Central noradrenaline depletion antagonizes aspects of d-amphetamine-induced hyperactivity in the rat

The effects of noradrenaline (NA) depletion upon amphetamine-induced hyperactivity were examined in five experiments. Central NA depletion via either systemic DSP4 or neonatal 6-OHDA antagonised the amphetamine-induced (2 mg/kg SC) increase in rearing behaviour, whereas lesions of the dorsal noradrenergic bundle using 6-hydroxydopamine antagonised the increase in locomotor activity. Peripheral NA depletion following systemic 6-hydroxydopamine to adult rats did not cause any changes in motor activity after acute amphetamine administration. Desipramine, the selective NA uptake inhibitor, blocked the effects of DSP4 upon amphetamine-induced rearing. NA depletion antagonised hyperactivity produced by the 2 mg/kg dose of amphetamine, but not the hyperactivity (rearing or locomotion) effects of amphetamine at 1, 4 or 8 mg/kg.

Astroglial development in microencephalic rat brain after fetal methylazoxymethanol treatment

Treatment of pregnant rats on gestation day 15 with methylazoxymethanol (MAM) leads to a marked microencephaly in the offspring with a considerable atrophy in cerebral cortex, hippocampus and striatum. The development of the astrocytic populations in these atrophic regions was studied by means of immunohistochemistry using an antiserum against glial fibrillary acidic protein (GFA). The distribution and density of GFA-positive structures were not notably altered in the parietal cortex, hippocampal formation and striatum after prenatal MAM-treatment as compared to control. Also the individual astrocytes were morphologically similar in experimental and control animals in all regions analyzed. We suggest that an adjustment of the astrocytic development has occurred in response to the changed neuronal environment. Alternatively, MAM-treatment may affect neuronal and glial precursor cells leading to a seemingly normal astrocytic cell density.

Determination of catecholamines in tissue and body fluids using microbore HPLC with amperometric detection

Performance of microbore reverse phase HPLC coupled with amperometric detection is detailed for the analysis of catecholamines in small tissue samples and human blood plasma and cerebrospinal fluid. Extraction procedures for pre-concentration and clean-up of these samples are described. Marked signal enhancement is observed due to the smaller column volume as well as the increased coulometric yield which results from the lower flow rates used with this technique. Detection limits of 0.2 to 0.5 picograms are obtained allowing analysis of catecholamines in extremely small tissue samples or small volumes of cerebrospinal fluid or plasma.

The hindlimb extension reflex is not a reliable marker of post-decapitation convulsions or spinal noradrenaline depletion in rats

The degree of hindlimb extension reflex (ER), post-decapitation reflex (PDR) and noradrenaline (NA) depletion was measured under various treatment regimens involving the neurotoxins DSP4 and 6-OHDA. Neither neonatal 6-OHDA treatment, direct application of 6-OHDA to the locus coeruleus nor DSP4 treatment produced a blockade of ER that could be associated with the loss of PDR and the spinal NA depletion, whereas intrathecal 6-OHDA treatment caused a strong loss of both ER and PDR related to severe spinal NA depletion. No correlation was obtained between the ER and PDR in a large number of DSP4-treated rats.

Electrophysiological and neurochemical correlates of the neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on central catecholamine neurons in the mouse

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is an agent which produces a parkinsonian syndrome in man. To explore the use of MPTP in a rodent model of parkinsonism, male albino mice (NMRI) were given MPTP (50 mg/kg, s.c.) twice with a 6-8 h interval. Up to 10 weeks after injection, mice were killed and high-pressure liquid chromatography was used to assay dopamine (DA) and noradrenaline (NA) concentrations in various regions of the CNS. At 4 and 10 weeks after injection, DA levels were significantly reduced in occipital cortex (-40%), hippocampus (-30%), and striatum (-60%). NA levels were reduced by 60-80% in frontal and occipital cortex, hippocampus, and cerebellum. Neither DA nor NA concentration was reduced in spinal cord. Dopaminergic denervation was also suggested by electrophysiological data which showed that treatment with MPTP increased the spontaneous discharge rate of caudate neurons and decreased the potency of locally administered phencyclidine, an indirect DA agonist. However, denervation was evidently not complete enough to produce postsynaptic receptor supersensitivity, as MPTP treatment did not increase the potency of locally applied DA, and it did not increase 3H-spiperone binding in striatal membrane preparations. These results suggest that MPTP causes regionally selective and long-term reductions of catecholamine transmission in the CNS of the mouse.

