Co-administration of memantine and amantadine with sub/suprathreshold doses of L-Dopa restores motor behaviour of MPTP-treated mice

The antiparkinsonian effects of the uncompetitive NMDA antagonists, memantine, amantadine and MK-801, in combination with an acute subthreshold dose of L-Dopa (5 mg/kg) in drug-naive MPTP-treated mice or a suprathreshold dose (20 mg/kg) in L-Dopa tolerant MPTP-treated mice were investigated. In the former case, memantine (locomotion: 3 mg/kg; rearing: 1 mg/kg) and amantadine (locomotion and rearing: 10 mg/kg) injected 60 min before the subthreshold dose of L-Dopa (5 mg/kg), each induced an antiparkinsonian action in hypokinesic MPTP-treated mice that consisted of dose-specific, as opposed to dose-related, elevations of locomotion and rearing behaviour. At the same time, higher doses of memantine reduced further the rearing (10 and 30 mg/kg) and locomotor (30mg/kg) behaviour of the MPTP-treated mice. MK-801 plus L-Dopa elevated locomotion (0.1 mg/kg) but reduced rearing at the 0.3 mg/kg dose. In control, saline-treated mice, memantine (3, 10 and 30 mg/kg) and MK-801 (0.1 and 0.3 mg/kg) increased locomotor behaviour but decreased rearing behaviour, while amantadine produced no effects. Memantine increased locomotor (1 and 3 mg/kg, s.c.; 1 mg/kg dose restored activity) and rearing (0.3 and 3 mg/kg) activity in the L-Dopa tolerant MPTP-treated mice, whereas amantadine (3 and 10 mg/kg) restored both locomotor (30 mg/kg significantly increased locomotion but did not restore the activity level) and rearing (3 mg/kg only) activity. MK-801 (0.1 and 0.3 mg/kg, s.c.) also increased significantly locomotor activity of L-Dopa-tolerant MPTP mice although the antikinetic action was not reversed, thereby precluding a restorative effect of the compound. These results, demonstrating both a synergistic and a restorative effect of the NMDA antagonists in coadministration with L-Dopa, demonstrate a putative antiparkinson action by these compounds in a functional animal model that incorporates the "wearing-off" complications of L-Dopa administration in the disorder.

Effects of MAO inhibitors upon MPTP mice chronically treated with suprathreshold doses of L-dopa

Groups of mice were administered either saline or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (2 X 40 mg / kg, s.c., separated by a 24-hour interval) 4-6 weeks prior to behavioural testing. At testing, all the MPTP-injected mice were repeatedly administered L-dopa (20 mg / kg, s.c., five times each week, Monday-Friday), by applying a procedure that induced a severe reduction of motor activity parameters from Day 1 to Day 25. Control (uninjected mice) received only saline and were retained only for neurochemical analysis. In each of three experiments, following the reduction of the activity-stimulating effects of L-dopa by repeated administration, a restorative effect of different monoamine oxidase (MAO) inhibitors was tested by co-administration of the test compounds (irreversible MAO-B inhibitor, reversible MAO-A inhibitors, or irreversible MAO-A / mixed MAO inhibitors) with L-dopa (20 mg / kg). In each case the MAO inhibitor was injected 60 min prior to L-dopa. L-Deprenyl (3 or 10 mg / kg, s.c.), in combination with L-dopa, reinstated locomotion and total activity, but not rearing, dose-dependently, in L-dopa-tolerant mice. The reversible MAO-A inhibitors, amiflamine and alpha-ethyltryptamine, in combination with L-dopa, reinstated locomotion and total activity, leaving rearing unaffected; Ro 41-1049 (3 mg / kg, s.c.) restored all three parameters of activity; locomotor activity was restored by all three doses (1, 3, and 10 mg / kg, s.c.). On the other hand, neither the irreversible MAO-A inhibitor, clorgyline, nor the mixed MAO inhibitor, phenelzine, produced any directly effective restorative increments. Neurochemical analysis confirmed the severe striatal dopamine depletion of MPTP-treated mice. These results demonstrate a synergistic and restorative action of combining certain MAO inhibitors, namely the reversible MAO-A inhibitors, with the suprathreshold dose of L-dopa in MPTP-treated, L-dopa-tolerant mice.

