Development of a regional hydrologic soil model and application to the Beerze--Reusel drainage basin.

The soil compartment is an important interface between the atmosphere and the subsurface hydrosphere. In this paper a conceptual approach for regional hydrologic soil modelling (RHSM) is presented, which provides two important qualities for modelling. First, the soil compartment is directly coupled to the atmosphere via the land surface and to the aquifers. Second, extremely fine (5cm vertical) resolutions of the soil system can be realized at regional scales (several hundreds of km(2)). This high-resolution modelling could be achieved by parallel computation techniques. The RHSM approach is applied to the Beerze-Reusel drainage basin, which belongs to the Meuse River basin. Moisture transport in the soil system was calculated with extremely high vertical resolution at a regional scale based on rainfall-evaporation data for the year 2000. As a result, highly resolved regional groundwater recharge pattern addressing the heterogeneity of soil systems could be determined.

Selective vulnerability of spinal cord motor neurons to non-NMDA toxicity.

We previously reported that alpha-motor neurons in organotypic cultures of rat spinal cord (OTC-SC) are resistant to excitotoxicity induced through NMDA receptors. Here we describe the effects of non-NMDA glutamate receptor agonists kainic acid (KA) and quisqualic acid (QUIS) on motor neurons in OTC-SC. Large ventral horn acetylcholinesterase-positive neurons (VHANs), most of which are motor neurons, were quite sensitive to QUIS and KA toxicity and displayed losses of 95% and 94%, respectively. Small VHANs were reduced by 41% and 61% only. Identical results were obtained in cultures stained for non-phosphorylated neurofilaments. These observations demonstrate that alpha-motor neurons are considerably more sensitive to KA and QUIS than to NMDA toxicity. The proposed excitotoxic mechanism of ALS, therefore, is most likely mediated through non-NMDA glutamate receptors.

Noradrenaline in the ventral forebrain is critical for opiate withdrawal-induced aversion.

Cessation of drug use in chronic opiate abusers produces a severe withdrawal syndrome that is highly aversive, and avoidance of withdrawal or associated stimuli is a major factor contributing to opiate abuse. Increased noradrenaline in the brain has long been implicated in opiate withdrawal, but it has not been clear which noradrenergic systems are involved. Here we show that microinjection of beta-noradrenergic-receptor antagonists, or of an alpha2-receptor agonist, into the bed nucleus of the stria terminalis (BNST) in rats markedly attenuates opiate-withdrawal-induced conditioned place aversion. Immunohistochemical studies revealed that numerous BNST-projecting cells in the A1 and A2 noradrenergic cell groups of the caudal medulla were activated during withdrawal. Lesion of these ascending medullary projections also greatly reduced opiate-withdrawal-induced place aversion, whereas lesion of locus coeruleus noradrenergic projections had no effect on opiate-withdrawal behaviour. We conclude that noradrenergic inputs to the BNST from the caudal medulla are critically involved in the aversiveness of opiate withdrawal.

Clonidine blocks stress-induced reinstatement of heroin seeking in rats: an effect independent of locus coeruleus noradrenergic neurons.