Dopaminergic neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the mouse: an in vivo electrochemical study

The long-term (i.e., 4-5 months) effects of large doses (3 X 50 mg/kg) of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on striatal dopamine-containing afferents were studied in the NMRI strain of mice. Recently improved in vivo electrochemical methods were first used to examine the magnitude, spatial distribution and temporal dynamics of monoamine release initiated via local application of potassium in various regions of the mouse striatum. Immunohistochemical localization of tyrosine hydroxylase and computer-based image analysis were also used to quantitate regional catecholamine-containing nerve fiber densities in the caudate nucleus. The in vivo electrochemical studies showed a statistically significant decrease in the average potassium-evoked release of electroactive species from the MPTP-treated mouse caudate nucleus vs. control. Greater decreases in release were seen in dorsal than in ventral striatum (55% vs. 33%). The average rise time of potassium-evoked release was also significantly prolonged (greater than 50%) after MPTP pretreatment. Histochemical studies showed an overall reduction in the density of dopamine-containing terminals in the drug-treated mice, with a greater loss observed in the more dorsal regions of the caudate nucleus. The experimental data thus support a long-term selective destruction of dorsal vs. ventral dopamine-containing afferents to the striatum by the neurotoxin MPTP in mice.

Complete blockade and attenuation of 5-hydroxytryptamine induced analgesia following NA depletion in rats and mice

The effect of pretreatment with the noradrenaline neurotoxin, N-2-chloroethyl-N-ethyl-2-bromobenzylamine (DSP4), upon the analgesia induced by various doses of 5-hydroxytryptamine (5-HT) was examined in rats and mice. DSP4 treatment (2 X 50 mg/kg, intraperitoneally) of rats caused a complete blockade of 5-HT induced analgesia in the tail-flick, hot-plate and shock titration tests. DSP4 treatment (1 X 50 mg/kg, intraperitoneally) of mice caused a partial blockade of 5-HT induced analgesia in the hot-plate test, but no significant blockade in the tail-flick test. These results are discussed with regard to serotonergic-noradrenergic interactions and the species discrepancy in nociceptive testing.

Deficits in behavioral initiation and execution processes in monkeys with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced parkinsonism

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to two monkeys led to hypokinesia, tremor, rigidity, adipsia and aphagia. Quantitative assessment of hypokinesia revealed increased reaction time, delayed onset of muscle activity and prolonged movement time in a forelimb reaching task after selective degeneration of the nigrostriatal dopamine (DA) system sparing mesocortical dopamine neurons. The losses of pars compacta cells of substantia nigra, of striatal [3H]mazindol binding and of striatal DA content (more than 90%) quantitatively paralleled the severity of behavioral deficits. Additional monoamine systems were affected with stronger MPTP effects.

Noradrenaline depletion increases noradrenaline-induced antinociception in mice

Mice were treated with N-2-chloroethyl-N-ethyl-2-bromobenzylamine hydrochloride (DSP4), which causes severe noradrenaline (NA) depletions in brain regions and the spinal cord, or vehicle i.p. They were tested 14 days later for antinociception induced by intrathecal injections of different doses of NA. A potentiation of the NA effect upon pain sensitivity was observed, with both an increase in the magnitude and duration of the antinociceptive responses. Upon biochemical analysis of spinal cords, it was found that DSP4-treated mice had a 80% depletion of NA, whereas dopamine and 5-hydroxytryptamine were unaffected. Radioligand binding of [3H]clonidine in membranes prepared from spinal cord, showed no differences in density of alpha 2-adrenoceptors, but the affinity had been increased, probably explaining the supersensitivity.

Active and passive avoidance following the administration of systemic DSP4, xylamine, or p-chloroamphetamine

Groups of rats were administered either DSP4 (50 mg/kg, ip), xylamine (50 mg/kg, ip), or p-chloroamphetamine (2 X 10 mg/kg, ip), either 2 weeks or 1 week before the testing of two-way active avoidance. DSP4 and xylamine, the selective noradrenaline (NA) neurotoxins, caused a two-way avoidance impairment but p-chloroamphetamine, the selective 5-hydroxytryptamine (5-HT) neurotoxin, did not do so. Pretreatment with desipramine (20 mg/kg, ip) blocked the avoidance impairment caused by DSP4 and xylamine treatment. Neither DSP4 nor xylamine caused any alteration of passive avoidance retention. The biochemical analyses indicated severe NA, but not 5-HT, depletions in the DSP4 and xylamine conditions and drastic 5-HT, but not NA, depletions in the p-chloroamphetamine conditions. These results confirm and extend earlier findings concerning the role of NA in avoidance behavior.

