No abstract

Calbindin D-28k (CB), calretinin (CR), substance P (SP), limbic system-associated membrane protein (LAMP), choline acetyltransferase (ChAT), and acetylcholinesterase (AChE) were used as chemical markers to investigate the organization of the ventral striatum (VST) and adjacent structures in healthy human individuals. No clear boundary could be established between the dorsal striatum and the VST, and the core/shell subdivisions of nucleus accumbens (Acb) could be distinguished only at the midrostrocaudal level of the VST. The CB-poor shell displayed intense immunostaining for SP and CR but only weak staining for LAMP. By contrast, the core was weakly stained for SP and CR and moderately stained for LAMP and CB. There was no difference between shell and core with regard to the cholinergic markers. The Acb harbored numerous ChAT- and CR-immunoreactive cell bodies, the latter being distributed according to a marked, mediolaterally increasing gradient. The size of the ChAT- and CR-immunoreactive perikarya in the Acb varied according to their location in the core and shell. The VST was surrounded by a chemically heterogeneous group of cell clusters referred to as interface islands. The CR-rich caudal portion of the VST merged with the bed nucleus of the stria terminalis dorsally and the diagonal band of Broca ventromedially, the latter two structures displaying complex immunostaining patterns. The claustrum was markedly enriched in LAMP and harbored different types of CR- and CB-immunopositive neurons. These results demonstrate that the neurochemical organization of the human VST is strikingly complex and exhibits a greater heterogeneity than the dorsal striatum.

No abstract

Norepinephrine (NE) is released in excess into the extracellular space during oxygen-glucose deprivation (OGD) in brain, increasing neuronal metabolism and aggravating glutamate excitoxicity. We used isolated rat optic nerve and spinal cord dorsal columns to determine whether the noradrenergic system influences axonal damage in white matter. Tissue was studied electrophysiologically by recording the compound action potential (CAP) before and after exposure to 60 min of OGD at 36°C. Depleting catecholamine stores with reserpine was protective and improved CAP recovery after 1 h of reperfusion from 17% (control) to 35%. Adding NE during OGD decreased CAP recovery to 8%, and adding NE to reserpine during OGD eliminated the protective effect of the latter. Selective inhibitors of Na ϩ -dependent norepinephrine transport desipramine and nisoxetine improved recovery to 58% and 44%, respectively. ␣2 adrenergic receptor agonists UK14,304 and medetomidine improved CAP recovery to 41% and 46% after 1 h of OGD. Curiously, ␣2 antagonists alone were also highly protective (e.g., atipamezole: 86% CAP recovery), at concentrations that did not affect baseline excitability. The protective effect of ␣2 receptor modulation was corroborated by imaging fluorescent Ca 2ϩ and Na ϩ indicators within axons during OGD. Both agonists and antagonists significantly reduced axonal Ca 2ϩ and Na ϩ accumulation in injured axons. These data suggest that the noradrenergic system plays an active role in the pathophysiology of axonal ischemia and that ␣2 receptor modulation may be useful against white matter injury.

Multi-scale interactions between El Nino-Southern Oscillation (ENSO) and the Boreal Winter Monsoon contribute to rainfall variations over Malaysia. Understanding the physical mechanisms that control these spatial variations in local rainfall is crucial for improving weather and climate prediction and related risk management. Analysis using station observations and ERA-interim reanalysis reveals a significant decrease in rainfall during El Nino (EL) and corresponding increase during La Nina (LA) particularly north of 2ºN over Peninsular Malaysia (PM). It is noted that the southern tip of PM shows a small increase in rainfall during El Nino although not significant. Analysis of the diurnal cycle of rainfall and winds indicates that there are no significant changes in morning and evening rainfall over PM that could explain the north-south disparity. Thus, we suggest that the key factor which might explain the north-south rainfall disparity is the moisture flux convergence (MFC). During the December to January (DJF) period of EL years, except for the southern tip of PM, significant negative MFC causes drying as well as suppression of uplift over most areas. In addition, lower specific humidity combined with moisture flux divergence results in less moisture over PM. Thus, over the areas north of 2ºN, less rainfall (less heavy rain days) with smaller diurnal rainfall amplitude explains the negative rainfall anomaly observed during DJF of EL. The same MFC argument might explain the dipolar pattern over other areas such as Borneo if further analysis is performed.