Assessment of the Effects of MPTP and Paraquat on Dopaminergic Neurons and Microglia in the Substantia Nigra Pars Compacta of C57BL/6 Mice.

The neurotoxicity of paraquat dichloride (PQ) was assessed in two inbred strains of 9- or 16-week old male C57BL/6 mice housed in two different laboratories and compared to the effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). PQ was administered by intraperitoneal injections; either once (20 mg/kg) or twice (10 mg/kg) weekly for 3 weeks, while MPTP-HCl was injected 4 times on a single day (20 mg/kg/dose). Brains were collected 8, 16, 24, 48, 96 or 168 hours after the last PQ treatment, and 48 or 168 hours after MPTP treatment.

Dietary administration of diquat for 13 weeks does not result in a loss of dopaminergic neurons in the substantia nigra of C57BL/6J mice.

Male and female C57BL/6J mice were administered diquat dibromide (DQ∙Br2) in their diets at concentrations of 0 (control), 12.5 and 62.5 ppm for 13 weeks to assess the potential effects of DQ on the nigrostriatal dopaminergic system.

Dietary administration of paraquat for 13 weeks does not result in a loss of dopaminergic neurons in the substantia nigra of C57BL/6J mice.

Several investigations have reported that mice administered paraquat dichloride (PQ·Cl2) by intraperitoneal injection exhibit a loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). In this study, male and female C57BL/6J mice were administered PQ·Cl2 in the diet at concentrations of 0 (control), 10, and 50ppm for a duration of 13weeks. A separate group of mice were administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) during week 12 as positive controls to produce a loss of dopaminergic neurons in the SNpc.

Pharmacokinetic, neurochemical, stereological and neuropathological studies on the potential effects of paraquat in the substantia nigra pars compacta and striatum of male C57BL/6J mice.

The pharmacokinetics and neurotoxicity of paraquat dichloride (PQ) were assessed following once weekly administration to C57BL/6J male mice by intraperitoneal injection for 1, 2 or 3 weeks at doses of 10, 15 or 25 mg/kg/week. Approximately 0.3% of the administered dose was taken up by the brain and was slowly eliminated, with a half-life of approximately 3 weeks.

Evidence for a separate mechanism of toxicity for the Type I and the Type II pyrethroid insecticides.

Neurotoxicity and mechanistic data were collected for six alpha-cyano pyrethroids (beta-cyfluthrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin and lambda-cyhalothrin) and up to six non-cyano containing pyrethroids (bifenthrin, S-bioallethrin [or allethrin], permethrin, pyrethrins, resmethrin [or its cis-isomer, cismethrin] and tefluthrin under standard conditions. Factor analysis and multivariate dissimilarity analysis were employed to evaluate four independent data sets comprised of (1) fifty-six behavioral and physiological parameters from an acute neurotoxicity functional observatory battery (FOB), (2) eight electrophysiological parameters from voltage clamp experiments conducted on the Na(v)1.8 sodium channel expressed in Xenopus oocytes, (3) indices of efficacy, potency and binding calculated for calcium ion influx across neuronal membranes, membrane depolarization and glutamate released from rat brain synaptosomes and (4) changes in chloride channel open state probability using a patch voltage clamp technique for membranes isolated from mouse neuroblastoma cells.

2-Halopropionic acid-induced cerebellar granule cell necrosis in the rat: in vivo and in vitro studies.

Daily oral administration of 2.3 mmol/kg L-2-chloropropionic acid (L-2-CPA), DL-2-bromopropionic acid (2-BPA) or DL-2-iodopropionic acid (2-/PA) but not DL-2-fluoropropionic acid (2-FPA) produced cerebellar granule cell necrosis in the rat. Twenty four hours after three doses of L-2-CPA or two doses of 2-BPA, animals showed clinical signs of motor incoordination and reduced hindlimb function which was associated with marked cerebellar oedema and cerebellar granule cell necrosis.

Neurotoxic effect of L-2-chloropropionic acid on primary cultures of rat cerebellar granule cells.

L-2-Chloropropionic acid (L-CPA), when administered orally to rats, produces selective necrosis to the granule cell layer of the rat cerebellum which is delayed in onset, not appearing until 36-48 h after exposure. The present study was conducted to characterise the toxic effect of L-CPA in primary cell cultures of rat cerebellar granule cells in vitro. Exposure to L-CPA produced a time and concentration dependent loss in cerebellar granule cell viability.

Methyl iodide toxicity in rat cerebellar granule cells in vitro: the role of glutathione.

The monohalomethane methyl iodide (MeI) is toxic to a number of organ systems including the central nervous system. Clinical symptoms of neurotoxicity suggest that the cerebellum is the target within the brain, and we have now modelled the toxicity of MeI in cultured rat cerebellar granule cells. Cytotoxicity is maximal 24 h after a 5 min exposure to MeI, and the EC50 for MeI under these conditions was calculated to be 1.

Characterisation of kainate receptor mediated whole-cell currents in rat cultured cerebellar granule cells.

Whole-cell voltage clamp recordings have been used to identify and characterise inward currents mediated by native kainate receptors in rat cultured cerebellar granule cells. While the selective AMPA receptor antagonist GYKI 53655 (50 microM) completely abolished inward currents evoked by AMPA (10-100 microM) in the presence of cyclothiazide (100 microM), kainate evoked currents in cells pretreated with concanavalin A (Con A) always showed a component (35-140 pA, n = 13) resistant to blockade. The majority (73+/-7%, n = 5) of GYKI 53655-resistant kainate-evoked inward currents remained in the presence of 100 microM AMPA.