Using a reinstatement procedure, it has been shown that intermittent footshock stress reliably reinstates extinguished drug-taking behaviour in rats. Here we studied the role of noradrenaline (NE), one of the main brain neurotransmitters involved in responses to stress, in reinstatement of heroin seeking. We first determined the effect of clonidine, an alpha-2 adrenergic receptor agonist that decreases NE cell firing and release, on stress-induced reinstatement of heroin seeking. Rats were trained to self-administer heroin (0.1 mg/kg per infusion, IV, three 3-h sessions per day) for 9-10 days. Extinction sessions were given for up to 11 days during which saline was substituted for the drug. Tests for reinstatement were then conducted after exposure to intermittent footshock (5, 15 and 30 min, 0.5 mA). During testing, clonidine was injected systemically (10-40 microgram/kg, i.p.) or directly into the lateral or fourth ventricles (1-3 microram). Clonidine (1-2 microgram per site) or its charged analogue, 2-[2, 6-diethylphenylamino]-2-imidazole (ST-91, 0.5-1 microgram per site), was also injected bilaterally into the locus coeruleus (LC), the main noradrenergic cell group in the brain. Clonidine blocked stress-induced reinstatement of drug seeking when injected systemically or into the cerebral ventricles. In contrast, neither clonidine nor ST-91 consistently altered stress-induced reinstatement when injected into the locus coeruleus. We therefore studied the effect of lesions of the lateral tegmental NE neurons on stress-induced reinstatement. 6-Hydroxydopamine (6-OHDA) lesions performed after training for heroin self-administration had no effect on extinction of heroin-taking behaviour, but significantly attenuated reinstatement induced by intermittent footshock. These data suggest that: (i) clonidine prevents stress-induced relapse to heroin seeking by its action on neurons other than those of the locus coeruleus; and (ii) activation of the lateral tegmental NE neurons contributes to stress-induced reinstatement of heroin seeking.

The bed nucleus of the stria terminalis. A target site for noradrenergic actions in opiate withdrawal.

Hyperactivity of brain norepinephrine (NE) systems has long been implicated in mechanisms of opiate withdrawal (OW). However, little is known about where elevated NE may act to promote OW. Here we report that the bed nucleus of the stria terminalis (BNST), the densest NE target in the brain, is critical for NE actions in OW. (1) Many BNST neurons become Fos+ after OW. Pretreatment with the beta antagonist, propranolol, markedly reduces OW symptoms and the number of Fos+ cells in the BNST. (2) Numerous neurons in the nucleus tractus solitarius (A2 neurons) and the A1 cell group are triple labeled for tyrosine hydroxylase, a retrograde tracer from the BNST, and Fos after OW, revealing numerous NE neurons that project to the BNST from the medulla that are stimulated by OW. Fewer such triple-labeled neurons were found in the locus caeruleus. (3) Behavioral studies reveal that local microinjections of selective beta-adrenergic antagonists into the BNST attenuate OW symptoms. In particular, withdrawal-induced place aversion is abolished by bilateral microinjection of a cocktail of selective beta 1 (betaxolol) plus the beta 2 (ICI 181,555) antagonists (1.0 nmol each/0.5 microL per side) into the BNST. Similar results were obtained with neurochemically selective lesions of the ventral ascending NE bundle, the pathway for A1 and A2 projections to the BNST. Similar lesions of the dorsal NE bundle of projections from the locus caeruleus had no effect on either aversive or somatic withdrawal symptoms. Together, these results indicate that beta-receptor activation in the BNST is critical for aversive withdrawal symptoms, and that A1 and A2 neurons in the medulla are the source of this critical NE.

Presynaptic inhibition of GABA(B)-mediated synaptic potentials in the ventral tegmental area during morphine withdrawal.

Opioids increase the firing of dopamine cells in the ventral tegmental area by presynaptic inhibition of GABA release. This report describes an acute presynaptic inhibition of GABAB-mediated IPSPs by mu- and kappa-opioid receptors and the effects of withdrawal from chronic morphine treatment on the release of GABA at this synapse. In slices taken from morphine-treated guinea pigs after washing out the morphine (withdrawn slices), a low concentration of a mu receptor agonist increased, rather than decreased, the amplitude of the GABAB IPSP. In withdrawn slices, after blocking A1-adenosine receptors with 8-cyclopentyl-1, 3-dipropylxantine, mu-opioid receptor activation inhibited the IPSP at all concentrations and increased the maximal inhibition. In addition, during withdrawal, there was a tonic increase in adenosine tone that was further increased by forskolin or D1-dopamine receptor activation, suggesting that metabolism of cAMP was the source of adenosine. The results indicate that during acute morphine withdrawal, there was an upregulation of the basal level of an opioid-sensitive adenylyl cyclase. Inhibition of this basal activity by opioids had two effects. First, a decrease in the formation of cAMP that decreased adenosine tone. This effect predominated at low mu receptor occupancy and increased the amplitude of the IPSP. Higher agonist concentrations inhibited transmitter release by both kinase-dependent and -independent pathways. This study indicates that the consequences of the morphine-induced upregulation of the cAMP cascade on synaptic transmission are dependent on the makeup of receptors and second messenger pathways present on any given terminal.