Neonatal nicotine administration influences ethanol-induced behaviors

Neonatal mice were administered nicotine (66 microg (-)-nicotine base/kg body weight (bw) s.c. twice daily at 0800 and 1700 h on postnatal days 10 and 14) and control mice received saline (10 ml 0. 9% NaCl/kg bw s.c.) on the same occasions. Behavioral testing was initiated 3 months after birth. In Experiment 1, neonatal nicotine administration did not affect spontaneous motor activity but altered the peak dose stimulatory effect of ethanol upon locomotion and rearing activity from 3.0 mg/kg, in the control mice, to 1.5 mg/kg. Administration of the nicotine antagonist, mecamylamine (MEC, 2.0 mg/kg), had no effect upon the peak dose stimulatory effect (i.e., 1. 5 mg/kg) evidenced in the nicotine-treated mice, but attenuated the stimulatory effect of the 3.0 mg/kg dose of ethanol in the control mice. In Experiment 2, the effects of neonatal nicotine administration upon ethanol intake and preference were assessed. In the single fluid access (one-bottle) test, nicotine-treated mice consumed both more ethanol (2%, 4%, or 6% concentrations) and more tap water than control mice. In the two-bottle ethanol preference test, nicotine-treated mice consumed more ethanol and tap water. Further analysis of the high-preferring (HP) ethanol mice indicated higher ethanol intake and preference in the nicotine-treated mice but no differences in tap water or total fluid intake. The present findings are considered together with prevailing notions of nicotine receptor alterations and possible cross-sensitization effects modulating substance abuse.

Effects of clonidine and alpha-adrenoceptor antagonists on motor activity in DSP4-treated mice I: dose-, time- and parameter-dependency

In three experiments the acute effects of clonidine administration upon locomotor and rearing behaviour of mice pretreated with the selective noradrenaline (NA) neurotoxin, DSP4 (1 x 75 mg/kg, i.p.) 10-12 days previously, were studied. Clonidine (0.01, 0.05, 0.25, 1.25 and 3.0 mg/kg, i.p.) induced a dose-dependent reduction of motor activity during the initial 30 min of testing in both DSP4-treated and control mice; this effect was attenuated by DSP4 treatment in the 0.01, 0.05, 0.25 and 3.0 mg/kg dose groups. By the third 30-min period of testing (60-90 min), each clonidine dose group, except the highest (3.0 mg/kg) dose for locomotion and the two highest (1.25 and 3.0 mg/kg) doses for rearing, induced increases in motor activity in the control mice. In DSP4-treated mice, a large increase in locomotor counts was produced by the 0.05 mg/kg dose of clonidine with lesser increases induced by the 0.01 mg/kg dose group, whereas a lesser effect of the 0.05 mg/kg group (30-60 min) was obtained for rearing but a larger effect of the 0.25 mg/kg group (60-90 min). Yohimbine (0.5 mg/kg, i.p., 15 min before clonidine) attenuated the suppressive effects of clonidine (0.01 and 0.05 mg/kg) during the initial 30 min of testing and markedly increased locomotor and rearing counts, both by itself and in combination with each dose of clonidine, in both DSP4-treated and control mice over the following 90 min of testing. Yohimbine treatment attenuated the large increase in locomotor counts induced by the 0.05 mg/kg dose of clonidine in the NA-denervated mice. Dihydroergotamine (0.5 mg/kg, i.p., 15 min before clonidine) did not antagonise either the initial suppressive effect or the later supersensitivity effect of the 0.05 mg/kg dose of clonidine. DSP4 treatment by itself reduced motor activity. The effects of clonidine, dose- and time-dependently, by itself or in co-administration with alpha-adrenoceptor antagonists, in DSP4-treated or control mice displayed denervation-induced supersensitivity that appear to reflect mainly postsynaptic alpha2-adrenoceptor mediation.

Effects of clonidine and alpha-adrenoceptor antagonists on motor activity in DSP4-treated mice II: interactions with apomorphine

Adult mice were administered either the noradrenaline (NA) neurotoxin, N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4) or distilled water (control), 10-12 days before motor activity testing, and 6 h before testing all the mice were administered reserpine (10 mg/kg), the monoamine-depleting agent. The interactive effects of (I) clonidine, the alpha(2)-adrenoceptor agonist, with the dopamine (DA) agonist, apomorphine, and the alpha(2)-antagonist, yohimbine, and (II) with either yohimbine or the alpha(1)-antagonist, prazosin, upon motor behaviour in activity test chambers were studied in reserpinized DSP4-treated and control mice. It was shown that apomorphine (3 mg/kg) increased locomotor and total activity in both reserpinized DSP4-treated and control mice but the effect was attenuated in the DSP4 mice. Co-administration of clonidine (3 mg/kg) with apomorphine potentiated the effects of apomorphine on motor activity and this effect was enhanced markedly by DSP4 pretreatment. Yohimbine (10 mg/kg) antagonized the motor activity-stimulating effects of apomorphine in both DSP4-treated and control mice. Co-administration of clonidine with apomorphine, following yohimbine, restored motor activity levels to those obtained in the absence of yohimbine and this effect upon locomotor activity was enhanced by DSP4 pretreatment. The effects of clonidine on motor activity were enhanced by NA-denervation. Prazzosin (3 mg/kg) enhanced the locomotor activity of both reserpinized DSP4-treated and control mice after the initial 30-min period but was not affected by DSP4 treatment. Analysis of post-decapitation convulsions (PDCs) indicated loss of the reflex by DSP4 pretreatment. Reserpine pretreatment abolished the initial, exploratory phase (30 min) of motor activity. These results demonstrate interactions between NA and DA systems that may bear eventual relevance to neurologic disorders such as parkinsonism.