Pharmacological interference with the neurotoxic action of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on central catecholamine neurons in the mouse

The effect of pretreatment with various MAO and catecholamine uptake inhibitors on the MPTP-induced reduction of endogenous catecholamine levels and [3H]catecholamine uptake in mouse striatum and cerebral cortex associated with the neurotoxic action of MPTP on dopamine and noradrenaline neurons was investigated. Pargyline and deprenyl almost completely reversed the MPTP-induced reduction of these parameters in both regions while chlorgyline was without effect. Pretreatment with the dopamine uptake inhibitor amfolenic acid preferentially counteracted the depleting effect of MPTP on striatal dopamine levels. The noradrenaline uptake inhibitors desipramine, nortriptyline and LY 139603 all antagonized the MPTP-induced reduction of noradrenaline levels in cerebral cortex, while none of these inhibitors affected the action of MPTP on striatal dopamine. The results suggest that MAO-B and the catecholamine uptake system may be critically involved at certain steps in the neurotoxic action of MPTP on catecholamine neurons. The interaction with the uptake mechanism most likely explains the selective neurotoxic action of MPTP on catecholamine neurons.

Flexor tenosynovitis (FTS): a risk indicator of abnormal glucose tolerance

Diabetes mellitus (DM), particularly of long duration and insulin dependent, can be accompanied by a variety of locomotor system disorders. However, musculo-skeletal syndromes can also appear in patients with mild glucose homeostasis disturbances. Sometimes these locomotor complaints may precede the diagnosis of the deranged glucose metabolism and hence give a clue to the underlying glucose homeostasis abnormality. In the present work, glucose metabolism was studied in 39 patients presenting with palmar flexor tenosynovitis (FTS) but without any other rheumatic manifestations. For comparison, glucose homeostasis was also studied in 44 patients with FTS accompanying rheumatoid arthritis (RA). In the first group, 23% had an abnormal oral glucose tolerance test (OGTT), a significantly increased frequency vis-à-vis the 4.5% found in the RA group and vis-à-vis the 5.4% reported for the general population. It is concluded that in the absence of any other rheumatic disease, FTS is a risk indicator of disturbed glucose metabolism and that a simple screening procedure for the purpose of disclosing glucose homeostasis abnormalities is warranted in patients presenting with FTS.

Neurochemical and histochemical characterization of neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine on brain catecholamine neurones in the mouse

Systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) caused a rapid and long-lasting reduction of both 3,4-dihydroxyphenylalanine (dopamine, DA) and noradrenaline (NA) in mouse brain, as observed histo- and neurochemically. The depleting effects were more pronounced after repeated MPTP administration and the most marked reductions were observed after 2 X 50 mg MPTP/kg s.c., when DA in striatum and NA in frontal cortex were reduced by greater than 90% 1 week after MPTP. Mice with such catecholamine depletions were markedly sedated and almost completely immobilized. The behavioural syndrome after MPTP resembled that seen after reserpine, a monoamine-depleting drug. MPTP also caused a long-lasting reduction of catecholamine uptake in striatal DA and cortical NA nerve terminals and reduced tyrosine hydroxylase activity in these regions. There was no evidence that MPTP caused any marked DA and NA cell body death. MPTP given acutely transiently elevated serotonin levels. The results are compatible with a neurotoxic action of MPTP on both DA and NA nerve terminals. The nigro-striatal DA and the locus coeruleus NA neurone systems appeared to be most susceptible. Synthesis and utilization of residual striatal DA and cortical NA were increased, as often observed in partially denervated monoamine-innervated brain regions. Both DA and NA showed a gradual recovery, which took months to become complete and may have been related to a regrowth of catecholamine nerve terminals.