Origin of noradrenergic afferents to the shell subregion of the nucleus accumbens: anterograde and retrograde tract-tracing studies in the rat.

The nucleus accumbens (NAcc) can be subdivided into 'core' and 'shell' based on anatomical connections and histochemical markers. Previous studies have demonstrated dopamine-beta-hydroxylase immunoreactive (DBH-ir) fibers in the NAcc shell, but the source of these noradrenergic (NE) afferents has not been determined. Therefore, we have investigated in detail the anatomy of NE afferents to this subregion. Dual immunohistochemistry for DBH and substance P demonstrated numerous DBH-ir fibers in the caudal NAcc shell. Neurons projecting to the NAcc were identified with Fluoro-Gold (FG) or cholera toxin B (CTb) retrograde tracing and tyrosine hydroxylase (TH) immunohistochemistry. Single- and double-labeled neurons were observed in the A2 and A1 NE cell groups following FG injections into the caudal NAcc shell. Numerous FG and CTb single-labeled neurons were found in the rostral locus coeruleus (LC), subcoeruleus and pericoerulear dendritic region, with an occasional double-labeled neuron in the LC. Few labeled neurons were seen in the brainstem after FG injections into the NAcc core, consistent with the lack of DBH-ir in this subterritory. To confirm these results, injections of Phaseolus vulgaris leucoagglutinin or biotinylated dextran amine were made into the LC or nucleus tractus solitarius (NTS). Virtually no labeled fibers were observed in the NAcc following injections into central LC. However, fibers were observed in the NAcc shell after injections in the NTS. These results indicate that the primary source(s) of NE afferents to the NAcc shell is the A2 region of the NTS, with lesser contributions from A1 and LC.

Differential expression of glutamate decarboxylase messenger RNA in cerebellar Purkinje cells and deep cerebellar nuclei of the genetically dystonic rat.

The genetically dystonic rat exhibits a motor syndrome that closely resembles the human disease, generalized idiopathic dystonia. Although in humans dystonia is often the result of pathology in the basal ganglia, previous studies have revealed electrophysiological abnormalities and alterations in glutamate decarboxylase, the synthetic enzyme for GABA, in the cerebellum of dystonic rats. In this study, we further characterized the alterations in cerebellar GABAergic transmission in these mutants by examining the expression of the messenger RNA encoding glutamate decarboxylase (67000 mol. wt) with in situ hybridization histochemistry at the single cell level in Purkinje cells and neurons of the deep cerebellar nuclei. Glutamate decarboxylase (67000 mol. wt) messenger RNA levels were increased in the Purkinje cells and decreased in the deep cerebellar nuclei of dystonic rats compared to control littermates, suggesting opposite changes in GABAergic transmission in Purkinje cells and in their target neurons in the deep cerebellar nuclei. In contrast, levels of glutamate decarboxylase (67000 mol. wt) messenger RNA in the pallidum, and of enkephalin messenger RNA in the striatum, were unaffected in dystonic rats. The data indicate that both the Purkinje cells and GABAergic neurons of the deep cerebellar nuclei are the site of significant functional abnormality in the dystonic rat.

Effects of NMDA and its antagonists on ventral horn cholinergic neurons in organotypic roller tube spinal cord cultures.