MPTP-induced deficits in motor activity: neuroprotective effects of the spintrapping agent, alpha-phenyl-tert-butyl-nitrone (PBN)

In Experiment 1, groups of mice were administered either saline or MPTP (2 x 30 mg/kg, s.c., separated by a 24-hr interval) 30 min after being injected either PBN (15, 50 or 150 mg/kg, s.c., low, medium and high doses, respectively) or L-Deprenyl (0.25 or 10.0 mg/kg, s.c., low and high doses, respectively), the reference compound used, or saline. Tests of spontaneous motor activity 14 days later indicated that the MPTP-induced hypokinesia for locomotion and rearing was alleviated by prior administration with PBN (50 or 150 mg/kg) or L-Deprenyl (10.0 mg/kg); lower doses of PBN (15 mg/kg) and L-Deprenyl (0.25 mg/kg) did not affect the MPTP-induced deficits. Dopamine (DA) concentrations in the striatum confirmed a more severe loss of DA in the MPTP, PBN (15) + MPTP and Deprenyl(0.25) + MPTP groups than in the control group. Significant protection of DA was observed in the PBN(50) + MPTP, PBN(150) + MPTP and Deprenyl(10) + MPTP groups that did not exhibit an hypokinetic behaviour. In Experiment 2, the effects of repeated treatment with PBN (50 mg/kg, s.c. over 12 days), post-MPTP, were studied in aged (15-month-old) and young (3-month-old) mice. Subchronic administration of PBN increased substantially the motor activity of old and young mice that had received MPTP. Aged control (saline) mice showed an activity deficit compared to young control mice; this deficit was abolished by repeated PBN treatment. The results suggest that moderate-to-high doses of PBN whether injected in a single dose prior to MPTP or subchronically following MPTP injections may afford protective effects against both the functional changes and DA-loss caused by MPTP treatment, possibly through an antioxidant mechanism.

Health of women: associations among life events, social support, and personality for selected patient groups

This study examined the effects of life events, social support, personality traits, and siblings' birth-order on the health of women. 199 middle-class participants were included. 95 women, randomly assigned from four different patient groups, were compared with a control group of 96 randomly selected women without any special health problems. They completed a questionnaire which included questions regarding family background, health, different life events, social support, and signs of disease and a projective test, the Sivik Psychosomatism Test. Analysis indicated that report of negative life events was associated with more physical symptoms than positive life events and that the patient groups reported more negative life events and less social support than the control group.

Maze learning and motor activity deficits in adult mice induced by iron exposure during a critical postnatal period

Newborn mice were administered Fe(2+) (iron succinate: 7.5 mg/kg, b. wt) on either Days 3-5, 10-12 or 19-21, or vehicle (saline) at the same times, postnatally. Spontaneous motor behaviour and radial arm maze learning were tested at the age of 3 months. It was found that mice treated with Fe(2+) during postnatal Days 10-12 were markedly hypokinetic during the 1st 20-min test period and hyperkinetic during the 3rd and final 20-min test period. These mice showed an almost complete lack of habituation of spontaneous motor activity parameters to the test chambers. In the radial arm maze, the Days 10-12 treatment group evidenced significantly both more errors in arm choices and longer latencies to acquire all eight pellets; these mice showed also a severe trial-to-trial retention deficit as indexed by retention quotients. These behavioural deficits were observed also in animals treated with Fe(2+) during postnatal Days 3-5, but the effects were less pronounced, indicating the higher susceptibility of the brain for Fe(2+)-induced damage during Days 10-12 postpartum. Treatment with Fe(2+) on Days 19-21 did not induce behavioural alterations in comparison with its respective control (vehicle) group. Analysis of total brain iron content indicated significantly more iron (microg/g) accumulation in the basal ganglia, but not frontal cortex, of mice from the Days 3-5 and 10-12 Fe(2+) (7.5 mg/kg) treatment groups. The contribution of iron overload during the immediate postnatal to later functional deficits seems to implicate symptoms of Parkinsonism but the kinetics of iron uptake to the brain and its regional distribution at this critical period of development awaits elucidation.