GM1 ganglioside enhances regrowth of noradrenaline nerve terminals in rat cerebral cortex lesioned by the neurotoxin 6-hydroxydopamine

The effect of exogenous GM1 ganglioside on selectively noradrenaline-denervated rat cerebral cortex was investigated by measuring the spatial distribution of endogenous noradrenaline levels and by fluorescence histochemical analysis. A local noradrenaline denervation was produced by intracortical infusion of the selective catecholamine neurotoxin 6-hydroxydopamine for 3 or 7 days. The neurotoxin infusion caused an almost complete noradrenaline denervation in a restricted area around the infusion point as reflected by an almost complete long-term disappearance of noradrenaline nerve terminals and reduction of noradrenaline levels. There was with time a slow recovery of the levels, most likely related to a spontaneous noradrenaline nerve terminal regeneration. Post-treatment for 1 week with GM1 had very small effects on the 6-hydroxydopamine-induced reduction of the noradrenaline levels, while pretreatment with GM1 for 3 days before the neurotoxin infusion and continuing the GM1 administration for another 7-14 days significantly enhanced noradrenaline recovery, as observed both bio- and histochemically. GM1 had no effect on the 6-hydroxydopamine-induced noradrenaline depletion acutely, indicating that GM1 does not interfere with the direct neurotoxic actions of 6-hydroxydopamine. The present results thus indicate that exogenous GM1 enhances regrowth of noradrenaline nerve terminals which may be due to a regrowth stimulatory effect (regeneration/collateral sprouting) and/or related to protective actions of GM1 against retrograde degeneration of noradrenaline axons following the neurotoxin-induced lesion.

Effect of GM1 ganglioside on neonatally neurotoxin induced degeneration of serotonin neurons in the rat brain

The effect of exogenous GM1 ganglioside on the 5,7-dihydroxytryptamine (5,7-HT; a selective serotonin neurotoxin) induced alteration of the postnatal development of central 5-hydroxytryptamine (5-HT; serotonin) neurons has been investigated using neuro-chemical and immunocytochemical techniques. Neonatal 5,7-HT (50 mg/kg s.c.) treatment is known to lead to a marked and a permanent degeneration of distant 5-HT nerve terminal projections (e.g. in cerebral cortex, hippocampus and spinal cord), while projections close to the 5-HT perikarya in the mesencephalon and pons-medulla increase their nerve density. These regional alterations are reflected by decreases and increases, respectively, of endogenous 5-HT, [3H]5-HT uptake in vitro and number of 5-HT nerve terminals demonstrated by immunocytochemistry. Treatment of newborn rats with GM1 (4 X 30 mg/kg s.c.; 24 h interval) had no significant effect on the postnatal development of 5-HT neurons. GM1 administration had furthermore no effect on the 5,7-HT induced alteration of the regional 5-HT levels and [3H]5-HT uptake in the cerebral cortex acutely, indicating that GM1 did not significantly interfere with the primary neurodegenerative actions of 5,7-HT. At the age of 1 month a clear counteracting effect of GM1 was observed, in particular of the 5,7-HT induced 5-HT denervations. The 5-HT levels in the frontal and occipital cortex were reduced to 25 and 20% of control after 5,7-HT alone, while these values were 70 and 40%, respectively, after 5,7-HT and GM1 treatment. A similar antagonizing effect of GM1 was found in the frontal cortex when measuring [3H]5-HT uptake. GM1 treatment also caused a minor reduction of the 5,7-HT induced increase of the 5-HT levels in striatum and mesencephalon. Quantitation of 5-HT nerve terminal density in sections processed for 5-HT immunocytochemistry using an automatic image analysis system showed markedly more nerve terminals in the frontal and occipital cortex after 5,7-HT + GM1 compared to 5,7-HT treatment alone. Minor counteracting effects of GM1 were noted in the hippocampus and spinal cord (thoracic-lumbar) as evaluated by chemical 5-HT assay, although substantial counteracting effects were observed locally in these areas by quantitative immunocytochemistry.(ABSTRACT TRUNCATED AT 400 WORDS)

Monoamine neurotransmitter metabolism in microencephalic rat brain after prenatal methylazoxymethanol treatment

Administration of methylazoxymethanol (MAM) in the fetal stage leads to forebrain microencephaly with a severe atrophy in cerebral cortex, striatum, and hippocampus. The concentration of endogenous monoamines was markedly increased in the atrophic regions while total amount was largely unchanged. Striatal dopamine and cortical noradrenaline nerve terminals from MAM treated animals showed unaltered sedimentation properties in a sucrose density gradient and were estimated to have normal transmitter levels. gamma-Butyrolactone induced increase in dopamine levels and its counteraction by apomorphine was essentially unaltered after MAM. These data give further support for the view that the monoamine nerve terminal fields develop to their normal size in the atrophic regions leading to a hyperinnervation. Analysis of monoamine metabolite levels, increase of monoamines after monoamine oxidase inhibition, and disappearance of catecholamines after tyrosine hydroxylase inhibition were conducted to obtain information on monoamine turnover. The results indicated an essentially unaltered, or a small reduction of, monoamine turnover in the atrophic regions when calculated per monoamine nerve terminal, while increased when calculated per unit weight of the tissue.