Neurotoxic effects of excitatory amino acid (EAA) receptor agonist N-methyl-D-aspartic acid (NMDA) and its antagonists on ventral horn cholinergic neurons were studied in organotypic rollertube cultures of spinal cord (OTC-SCs) using biochemical assays of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity, and AChE histochemistry. NMDA exposure decreased ChAT and AChE activity by 83% and 66%, respectively. Cultures treated with NMDA also showed a marked loss of AChE staining in both dorsal and ventral horns and a significant, dose-dependent decrease in the number of ventral horn AChE-positive neurons (VHANs). NMDA treatment primarily resulted in the loss of small VHANs (< 300 microns2). VHANs with a size and distribution typical of alpha-motoneurons were relatively well preserved. The effects of NMDA on OTC-SCs appeared to be independent of the age of the cultures. The NMDA antagonist DL-AP5 completely prevented the NMDA-induced loss of ChAT activity, but only attenuated the effect of NMDA on ChE activity. The antagonists DL-AP5, D-AP5 and MK-801, used alone, caused significant loss and/or shrinkage of VHANs. These effects appeared to be distinct from the NMDA mediated toxicity. The results indicate that NMDA and its antagonists exert powerful toxic effects on ventral horn cholinergic neurons. The large cholinergic alpha-motoneurons, however, appear to be relatively immune to these toxic effects.

Basal ganglia and movement disorders: an update.

A model of basal ganglia functioning proposed a few years ago suggests that increased and decreased activity in basal ganglia output to the thalamus underlies akinesia, as seen in Parkinson's disease, and dyskinetic movements as seen in Huntington's disease or after treatment with L-dopa and neuroleptics, respectively. Although the basic features of this model have stood the test of time, patterns of electrophysiological activity and changes in indices of GABA-dependent transmission in the external pallidum lead to a reconsideration of the mechanisms responsible for these changes in output activity.

Effect of BSO and etanidazole on neurofilament degradation in neonatal rat spinal cord cultures.

Peripheral neuropathy is the major dose-limiting toxicity of the hypoxic cell sensitiser, etanidazole. Previous work from this laboratory using culture neuronal cell lines suggested that nitroimidazole-induced degradation of neurofilament proteins might be the critical biological event mediating this neurotoxicity. The purpose of the present study was to develop the neurofilament degradation assay in an organotypic spinal cord culture system with the goal of developing strategies for optimising sensitiser efficacy as well as ameliorating nitroimidazole-induced neurotoxicity. Spinal cord cultures were treated with etanidazole and neurofilament protein degradation was analysed by immunoblot analysis. Spinal cord cultures exposed to etanidazole exhibited a dose-dependent loss of parent neurofilament proteins, with concomitant appearance of low molecular weight degradation products. The potential neurotoxic effect of L, S-buthionine sulphoximine (BSO), a compound that enhances the radiosensitising effectiveness of 2-nitroimidazoles, was also screened in this assay system. BSO alone, at concentrations up to 100 microM, did not promote neurofilament degradation. BSO (20 microM) enhanced the effect of etanidazole on neurofilament degradation by a dose-modifying factor of 1.6 +/- 0.5. Since 20 microM BSO is expected to enhance etanidazole radiosensitisation of hypoxic cells by a larger factor, this suggests that a therapeutic gain could be achieved using BSO in combination with etanidazole in radiation therapy.

Unilateral nigrostriatal lesions induce a bilateral increase in glutamate decarboxylase messenger RNA in the reticular thalamic nucleus.