Restoration and putative protection in Parkinsonism

Synergistic antiparkinsonian actions of different classes of putative therapeutic agents co-administered with a subthreshold dose of L-3,4-dihydroxyphenylalanine (L-Dopa) (5 mg/kg) in drug-naive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice as well as the restorative actions of those compounds in suprathreshold L-Dopa-tolerant MPTP-treated mice subjected to "wearing-off" of L-Dopa efficacy were assessed in a series of experiments. The classes of compounds studied included the noncompetitive NMDA antagonists, memantine, amantadine and MK-801, the anticonvulsive and putative anticonvulsive agents, lamotrigine, FCE 26743, phenytoin, the monoamine oxidase inhibitors, L-Deprenyl, amiflamine, alpha-ethyltryptamine, clorgyline and guanfacine. In this final case, the restorative effects of clonidine and guanfacine were antagonized by the alpha(2)-adrenoceptor antagonist, yohimbine, but not the alpha(1)-adrenoceptor antagonist, prazosin. Within each class of potentially therapeutic agents a differential restorative efficacy was obtained, but the combination of different doses of apomorphine with clonidine failed to restore motor activity. Finally, the neuroprotective actions of acute and subchronic administration of the nitrone spin-trapping compound, alpha-phenyl-tert-butyl nitrone upon the spontaneous motor behaviour and striatal dopamine concentrations of MPTP-treated mice was examined.

Neuroprotective and neurorestorative strategies for neuronal injury

Mechanisms of neuronal cell death in apoptosis and necrosis are examined. Neurotoxic processes underlying cellular destruction may involve N-methyl-D-aspartate (NMDA) receptor activation and/or activation of neuronal nitric oxide synthase but the depletion of energy and generation of free radicals appears to be critical. In Alzheimer's disease the damaging effects of peroxynitrite and exposure to beta-amyloid peptide is evident. Mitochondrial dysfunction is involved in several neurodegenerative diseases including Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease as well as Alzheimer's disease and in these disorders the innovations offered by techniques ranging from transgenic mouse models of the disorder to cell culture preparations are remarkable. Agents of neuroprotection and neurorestoration possess either characteristics specific to particular disorders or have a general applicability or both. The vast array of agents available are for the most part the objectives of laboratory examinations but an increasing selection of compounds are reaching the clinical necessities thereby influencing current strategic notions to modify tactical contingencies. Among the agents listed are included: inhibitors of the enzyme poly-ADP-ribose polymerase, inhibition of apoptotic cell death, agents acting on mitochondrial permeability transition, excitatory amino acid antagonists, applications of neurotrophins, immunophilins, agents influencing heme oxygenase-1 expression and iron sequestration in aging astroglia, improvements in mitochondrial energy production or buffering, and finally dopaminemimetics with differential affinities for dopamine receptors.

Effects of co-administration of anticonvulsant and putative anticonvulsive agents and sub/suprathreshold doses of L-dopa upon motor behaviour of MPTP-treated mice

The effects of co-administration of the dopamine precursor, L-Dopa, with anticonvulsant and putative anticonvulsive agents upon the motor activity of hypoactive MPTP-treated C57 BL/6 mice were measured in six experiments. In each case, MPTP (2 x 40 mg/kg, s.c., separated by a 24-hr interval) was administered four to six weeks prior to behavioural testing. Thus, the effects of these agents combined with either a single acute, subthreshold dose (5 mg/kg, s.c.) of L-Dopa, or, with chronically-administered, suprathreshold doses (20 mg/kg, s.c.) of L-Dopa were studied. In the former, lamotrigine, FCE 26743 and L-Deprenyl, injected 60 min before subthreshold L-Dopa (5 mg/kg), each induced an antiparkinsonian action in MPTP-treated mice that consisted of dose-specific, as opposed to dose-related, elevations of locomotion and rearing behaviour. In the latter, lamotrigine (all three measures of activity at 3 mg/kg), FCE 26743 (locomotion and total activity at 3; rearing at 1 and 3 mg/kg) and L-Deprenyl (locomotion and total activity at 1 and 3mg/kg), but not phenytoin (neither at 1 nor 3 mg/kg), reinstated the motor activity-stimulating effects of the threshold dose of L-Dopa (20 mg/kg) in L-Dopa-tolerant, MPTP-treated mice. Neurochemical analyses confirmed severe DA depletions in MPTP-treated mice. Since neither lamotrigine, FCE 26743 nor L-Deprenyl, nor subthreshold L-Dopa, by themselves increased the motor behaviour of MPTP-treated mice, a synergistic effect of the co-administration is concluded. Further, since the suprathreshold dose of L-Dopa by itself failed to stimulate motor activity in the MPTP mice following chronic (25 daily injections) administrations of the compound, it is suggested that a restorative effect, in combination with lamotrigine, FCE 26743 or L-Deprenyl was evidenced. The potential therapeutic benefits of anticonvulsant or putative anticonvulsive compounds for parkinsonian symptoms are discussed.