Pharmacological modifications of the neurotoxic action of the noradrenaline neurotoxin DSP4 on central noradrenaline neurons

Systemic treatment with the noradrenaline neurotoxin DSP4 (N-[2-chloroethyl]-N-ethyl-2-bromobenzylamine; 7 days) led to a marked and quantitatively similar reduction (-80%) of endogenous noradrenaline, [3H]noradrenaline uptake in vitro and [3H]desipramine binding in the frontal cortex of adult rats. Inhibition of monoamine oxidase, and/or 1-dopa administration 1 week after DSP4 produced very small changes in brain noradrenaline and dopamine levels. These results are all consistent with the view that DSP4 produces an acute and selective degeneration of central noradrenaline nerve terminals. Pretreatment with the noradrenaline uptake blocker desipramine prevented the action of DSP4 almost completely, while treatment after DSP4 had minute effects on DSP4-induced reduction of endogenous noradrenaline and [3H]noradrenaline uptake. The data suggest that the irreversible neurotoxic actions of DSP4 are very rapid and largely complete within 0.5 h after DSP4 administration. Measurement of catecholamine turnover using monoamine oxidase inhibition by pargyline indicated an increased noradrenaline turnover in the remaining nerve terminals innervating cerebral cortex and hippocampus after DSP4, while dopamine turnover appeared to be decreased. Pretreatment with d-amphetamine and clonidine or subsequent treatment with oxotremorine were without effect on the DSP4-induced reductions of the regional brain noradrenaline levels. Morphine pretreatment was also ineffective, while repeated morphine administration after DSP4 produced a significant potentiation of the DSP4-induced noradrenaline depletion in the frontal cortex, cerebellum and the spinal cord. Pretreatment with the monoamine oxidase inhibitor pargyline led to a very pronounced counteraction of the DSP4-induced noradrenaline depletion in all brain regions analysed, in particular in the occipital cortex. The data suggest that morphine can potentiate the neurotoxic action of DSP4 while pargyline can counteract it.

Effects of the noradrenaline neurotoxin DSP 4 on monoamine neurons and their transmitter turnover in rat CNS

Regional effects of DSP 4 on monoamine neurons have been analyzed by chemical assay of endogenous monoamines and their metabolites in rat CNS. The results confirmed that the neurotoxic action of DSP 4 is predominantly on noradrenaline nerve terminal projections originating from locus coeruleus, with the most marked effects on terminal fields localized most distant from the noradrenaline perikarya. DSP 4 treatment (10 days) caused no alteration of the regional DA levels, except in cingulate cortex, where a moderate increase (+40%) was observed, possibly at least partially related to a sprouting of dopamine nerve terminals following the noradrenaline denervation. 5-hydroxytryptamine levels were generally unaltered after DSP 4, except for an about 10-25% reduction in cerebral cortex and hippocampus. There was with time a certain noradrenaline recovery, most likely related to regeneration of noradrenaline nerve terminals, although this process was relatively slow (months). Analysis of catecholamine decline after tyrosine hydroxylase inhibition and metabolite/monoamine ratios, as indices for transmitter utilization rate, indicated an increased noradrenaline turnover in terminals spared by DSP 4, while dopamine turnover appeared to be reduced in many regions (i.a. cerebral cortex, striatum, accumbens, olfactory tubercle and spinal cord), most pronounced in cingulate cortex. The results indicate that noradrenaline neurons have a facilitatory action on dopamine neurons. The DSP 4 treatment did not cause any significant effect on 5-hydroxytryptamine turnover in any of the individual regions analyzed.

