Neuroscience
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Neuropeptide expression in primary sensory neurons is highly plastic in response to peripheral nerve axotomy. While neuropeptide changes following complete sciatic nerve injury have been extensively studied, much less is known about the effects of partial sciatic nerve injuries on neuropeptide plasticity. Galanin. a possible endogenous analgesic peptide, was up-regulated in primary sensory neurons following complete sciatic nerve injury. ⋯ Furthermore, more galanin-immunoreactive axonal fibres were observed in the ipsilateral gracile nuclei of partially injured rats than in completely injured rats. We conclude that partial sciatic nerve injuries induced greater galanin up-regulation in medium- and large-size dorsal root ganglion neurons than complete sciatic nerve injury. Galanin expression in primary sensory neurons seems to be differentially regulated following partial and complete sciatic nerve injuries.
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Electrophysiological techniques and computational methods were used to study the effect of the selective serotonin reuptake inhibitors fluvoxamine, paroxetine and sertraline on the basal activity of dopamine neurons in the ventral tegmental area. Acute injection of fluvoxamine, paroxetine and sertraline (20-1280 microg/ kg, i.v.) caused a dose-dependent inhibition of some ventral tegmental area DA neurons but it did not affect the basal firing rate of other DA cells. A Fast-Fourier-Transformation based analysis of the basal activity of 32 ventral tegmental area DA neurons showed a positive correlation between the value of a functional operator (psi) equivalent to the density-power-spectrum of the signals and the degree of selective serotonin reuptake inhibitor-induced inhibition of ventral tegmental area DA cells. ⋯ The neurons belonging to subclass A showed a more regular behavior of the interspike interval functions corresponding to lower values detected by the functional operator psi, whereas the neurons belonging to subclass B showed a less regular behavior of interspike interval functions corresponding to higher psi values detected by the same functional operator. Fluvoxamine, paroxetine and sertraline also caused a dose-dependent increase of the percentage of spikes occurring in bursts in neurons belonging to subclass A (low values of psi), whereas the mean basal firing rate of these cells was not affected. It is suggested that this difference in density-power-spectrum could reflect the asymmetry of serotonergic input to the ventral tegmental area DA neurons, and the differential effects of selective serotonin reuptake inhibitors on these neurons might depend on the characteristics of their basal firing mode.