Neonatal iron exposure induces neurobehavioural dysfunctions in adult mice

Excess iron in the brain has been implicated in the pathogenesis of several human neurodegenerative disorders, i.e., Parkinson's and Alzheimer's disease. The neonatal period is critical for the establishment of normal iron content in the adult brain. In the present study, the long-term neurobehavioral effects of iron exposure during this period were assessed by treating NMRI mice orally with 0.0, 3.7, or 37.0 mg Fe(2+)/kg body wt on postnatal days 10-12. Spontaneous motor behavior and radial arm maze learning were tested at the age of 3 months. It was found that the mice treated with the higher dose of Fe(2+), 37.0 mg/kg body wt, were hypoactive during the first 20 min of testing but hyperactive during the final 20 min, showing an almost complete lack of habituation of spontaneous activity in the test chambers. These changes were also seen in animals treated with the lower dose of Fe(2+), 3.7 mg/kg body wt, but the effects were less pronounced, indicating a dose-response relationship. In the radial arm maze, the Fe(2+) 37.0 mg/kg group evidenced significantly both more errors in arm choices and longer latencies to acquire all eight pellets. Both dose groups showed attenuated performance increments on successive trials. Analysis of brain iron content indicated significantly more total iron (microgram/g) in the basal ganglia, but not frontal cortex, of the higher, 37 mg/kg, dose group. The knowledge of the long-term effects of iron entering the brain during this critical period of rapid brain growth is limited. Increased amounts of iron in the brain, especially in the basal ganglia, may contribute to neurodegenerative processes.

Tolerance to a suprathreshold dose of L-Dopa in MPTP mice: effects of glutamate antagonists

Three experiments were performed to study the development and manipulation of tolerance to a suprathreshold dose of L-Dopa (20 mg/kg, s.c.) in MPTP-treated and control (saline-injected) C57 Bl/6 mice. The motor activity reinstatement effect of this dose of L-Dopa upon MPTP-treated mouse behaviour deteriorated from the 13th injection (Test Day 8) of L-Dopa onwards and reached basal level (i.e. no stimulatory effects of the drug) by the 16th administration (Test Day 10). Administration of L-Dopa to control mice reduced locomotor and rearing activity throughout the tolerance development period (Test Days 1-12) during the first hour after injection, and then increased locomotor activity during the second hour. The effects of combining either a noncompetitive, MK-801, or a competitive, CGP 40116, glutamate antagonist with L-Dopa, following tolerance development, were assessed in MPTP mice on the 23rd day of L-Dopa administration (Test Day 13). MK-801 (0.1 mg/kg, s.c.) reinstated the locomotory and rearing behaviour induced by L-Dopa; CGP 40116 did so also to a greater extent in the dose range 0.01 to 0.03 mg/kg. These results indicate that MPTP-treated mice continue to offer a useful parkinsonian model also for the examination of different aspects of the "wearing-off" phenomenon of L-Dopa tolerance and in particular the putative glutamatergic involvement. The clinical consequences may be far-reaching for the utility of L-Dopa in Parkinson's disease, whether the effects demonstrated be of a reinstatement or synergistic nature, once therapeutically adequate glutamate antagonists are more readily available.

Effects of alcohol and frustration on experimental graffiti

This study aimed to examine effects between alcohol and frustration in regard to graffiti. Forty-two subjects, 21 men and 21 women were randomly assigned in equal numbers to each of the three experimental groups, namely a Control group, an Alcohol group, and an Alcohol + Frustration group (alcohol dose: 1 ml 100% alcohol/kg body weight). For the purposes of this experiment, a test (AET) was constructed that provided scores of "scrawling-graffiti" (i.e., the amount of scrawling on pictures), "destruction", "aggression", and "sexuality". An elaboration test and a test measuring the "dispositional optimism" were also applied. The primary results indicated that (a) the Alcohol + Frustration group scored significantly higher on scrawling-graffiti compared to the Control group, (b) female subjects performed graffiti-scrawling to a greater extent than male subjects in all three groups, (c) women scored significantly higher on elaboration as compared to men. These results were interpreted as supporting the hypothesis that alcohol intake by itself is unlikely to induce destructive behavior unless accompanied by a "provocative" factor (e.g. frustration) that precipitates the putative expressions of aggressiveness.