L-2-chloropropionic acid inhibits glutamate and aspartate release from rat cerebellar slices but does not activate cerebellar NMDA receptors: implications for L-2-chloropropionic acid-induced neurotoxicity.

L-2-Chloropropionic acid (L-CPA), when orally administered at single high dose to rats produces a selective lesion in the cerebellum involving destruction of a high proportion of granule cells by a mechanism which involves N-methyl-D-aspartate (NMDA) receptors. Receptor binding studies demonstrated that L-CPA a had low affinity at the glutamate and glycine binding sites at NMDA receptors (530-660 microM), respectively, whereas L-CPA did not displace [3H]AMPA, [3H]NBQX or [3H]kainate from AMPA or kainate receptors. Whole cell-patch clamp experiments using cultured granule cells failed to demonstrate changes in membrane potential of cultured granule cells when either L-CPA (0.

Monocyte chemoattractant protein-1: receptor interactions and calcium signaling mechanisms.

Monocyte chemoattractant protein-1 (MCP-1) is a member of the Cys-Cys chemokine family. Two related MCP-1 receptors have been identified (CC-CKR2A and CC-CKR2B), although the precise kinetics of ligand binding and calcium signaling of these receptors has yet to be investigated. To examine this more closely, the human MCP-1 receptors were cloned and expressed in Chinese hamster ovary (CHO) cells.

High level expression of human MCP-1 using the LCR/MEL expression system.

We have expressed human monocyte chemoattractant protein-1 (hMCP-1) in preerythroid mouse erythroleukemia (MEL) C88 cells using the locus control region/MEL expression system and studied the biological activity of the purified protein in a range of in vitro experimental systems. The recombinant hMCP-1 is expressed at high levels (approximately 10 mg/liter) in this system and is modified in a manner which is very similar to native hMCP-1. We have developed a simple high-yielding two-step purification route employing dye ligand and ion exchange chromatographies which enables us to separate glycosylated and unglycosylated hMCP-1.

Inhibitory actions of ZENECA ZD7288 on whole-cell hyperpolarization activated inward current (If) in guinea-pig dissociated sinoatrial node cells.

1. ZENECA ZD7288 (4-(N-ethyl-N-phenylamino)-1,2-dimethyl-6-(methylamino) pyridinium chloride) is a sinoatrial node (SAN) modulating agent which produces a selective slowing of the heart rate. Its effects have been studied in single, freshly dissociated guinea-pig SAN cells, by standard patch clamp procedures.

Voltage-activated currents in the CRI-G1 rat insulin-secreting cell-line.

1. The whole-cell configuration of the patch-clamp recording technique was used to characterize the electrophysiological properties of CRI-G1 insulin-secreting cells. 2.

Steroid modulation of the GABAA receptor complex: electrophysiological studies.

The effect of some endogenous and synthetic steroids on the operation of inhibitory and excitatory amino acid neurotransmitter receptors was examined. Anaesthetic pregnane steroids (e.g.

Effects of sulphonylureas and diazoxide on insulin secretion and nucleotide-sensitive channels in an insulin-secreting cell line.

1. The effects of various sulphonylureas and diazoxide on insulin secretion and the activity of various channels have been studied using tissue culture and patch-clamp methods in an insulin-secreting cell line derived from a rat islet cell tumour. 2.

Adenosine-5'-triphosphate-sensitive ion channels in neonatal rat cultured central neurones.

ATP-sensitive channels were observed in isolated inside-out membrane patches from rat cultured central neurones. Two types of ATP-sensitive K+ channels were present in cortical neurones, one which had its open-state probability increased, the other its open-state probability decreased by application of ATP to the cytoplasmic membrane surface. Another, ATP-sensitive channel differing in ion conductance from all previously reported ATP-sensitive channels was also seen in patches from cortical neurones.

Nucleotide-sensitive ion channels in human insulin producing tumour cells.

Cells from a human insulin producing tumour have been studied and single channel currents recorded. We have observed three main cation-selective channels in excised patch experiments. An ATP-sensitive potassium channel is present the activity of which can be inhibited by the oral hypoglycaemic drug, tolbutamide.

Calcium and ATP regulate the activity of a non-selective cation channel in a rat insulinoma cell line.

A calcium-activated non-selective cation channel was observed in isolated plasma membrane patches from an insulin-secreting cell line (CRI-Gl). The conductance of the channel was approximately 25 pS with identical (140 mM KCl) solutions on either side of the membrane. However, some rectification was observed (smaller outward current) when sodium ions were present extracellularly.

Inhibition of a calcium-activated, non-selective cation channel, in a rat insulinoma cell line, by adenine derivatives.

The effects of adenosine and adenine nucleotides on a calcium-activated non-selective cation channel, present in the plasma membrane of an insulin-secreting cell line CRI-Gl were investigated. Single-channel currents were recorded from inside-out membrane patches and the adenine derivatives applied to the solution bathing the cytoplasmic aspect of the membrane surface. The activity of this channel is shown to be inhibited by all the derivatives tested.

Single channel recordings of potassium currents in an insulin-secreting cell line.

Using the patch-clamp technique we observed three distinct classes of K+ channels which were spontaneously active in excised 'inside-out' membrane patches from an insulin-secreting rat pancreatic islet cell line (CRI-G1). Two of these occurred infrequently, one with a conductance of approximately 7 pS, and the other a conductance of 220 pS. The activation of the 220 pS K+ channel was dependent upon the membrane voltage and was sensitive to the concentration of calcium ions at the cytoplasmic surface of the membrane.