The reticular thalamic nucleus consists of densely packed neurons containing the neurotransmitter GABA. It surrounds the lateral border of the thalamus, has extensive reciprocal connections with thalamocortical neurons, and is thought to be involved in attentional processes. The reticular thalamic nucleus also receives direct and indirect inputs from the basal ganglia, suggesting that it may be involved in relaying motor information to the thalamus and cortex. We examined the possibility that decreased dopaminergic transmission in the basal ganglia indirectly affects the reticular thalamic nucleus. Rats received unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta and were killed two or three weeks after the lesion. Sections of the reticular thalamic nucleus were processed for in situ hybridization histochemistry at the single cell level with RNA probes for both isoforms of glutamate decarboxylase (M(r) 65,000: glutamate decarboxylase 65 and M(r) 67,000: glutamate decarboxylase 67), the rate limiting enzyme of GABA synthesis. Unilateral nigrostriatal dopaminergic lesions induced a topographically specific, bilateral increase in glutamate decarboxylase 67 messenger RNA in neurons of the lateral and ventral reticular thalamic nucleus. A much smaller increase in glutamate decarboxylase 65 messenger RNA was observed which was significant only ipsilateral to the lesion. Short- (seven day) and long-term (eight month) treatments with the antipsychotic drug haloperidol, in regimens that preferentially block D2 dopamine receptors, induced catalepsy and orofacial dyskinesia, respectively, but did not alter glutamate decarboxylase 67 messenger RNA levels in the reticular thalamic nucleus. Thus, loss of dopaminergic terminals, but not blockade of D2 dopamine receptors, induced the effects observed in the reticular thalamic nucleus. The results reveal a novel bilateral effect of unilateral dopamine depletion. In view of the role of the reticular thalamic nucleus in tremor and attentional processes, which are altered in Parkinson's disease, this effect may contribute to the clinical manifestations of nigrostriatal dopamine depletion.

Subthalamic nucleus lesions: widespread effects on changes in gene expression induced by nigrostriatal dopamine depletion in rats.

Lesions of the subthalamic nucleus block behavioral effects of nigrostriatal dopamine depletion in rats and primates, but the contribution of this region to the molecular effects of dopaminergic lesions is unknown. The effects of subthalamic nucleus lesions alone or in combination with a 6-hydroxydopamine-induced lesion of the substantia nigra were examined in adult rats. Unilateral subthalamic nucleus lesions caused ipsiversive rotation after peripheral administration of apomorphine and a small decrease in glutamic acid decarboxylase (GAD) mRNA in the ipsilateral globus pallidus (external pallidum). Confirming previous results, nigrostriatal dopaminergic lesions caused contraversive rotation after apomorphine injection, and increased enkephalin mRNA in the striatum, GAD mRNA in the globus pallidus, and somatostatin mRNA in the entopeduncular nucleus (internal pallidum) ipsilateral to the lesion. In addition, the lesion decreased substance P mRNA in the ipsilateral striatum compared to the contralateral side, and GAD mRNA in the contralateral entopeduncular nucleus. These effects were abolished in rats with lesions of the subthalamic nucleus and substantia nigra on the same side. Thus, the subthalamic lesions prevented changes in gene expression induced by dopamine depletion, not only in regions receiving a direct input from the subthalamic nucleus (ipsilateral pallidum), but also in regions which do not (striatum and contralateral pallidum). This suggests that polysynaptic pathways regulated by the subthalamic nucleus contribute to the effects of dopaminergic lesions in many regions of the basal ganglia. This pivotal role of the subthalamic nucleus may account for the beneficial effects of subthalamic nucleus lesions on motor symptoms resulting from dopamine depletion.

Expression of glutamic acid decarboxylase mRNA in striatum and pallidum in an animal model of tardive dyskinesia.

Long-term administration of neuroleptics can induce tardive dyskinesia in humans. Oral movements with the same distinctive form observed in humans with tardive dyskinesia are observed in rats treated with haloperidol for 8 and 12 months but not 28 days. We have examined the effects of these long-term haloperidol treatments on the levels of mRNA encoding glutamic acid decarboxylase (GAD, M(r) 67,000), the rate-limiting enzyme of GABA synthesis, in the striatum and pallidum of adult rats. Despite the differences in behavior, GAD67 mRNA was increased in the striatum and entopeduncular nucleus (internal pallidum) after both 28 days and 8 months of haloperidol administration. In contrast, only long-term haloperidol treatments (8 and 12 months) decreased GAD67 mRNA in globus pallidus (external pallidum). This effect contrasted with the increased level of GAD67 mRNA we have previously observed in the globus pallidus after short-term haloperidol treatment (3-14 days), a regimen that induces catalepsy. Together with data indicating a loss of GAD activity in target areas of the globus pallidus in humans with tardive dyskinesia, the results suggest that decreased GABAergic transmission in the projection neurons of the external pallidum may play a critical role in the motor side effects associated with long-term neuroleptic therapy.