Functional changes induced by neonatal cerebral 6-hydroxydopamine treatment: effects of dose levels on behavioral parameters

Male Sprague-Dawley rats were treated neonatally with either of three different doses of 6-hydroxydopamine (6-OHDA): 50 micrograms i.c., 75 micrograms i.c., or 2 x 100 micrograms i.c.v., 30 min after a subcutaneous injection of desipramine (DMI, 25 mg/kg), in order to obtain selective lesions of mesencephalic dopamine (DA) neurons to different extents. From juvenile ages onwards, rats in each dose condition were tested for spontaneous motor activity and exploration in an openfield/holeboard setting measuring ambulation, rearing and head-dips. Between 77 and 78 days, the animals were tested in a modified, enclosed radial arm maze, followed 1 week later by tests in the circular swim maze. Finally, motor activity was tested in automated activity test chambers. In the openfield/holeboard setting, hyperactivity was seen for both rearing and ambulation in rats administered 50 micrograms 6-OHDA, whereas the 75 micrograms and 2 x 100 micrograms groups showed hyperactivity for ambulation, but hypoactivity for rearing and head-dips. All three dose groups demonstrated a retardation of learning in the radial arm maze. The 75 and 2 x 100 micrograms groups, but not the 50 micrograms group, showed impairments of acquisition in the swim maze. In the activity test chambers locomotion and rearing behavior varied as a function of 6-OHDA dose, being negatively and positively, respectively, related to DA concentration in striatum. These results show that the extent of the neonatal DA lesion determines both changes in motor- and exploratory activity as well as the occurrence and severity of acquisition impairment in spatial learning tasks.

Effects of prenatal alcohol exposure on activity and learning in Sprague-Dawley rats

Nulliparous pregnant Sprague-Dawley rats were exposed to ethanol via a liquid diet technique (FAE, fetal alcohol exposure) or administered a fixed amount of control diet from gestational day 11 to day 21. The offspring, at 2-3 months of age, were studied in tests of mechanically monitored motor activity and learning acquisition in an automatized testing cage requiring an instrumental discriminative response, where the ability to learn and relearn correlations of a light signal to water presentation was monitored. A significantly reduced activity (i.e. ramp mounting behaviour) in a novel situation was obtained in the FAE group compared to controls. The initial disruption of ramp mounting behaviour could reflect alterations in either habituation to a novel test situation, altered neophobia, or some retardation in associating these responses with the outcome of water-availability. Adult FAE rats (six months of age) showed a tendency towards a lowered acquisition performance (p = 0.06) when tested in a circular Morris-type swim maze, but no detectable differences were shown in a motor activity test chamber situation.

Alpha-phenyl-tert-butyl-nitrone (PBN) reverses age-related maze learning performance and motor activity deficits in C57 BL/6 mice

Two experiments were performed to study the effects of age and repeated administration of alpha-phenyl-tert-butyl-nitrone (PBN), the free radical spin-trapping agent, upon spontaneous motor activity levels and radial arm maze performance in normal young (3 month old) and normal aged (15 month old) C57 BI/6 mice. In Experiment 1, the aged mice were found to show reduced locomotor and rearing behaviour in comparison with the young mice. In the radial eight-arm maze learning task, the aged mice performed at a comparable level to the young mice during the first learning trial (Day 1) but made significantly more errors and showed longer total latencies during the second trial presented 24h later. In Experiment 2, the aged and young mice were subchronically administered either PBN at a dose of 50mg/kg, s.c. over 12 days, or saline. Spontaneous motor activity was tested 72h after the last injection. 36h later the first test trial in the radial arm maze was presented; this was followed after a further 24h by the second test trial. Subchronic treatment with PBN increased locomotion counts in the aged (15 month old) mice during the 60min test period, but decreased rearing during the first 30min of the test period. In the radial arm maze, the performance deficit shown during the second test trial by the aged mice was abolished by repeated PBN administration; both the number of errors and the latencies to all eight pellets were significantly reduced in the aged mice that received PBN. PBN did not exert any effects upon the performance of the young mice. These results, considered in conjunction with other studies using gerbils or rats, implicate the involvement of free radical species in the deterioration of function in the aged C57 BI/6 mouse.