Role of olfactory bulbectomy and DSP4 treatment in avoidance learning in the rat

Olfactory bulbectomized rats and DSP4-treated rats were studied on a two-way active avoidance task as well as on step-down passive avoidance and fear conditioning and retention tasks in three experiments. The DSP4-treated, but not olfactory bulbectomized, rats were impaired in acquiring two-way avoidance; bulbectomized, but not DSP4-treated, rats were found to show notable passive avoidance and fear retention deficits. Bulbectomized rats treated with DSP4 did not show passive avoidance and fear retention deficits, nor did these animals evidence the two-way avoidance impairment of the DSP4-treated rats. No alteration of dopamine-beta-hydroxylase activity in the frontal cortex and hippocampus as a result of the bulbectomy operation was indicated. The double dissociation between bulbectomized and DSP4-treated rats is discussed in terms of opponent behavioral processes, influenced by olfactory bulbectomy and DSP4, which may permit insights into experimental investigations of stress, anxiety, and depression.

A parametric study of the effects of the noradrenaline neurotoxin DSP4 on avoidance acquisition and noradrenaline neurones in the CNS of the rat

The effects of various doses of DSP4 on two-way active avoidance acquisition in rats and on central noradrenaline neurones were compared. Doses of DSP4 from 3 mg kg-1 i.p. and upwards injected one week before the onset of the avoidance trials significantly impaired two-way avoidance learning. The learning impairment caused by DSP4 (50 mg kg-1 i.p.) lasted for at least 10 weeks. Desipramine (20 mg kg-1) injected either 30 or 60 min before DSP4 (50 mg kg-1) antagonized the active avoidance impairment. A high dose of DSP4 (50 mg kg-1 i.p.) produced profound decreases in dopamine-beta-hydroxylase activity in the frontal cortex and in the concentrations of noradrenaline in various brain regions indicating degeneration of the locus coeruleus noradrenaline system. Low doses of DSP4 (3 and 6 mg kg-1 i.p.) produced small but significant decrease in the concentrations of noradrenaline (NA) in some regions, e.g. cerebral cortex, hippocampus, olfactory bulb and spinal cord. The avoidance impairment caused by the low dose of DSP4 (3 mg kg-1) was absent when rats were tested 10 weeks after treatment nor was NA depletion present when NA was analysed 3 months after treatment.

Measurement of 5-hydroxytryptophol and 5-hydroxyindoleacetic acid in human and rat brain and plasma

The levels of 5-hydroxyindoleacetic acid (5-HIAA) and free and total 5-hydroxytryptophol (5-HTOL) in human and rat brain regions and plasma were determined by a specific capillary column gas chromatographic--mass spectrometric method. The human brains were obtained 2-3 hours post mortem, and the levels of 5-HIAA were in the range of 0.48-31.3 nmoles/g in the regions investigated. The levels of free and total 5-HTOL were 10.9-387 pmoles/g and 14.5-821 pmoles/g, respectively. The ratio of total 5-HTOL to 5-HIAA was in the range of 0.6-5.5%. In human plasma the levels of free and total 5-HTOL were 0.9 +/- 0.3 and 2.9 +/- 0.8 pmoles/ml +/- S.E.M., respectively. In regions of rat brain, the 5-HIAA levels ranged from 0.37-2.84 nmoles/g. Free and total 5-HTOL were in the range of 11.4-56.1 and 16.2-77.1 pmoles/g, respectively. The ratio of total 5-HTOL and 5-HIAA ranged from 2.3-5.1%. Higher levels of 5-HIAA and 5-HTOL occurred in the rat pineal gland. In rat plasma the levels of free and total 5-HTOL were 1.34 +/- 0.06 and 21.6 +/- 1.6 pmoles/ml +/- S.E.M., respectively.

Neurotoxicity of the meperidine analogue N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine on brain catecholamine neurons in the mouse

The effect of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (NMPTP) on central monoamine neurons in mice was investigated using histo- and biochemical techniques. NMPTP (2 X 10 mg/kg i.v.) produced a rapid and long-lasting reduction (-30%) of striatal dopamine, while the dopamine levels were only transiently reduced in mesencephalon and frontal cortex. HVA and DOPAC were initially markedly reduced (-50 to -70%) in striatum while a marked recovery was found in the chronic stage. NMPTP also induced a long-term reduction of noradrenaline in striatum and frontal cortex while 5-hydroxytryptamine and 5-HIAA levels were essentially unaltered. The data indicate a neurotoxic action of NMPTP on both dopamine and noradrenaline nerve terminals in mouse brain.