform, interspike interval, or changes in membrane capacitance during development of mouse IHCs. Blocking CICR resulted in mixed action potential waveforms with both brief and prolonged oscillations in membrane potential and intracellular calcium. This mixed behavior is captured well by our mathematical model of IHC electrical activity. We perform two-parameter bifurcation analysis of the model that predicts the dependence of IHCs firing patterns on the level of activation of two parameters, the SK2 channels activation and CICR rate. Our data show that CICR forms an important component of the calcium signal that shapes action potentials and regulates firing patterns, but is not involved directly in triggering exocytosis. These data provide important insights into the calcium signaling mechanisms involved in early developmental processes.