Prenatal coexposure to metallic mercury vapour and methylmercury produce interactive behavioural changes in adult rats

Pregnant rats were 1) administered methyl mercury (MeHg) by gavage, 2 mg/kg/day during days 6-9 of gestation, 2) exposed by inhalation to metallic mercury (Hg degrees) vapour (1.8 mg/m3 air for 1.5 h per day) during gestation days 14-19, 3) exposed to both MeHg by gavage and Hg degrees vapour by inhalation (MeHg + Hg degrees), or 4) were given combined vehicle administration for each of the two treatments (control). The inhalation regimen corresponded to an approximate dose of 0.1 mg Hg degrees/kg/day. Clinical observations and developmental markers up to weaning showed no differences between any of the groups. Testing of behavioural function was performed between 4 and 5 months of age and included spontaneous motor activity, spatial learning in a circular bath, and instrumental maze learning for food reward. Offspring of dams exposed to Hg degrees showed hyperactivity in the motor activity test chambers over all three parameters: locomotion, rearing and total activity; this effect was potentiated in the animals of the MeHg + Hg degrees group. In the swim maze test, the MeHg + Hg degrees and Hg degrees groups evidenced longer latencies to reach a submerged platform, which they had learned to mount the day before, compared to either the control or MeHg groups. In the modified, enclosed radial arm maze, both the MeHg + Hg degrees and Hg degrees groups showed more ambulations and rearings in the activity test prior to the learning test. During the learning trial, the same groups (i.e., MeHg + Hg degrees and Hg degrees) showed longer latencies and made more errors in acquiring all eight pellets. Generally, the results indicate that prenatal exposure to Hg degrees causes alterations to both spontaneous and learned behaviours, suggesting some deficit in adaptive functions. Coexposure to MeHg, which by itself did not alter these functions at the dose given in this study, served to significantly aggravate the changes.

Synergistic interactions between COMT-/MAO-inhibitors and L-Dopa in MPTP-treated mice

Four experiments were performed to investigate the anti-akinesia effects of combining a sub-threshold dose (5 mg/kg, s.c.) of L-Dopa with different doses and combinations of COMT and MAO inhibitors upon the hypokinesia observed in MPTP-treated mice. Ro 40-7592 (1 and 3 mg/kg, s.c.), a novel COMT inhibitor, 60 min before L-Dopa reinstated both locomotion and rearing during a 2-hr interval after L-Dopa in MPTP mice; control mice were unaffected. The combination of Ro 40-7592 (3 mg/kg, s.c.) and pargyline (5 mg/kg, s.c.), a MAO inhibitor, with L-Dopa produced increases in both the peak effect and duration of action indicating a distinct potentiation of the effects of Ro 40-7592 by pargyline. L-Deprenyl, a MAOB inhibitor, together with L-Dopa, restored locomotion and rearing behaviour at all three doses applied (1, 3 and 10 mg/kg, s.c.); in control mice, motor activity was stimulated at the higher doses (3 and 10 mg/kg, s.c.), independent of L-Dopa administration. Combining L-Deprenyl (3 mg/kg, s.c.) with Ro 40-7592 (3 mg/kg, s.c.) one hr before L-Dopa to MPTP mice potentiated the restorative effects of each compound by itself, although no increase in peak effect was obtained. In the control mice, L-Deprenyl plus Ro 40-7592 or L-Deprenyl, by itself, stimulated motor activity following injection of L-Dopa. Marked dopamine (DA) depletions in the striatum of MPTP-treated mice were evident. The present results demonstrate that the effects of the COMT/MAO inhibitors in combination, and in conjunction with L-Dopa (at a dose that was without effect by itself), were well in excess of a summation of their individual effects. It was concluded therefore that a synergism of the restorative, anti-akinesic action of these compounds in MPTP-treated mice could offer a broader therapeutic spectrum in the treatment of Parkinson's disorder.

Effect of the competitive NMDA antagonist, CGP 40 116, and a low dose of l-Dopa on the motor activity deficit of MPTP-treated mice

Three experiments were performed to investigate the effects of combining the active D-stereoisomer of CGP 37 849, i.e. the glutamatergic antagonist, CGP 40 116, with l-dopa, in mice that had undergone treatment with the neurotoxin, MPTP. In the first experiment, the decreased motor activity in MPTP-treated mice was alleviated by the administration of a low dose of l-dopa (5mg/kg, s.c.) together with a low dose of CGP 40 116 (30µg/kg). This dose was inactive in the control (saline-treated) mice. The highest dose of CGP 40 116 used (3000µg/kg) stimulated activity in the control mice. In Experiment 2, the inactive L-stereoisomer, i.e., CGP 40 117, was found to be inactive at doses (3 and 30µg/kg) effective with CGP 40 116. The effects of CGP 40 116 and l-dopa on the 24-h activity of mice tested under either day-night or night-day conditions, were more marked and longer lasting in the night-day condition. Taken together, the results from all three experiments show that CGP 40 116 in a dose range of 1-30µg/kg in combination with l-dopa (5mg/kg, s.c.) alleviated the reduced motor activity in MPTP-treated mice whereas higher doses of CGP 40 116 (100, 300, or 3000µg/kg) or lower doses (0.1 and 0.3µg/kg) were without effect. These experiments are interpreted as support for current views on glutamatergic-dopaminergic interactions in Parkinsonism and offer further evidence for the MPTP mouse model of the disease.

