Neuroprotective sigma ligands interfere with the glutamate‐activated NOS pathway in hippocampal cell culture

Abstract

We studied neuroprotective properties of 12 structurally different sigma site ligands in primary rat hippocampal cell cultures and analyzed whether they interfere with glutamate-induced activation of the nitric oxide synthase (NOS) pathway. Neurotoxicity was triggered with 1 mM glutamate on day 8 of culture. Cells were treated with various concentrations of the compounds for 7 days before glutamate exposure (prolonged pretreatment), or during glutamate exposure (acute treatment). Protection was seen after prolonged pretreatment (long-term protection) with sabeluzole, opipramole, haloperidol, ifenprodil, fenpropimorph, carbetapentane, and tiospirone, with pIC50s of 7.30, 7.15, 6.87, 6.68, 6.66, 6.39, and 6.34, respectively. There was no protection with PD 128298, 1,3-ortho-di-tolylguanidine, BMY-14802, (+)3-(3-hydroxyphenyl)-N-1(propyl) piperidine, or dextromethorphan. Upon acute treatment, only ifenprodil was protective. Interference of the drugs with glutamate activation of the NOS pathway was determined by measuring glutamate-activated cGMP formation and citrulline levels. Glutamate-activated cGMP formation was reduced by all neuroprotective sigma ligands after prolonged pretreatment but not after acute treatment. Sigma ligands added to cell culture lysate did not reduce citrulline formation, evidence that there was no direct effect on the NOS enzyme. We conclude that some but not all sigma ligands exert long-term protective properties against glutamate-induced neurotoxicity in primary hippocampal cultures, and that this protection is accompanied by attenuation of cGMP formation in the NOS pathway. However, inhibition of cGMP formation by itself appeared not sufficient for obtaining neuroprotective effects, as inhibition of glutamate-activated cGMP formation by N omega-nitro-L-arginine, haemoglobin, or PD128298 did not provide neuroprotection.

Dextromethorphan Protects Dopaminergic Neurons against Inflammation-Mediated Degeneration through Inhibition of Microglial Activation

“…Over the years, a number of studies have reported that DM has neuroprotective effects (Choi 1987;Steinberg et al, 1988;George et al, 1988;Prince and Feeser, 1988;Monyer and Choi, 1988;DeCoster et al, 1995;Lesage et al, 1995;Berman and Murray, 1996;Britton et al, 1997;Haberecht et al, 1997). The mechanism of action responsible for this neuroprotective activity has been attributed to DM's potential antagonistic effect on the NMDA receptor complex.…”

“…Nevertheless, studies using animal models of cerebral ischemia and hypoglycemic neural injuries have demonstrated that DM possesses neuroprotective activity Monyer and Choi, 1988;Prince and Feeser, 1988;Steinberg et al, 1988;Britton et al, 1997;Tortella et al, 1999). Attempts to attribute the neuroprotective activity of DM to antagonism of glutamate receptors have been complicated by conflicting reports about its ability to prevent glutamate excitatory toxicity (Choi, 1987;DeCoster et al, 1995;Lesage et al, 1995;Berman and Murray, 1996;Haberecht et al, 1997). Nevertheless, the effect of DM on the degeneration of dopaminergic neurons has not been studied.…”

Differentiation of σ ligand‐activated receptor subtypes that modulate NMDA‐evoked [3H]‐noradrenaline release in rat hippocampal slices

“…Disfinct sensitivity of a sites to antagonists Behavioural, neurochemical and electrophysiological studies led to the discovery of the neuromodulatory effects of a receptor ligands on NMDA(N-methyl-D-aspartate)-operated glutamatergic neurotransmission, effects which would account for the neuroprotective actions, amnesic and cognitive effects of a drugs (Monnet et al, 1990;1992a;Pontecorvo et al, 1991;Martin et al, 1992;Maurice et al, 1994a, b;DeCoster et al, 1995;Lesage et al, 1995;Lockhart et al, 1995). In an in vivo extracellular electrophysiological paradigm, a ligands that enhance the neuronal response to NMDA were defined as a agonists [e.g.…”

Neuroprotective Effect of σ 1 -Receptor Ligand 4-Phenyl-1-(4-Phenylbutyl) Piperidine (PPBP) Is Linked to Reduced Neuronal Nitric Oxide Production

“…15 In vitro, -receptor ligands prevent glutamate-induced activation of nitric oxide synthase (NOS). 16 Nitric oxide (NO) is an important mediator in ischemic brain injury. [17][18][19] Specifically, NO derived from constitutively expressed NOS in neurons (nNOS) and the inducible isoform expressed by many cells (iNOS) are important in excitotoxic injury cascades.…”