Glutamate decarboxylase messenger RNA in rat pallidum: comparison of the effects of haloperidol, clozapine and combined haloperidol-scopolamine treatments.

We have investigated the effects of neuroleptic treatments which do, or do not, induce catalepsy on the level of expression of glutamate decarboxylase, the rate limiting enzyme in GABA synthesis, in efferent neurons of the pallidum in adult rats. Different regimens of haloperidol (1 mg/kg s.c., three, seven or 14 days; 2 mg/kg, s.c., 10 days) induced catalepsy in a majority of rats and increased glutamate decarboxylase messenger RNA levels in the globus pallidus (external pallidum) in those rats exhibiting catalepsy. Levels of glutamate decarboxylase messenger RNA were also increased in the entopeduncular nucleus (internal pallidum), but only after 14 days of treatment with haloperidol. The atypical antipsychotic clozapine (seven days, 20 mg/kg, s.c.), which did not induce catalepsy, slightly decreased glutamate decarboxylase messenger RNA levels in the globus pallidus. When co-administered with haloperidol (seven days, 1 mg/kg s.c.), the muscarinic antagonist scopolamine (1 mg/kg, s.c.) completely blocked both haloperidol-induced catalepsy and increases in glutamate decarboxylase messenger RNA levels in the globus pallidus. In contrast, scopolamine was not able to block increased glutamate decarboxylase and enkephalin messenger RNA expression induced by haloperidol in the striatum. These results reveal a good correlation between increases in glutamate decarboxylase messenger RNA levels in the globus pallidus and catalepsy after these drug treatments and suggest that anticholinergic blockade of the behavioral and molecular effects of neuroleptics may involve non-striatal mechanisms.

Regulation of mu-opioid receptor mRNA in rat globus pallidus: effects of enkephalin increases induced by short- and long-term haloperidol administration.

The mRNA encoding mu-opioid receptors is expressed in neurons of the globus pallidus, a region of the basal ganglia that receives a dense enkephalinergic innervation from the striatum. The regulation of the mRNAs encoding the opioid peptide enkephalin in the striatum and the mu-opioid receptor in the globus pallidus was examined with in situ hybridization histochemistry following short- or long-term haloperidol treatments, which alter striatal enkephalin mRNA levels. Animals were administered haloperidol daily for 3 or 7 days (1 mg/kg, s.c.) or continuously for 8 months (1 mg/kg, depot followed by oral). Enkephalin and mu-opioid receptor mRNA levels were unchanged after 3 days of haloperidol treatment. In contrast, the enkephalin mRNA level was increased in the striatum, and mu-opioid receptor mRNA levels were markedly decreased in the globus pallidus after 7 days of haloperidol administration. Similar effects were observed in rats treated with haloperidol for 8 months. The results provide the first evidence of regulation of mu-opioid receptor mRNA in vivo.

Expression of mu opioid receptor mRNA in rat brain: an in situ hybridization study at the single cell level.

The mu (mu) opioid receptors, which mediate the effects of morphine, are widely distributed in brain. We have examined the distribution of mRNA encoding a mu opioid receptor in rat brain with in situ hybridization histochemistry at the single-cell level to obtain information about the cell types synthesizing this receptor. Only neurons, not glia, were labeled in discrete brain regions. High levels of labeling were detected in the thalamus, striosomes of the caudate-putamen, globus pallidus, and brain regions involved in nociception, arousal, respiratory control, and, possibly, addiction. The general distribution of the receptor mRNA paralleled that of mu opioid binding sites with some notable exceptions. These include the cerebral cortex, which contains binding sites, but very few labeled neurons. No labeling was observed in the cerebellum, a region devoid of mu binding sites. Three main findings emerged from these experiments: 1) the mRNA was present in regions mediating both the therapeutic (analgesia) and the unwanted (respiratory depression, addiction) effects of morphine, 2) the mRNA was very densely expressed by neurons known to receive dense enkephalin-containing inputs, and 3) the dissociation between the presence of binding sites and absence of mRNA in some brain regions supports a presynaptic localization of mu opioid receptors in these areas. Alternatively, other subtypes of mu opioid receptors may be encoded by a different mRNA. These results provide new insights into the receptor types and neuronal circuits involved in the effects of endogenous opioids and morphine.

