Journal of neurophysiology
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Nitric oxide (NO) in the paraventricular nucleus (PVN) is involved in the regulation of the excitability of PVN neurons. However, the effect of NO on the inhibitory GABAergic and excitatory glutamatergic inputs to spinally projecting PVN neurons has not been studied specifically. In the present study, we determined the role of the inhibitory GABAergic and excitatory glutamatergic inputs in the inhibitory action of NO on spinally projecting PVN neurons. ⋯ On the other hand, 20 microM bicuculline significantly increased the impulse activity of PVN neurons. In the presence of bicuculline, SNAP or L-arginine both failed to inhibit the firing activity of PVN neurons. This electrophysiological study provides substantial new evidence that NO suppresses the activity of spinally projecting PVN neurons through potentiation of the GABAergic synaptic input.
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Comparative Study
Neural activity in monkey dorsal and ventral cingulate motor areas: comparison with the supplementary motor area.
The cingulate motor areas are a recently discovered group of discrete cortical regions located in the cingulate sulcus with direct connections to the primary motor cortex and spinal cord. Although much is known about their anatomical relationship with other motor areas, relatively little is known about their functional neurophysiology. We investigated neural mechanisms of motor processing in the dorsal and ventral cingulate motor areas (CMAd and CMAv) during two-dimensional visually guided arm movements. ⋯ These results indicate that CMAd and CMAv participate in the visual guidance of limb movements using similar neurophysiological mechanisms as SMA. The earlier average onset and shorter duration of movement activity in SMA suggest a more prominent role for this area in movement initiation, whereas the later onset and longer duration of movement activity in CMAd and CMAv suggest a more influential role in movement execution. Notwithstanding these differences, however, the remarkable similarities in response types and their combinatorial organization within single neurons across all cortical areas attests to the parallel organization and distributed nature of information processing in these three motor areas.
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Section of rat sciatic nerve (axotomy) increases the excitability of neurons in the L(4)-L(5) dorsal root ganglia (DRG). These changes are more pronounced in animals that exhibit a self-mutilatory behavior known as autotomy. We used whole cell recording to examine changes in the tetrodotoxin-sensitive (TTX-S) and the tetrodotoxin-resistant (TTX-R) components of sodium channel currents (I(Na)) that may contribute to axotomy-induced increases in excitability. ⋯ In addition, the presence of autotomy correlates with an increase in excitability of "large" rather than "small" cells. Increases in TTX-R and TTX-S I(Na) thus coincide with axotomy-induced increases in excitability and alterations in spike shape across the whole population of sensory neurons. Injury-induced changes of this type are likely associated with the onset of chronic pain in humans.