Penehyclidine hydrochloride protects against oxygen and glucose deprivation injury by modulating amino acid neurotransmitters release

Abstract

Penehyclidine hydrochloride (PHC) is an anticholinergic agent, with only high degree of selectivity for M₁ and M₃ receptor subtypes. In this study, we investigated whether PHC could play a protective effect on hippocampal slice against oxygen and glucose deprivation (OGD), as well as related to the change of amino acid neurotransmitters release. Penehyclidine hydrochloride 2, 10, and 50 μM doses were adopted in the lactate dehydrogenase (LDH) leakage assay and triphenyl tetrazolium chloride (TTC) staining. The spontaneous miniature excitatory postsynaptic currents (mEPSCs) and amino acid neurotransmitters were detected by electrophysiology method and high-performance liquid chromatography (HPLC), respectively. Our study showed that PHC can lessen the LDH leakage ratio and tissue injury values according to TTC staining. Penehyclidine hydrochloride decreased the content of aspartate acid (Asp) and glutamate (Glu), and elevated the content of glycine (Gly) and gamma-aminobutyric acid (GABA). Ischemia increased the amplitude and frequency of the mEPSCs, but PHC obviously decreased the frequency and amplitude of mEPSCs. Thus, the study reveals the fact that PHC protects hippocampus slice against OGD injury by decreasing excitatory amino acids release and increasing inhibitory amino acids release.     

Calcium influx via L-type voltage-gated channels mediates the delayed,elevated increases in steady-state c-fos mRNA levels in cerebellar granule cells exposed to excitotoxic levels of glutamate

The altered kinetics of steady-state c-fos mRNA production in cultured cerebellar granule cells under excitotoxic conditions was investigated in neurons subjected to depolarising stimuli, namely, high KCl and L-glutamate (Glu), in which Ca²⁺ influx occurs by differing routes. Increases in intracellular-free calcium levels ([Ca²⁺]_i) stimulated by nontoxic or toxic levels of Glu were blocked by selective N-methyl-D-aspartate (NMDA) receptor antagonism; were blocked only partially by the L-type channel blocker, nifedipine; and were unaffected by α-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)/kainate receptor antagonists. Glu-induced cell death was prevented only by NMDA receptor blockade. Exposure of cells to nontoxic levels of Glu resulted in a transient increase in c-fos mRNA levels, whereas an excitotoxic dose produced a delay in the appearance of c-fos mRNA but a subsequent, progressive, and sustained (>4 hr) increase. An excitotoxic dose of Glu in combination with either nifedipine or selective NMDA receptor antagonists resulted in the normal, transient increase of c-fos mRNA levels. Chronic exposure to 55 mM KCl caused no cytotoxicity, although it resulted in a delayed, elevated increase in c-fos mRNA levels that was unaffected by NMDA receptor blockade but reverted to the normal, transient profile of c-fos mRNA formation when it was coadministered with nifedipine. The KCl-induced increase in [Ca²⁺]_i levels was inhibited dramatically by nifedipine but was unaffected by any of the ionotropic Glu receptor antagonists. The results support the notion that the appearance of a delayed but elevated increase in steady-state c-fos mRNA levels following exposure to excitotoxic doses of Glu is mediated specifically by calcium influx via L-type voltage-gated channels. J. Neurosci. Res. 52:641–652, 1998. © 1998 Wiley-Liss, Inc.     

Polychlorinated biphenyl mixture aroclor 1254-induced oxidative stress plays a role in dopaminergic cell injury

Oxidative stress (OS) is thought to participate in the pathogenesis of neurodegenerative disorders, including Parkinson's disease (PD). Excessive reactive oxygen species (ROS) production can occur during the normal aging process or following exposure to environmental toxicants. Dopamine neurons, which degenerate during PD, are particularly sensitive to oxidative stress. Polychlorinated biphenyls (PCBs), persistent and widespread pollutants, have been shown to adversely impact dopaminergic (DAergic) pathways, but the role ROS play in neurotoxicity remains unclear. To test the hypothesis that PCB exposure compromises dopamine neurons by stimulating ROS production, the direct toxicity and oxidative stress response following PCB exposure was examined both in MN9D dopamine cells and primary mesencephalic cultures. PCBs induced a time- and concentration-dependent increase in ROS production, which preceded cytotoxicity. Whereas intracellular GSH depletion exacerbated PCB effects, antioxidant pretreatment attenuated ROS production and cell death. Coincident alterations in antioxidant defense enzymes also accompanied ROS production, including decreased MnSOD and increased CuZnSOD protein levels. The robust elevation in heme oxygenase-1 levels further support the activation of oxidative stress mechanisms following PCB exposure. Furthermore, PCBs produced concentration-dependent reductions in intracellular dopamine levels and elevated dopamine turnover. Although the intracellular source of ROS remains unknown, these results suggest that sublethal PCB concentrations activate an oxidative stress-related pathway, which potentially disrupts dopamine neuron function.     

Cerebellar granule cell and Bergmann glial cell maturation in the rat is disrupted by pre- and post-natal exposure to moderate levels of ethanol

Migration of the external granular layer cells in the cerebellum of rats was delayed after exposure to moderate levels of ethanol during a pre-gestational period, through gestation and lactation until weaning. After ethanol withdrawal, cell soma and dendrites were observed to be larger in granule cells. Likewise, Bergmann glia showed several cytoarchitectonic features suggesting cell immaturity, as well as some apparent compensatory plastic responses after ethanol withdrawal. These effects may be due to ethanol impairing neurotrophin-mediated processes during cerebellar development that could lead to alterations in Purkinje cell structure and activity, and thereafter in the psychoneural functions in which the cerebellar cortex is involved.