Excitatory amino acid receptors mediate the orofacial stereotypy elicited by dopaminergic stimulation of the ventrolateral striatum.

The present experiments examined the role of excitatory amino acid receptors in the orofacial stereotypy induced by direct amphetamine microinjection into the ventrolateral striatum. In these experiments, the influence of prior intra-ventrolateral striatum treatment with various excitatory amino acid antagonists on the expression of amphetamine-stimulated oral stereotypy was observed. In all experiments, behavioral observations were conducted in the home cage using a time-sampling procedure. In the first experiment, different groups of rats received bilateral microinfusions of either kynurenic acid, 2-amino-5-phosphonopentanoic acid, 6,7-dinitroquinoxaline or dizocilpine maleate. The excitatory amino acid antagonists were administered immediately prior to bilateral microinfusions of d-amphetamine. Both N-methyl-D-aspartate and non-N-methyl-D-aspartate antagonists dose-dependently attenuated or blocked the expression of dopamine-mediated stereotypy. 2-Amino-5-phosphonopentanoic acid was the most potent of these compounds, totally suppressing stereotypy at a dose of 0.3 micrograms (equivalent to 1.5 nmol). In the second experiment, the same compounds were tested for their ability to suppress physostigmine-induced mouth movements. Cholinergic stimulation of the ventrolateral striatum has previously been shown to elicit non-directed mouth movements, quite distinguishable from stimulus-directed, amphetamine-induced biting. Excitatory amino acid antagonists were administered in the same doses prior to bilateral infusion of physostigmine (2.5 micrograms/0.5 microliters). The expression of physostigmine-induced mouth movements was for the most part not affected by excitatory amino acid antagonists, although dizocilpine maleate slightly reduced this oral behavior. In a third experiment, behavior was observed following infusion of the antagonists alone, using the same doses as in the previous experiments. No behavioral alterations were observed with the exception of a small increase in nonspecific mouth movements induced by kynurenic acid and 2-amino-5-phosphonopentanoic acid. These findings indicate that the expression of dopamine-mediated oral stereotypy, induced by amphetamine stimulation of the ventrolateral striatal region, is highly dependent on activation of striatal excitatory amino acid receptors. In contrast, oral behavior induced by cholinergic stimulation of the ventrolateral region is not mediated by glutamate input. These results are discussed in relation to the synaptic organization of neuronal elements within the striatum. Moreover, the relevance to further understanding of orofacial dyskinesias is noted.

Modification of the aerobic cytotoxicity of etanidazole.

PURPOSE: To determine the feasibility of modifying the aerobic cytotoxicity of etanidazole without interfering with the tumoricidal action of radiation plus etanidazole. METHODS AND MATERIALS: The aerobic cytotoxicity of etanidazole was studied using two different models: (1) Induction of apoptosis in EL4 cells: apoptotic DNA fragmentation was analyzed by agarose gel electrophoresis following 24 h treatment with etanidazole alone or in combination with various modifiers. (2) Spinal cord neuronal loss in organotypic roller tube cultures: Survival of acetylcholinesterase positive ventral horn neurons was analyzed morphometrically following 72 h treatment with etanidazole alone or in combination with vitamin E succinate. RESULTS: Etanidazole (10 mM) induced apoptosis in EL4 cells. This effect was suppressed by 24 h treatment with TPA, IBMX, the free radical scavenger TEMPOL or vitamin E succinate. Vitamin E succinate also protected spinal cord cultures from etanidazole-induced neuronal loss. CONCLUSION: These results suggest that it might be possible to modify the neurotoxicity of etanidazole with agents that would not be expected to interfere with the tumoricidal action of radiation plus etanidazole.