Synergistic interactions between NMDA-antagonists and L-dopa on activity in MPTP-treated mice

Four experiments were performed to investigate whether or not coadministration of NMDA-antagonists potentiate the effect of an ineffective dose of L-Dopa on motor activity in hypoactive MPTP-treated mice. Motor activity was measured in an automated system recording both locomotion (horizontal) and rearing (vertical) activity. L-Dopa alone, at doses of 10 and 20 mg/kg, but not 5 mg/kg, expressed an anti-akinesia effect in MPTP-treated mice. The non-competitive NMDA-antagonist MK-801 (0.03, 0.1, and 0.3 mg/kg) increased by itself both locomotion (0.1 and 0.3 mg/kg) and rearing (0.03 mg/kg) in control (saline-treated) mice whereas no effect was seen in the MPTP-treated mice. Combined with 5 mg/kg L-Dopa, MK-801 (0.1 mg/kg) increased locomotion in MPTP-treated mice. There was no interaction seen between L-Dopa and MK 801 in the control mice. CGP40116 and CGP40117, the active D- and the inactive L-stereoisomer of the competitive NMDA-inhibitor CGP37849, respectively, were also administered together with 5 mg/kg L-Dopa. Both doses (0.003 and 0.03 mg/kg) of CGP40116 in contrast to CGP40117, produced anti-akinesia effect in MPTP-treated mice. CGP40116 (0.0001 to 0.1 mg/kg) together with 5 mg/kg L-Dopa did not affect behaviour in control mice but produced (0.01 mg/kg CGP40116 and 5 mg/kg L-Dopa) in the MPTP-treated mice an anti-akinesia effect. Our findings indicate that the non-competitive NMDA-antagonist MK-801, at doses with reported side-effects, only increase locomotion while rearing remained unaltered in MPTP-treated mice when combined with 5 mg/kg L-Dopa. Only the active stereoisomer CGP40116 in contrast to CG40117, at doses far below reported side-effects, dose-dependently modulated the anti-akinesia effect of a subthreshold dose of L-Dopa. Such data thus support the notion that this behavioural modulation was regulated via NMDA-receptors. The synergism between L-Dopa and the competitive NMDA-antagonist CGP40116 has a potential in treatment of Parkinson's disease to reduce the side-effects of doses of L-Dopa that are used today.

Effects of D1 and D2 agonists on spontaneous motor activity in MPTP treated mice

Two experiment were performed to study the effect of combining bromocriptine with SKF 38393 (SKF), or vice/versa, upon parameters of spontaneous motor activity in MPTP treated and saline (control) treated mice. Treatment with MPTP (2 x 40 mg/kg, subcutaneously) induced a hypoactive condition compared with saline treated mice. Bromocriptine (10 mg/kg, subcutaneously), administered to MPTP mice 2 hr, but not 1 or 4 hr, after SKF (6 mg/kg, subcutaneously) caused a marked increase in locomotion and rearing behaviour. The administration of bromocriptine (10 mg/kg, subcutaneously) 4 hr before SKF (6 mg/kg, subcutaneously) elevated all three parameters of spontaneous activity in the MPTP treated mice, independent of the injection of SKF. Bromocriptine injection 1 or 2 hr before SKF decreased locomotion in both MPTP and control mice. Neurochemical analysis confirmed the dopamine depletion in the MPTP treated mice. These results are discussed in terms of the reliability of the MPTP model of parkinsonism in mice and the dopamine D1/D2 receptor hypersensitivity following denervation with the neurotoxin.

MPTP-induced behavioural and biochemical deficits: a parametric analysis

Two experiments were performed to study the parametric effects of long-term administration of the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), as a functional model of parkinsonism in mice. The behavioural deficits induced by different doses of MPTP (5, 10, 20, 30 or 40 mg/kg, s.c., each injected on two occasions) at a 3-week or a 3-month treatment-testing interval were evidenced by significant reductions of spontaneous motor activity, from the 10 mg/kg dosages upwards at the 3-week interval and from 30-40 mg/kg at the 3-month interval. Significant dopamine (DA) reductions in the mouse striatum were obtained at these dose levels and intervals. The behavioural deficit of the 40 mg/kg dose (injected on two occasions) and tested at the 3-, 6-, 12-, 24- and 40-week intervals (separate as well as repeated testing groups) indicated marked and relatively comparable reductions of all three parameters of motor activity, locomotion, rearing and total activity. DA depletions were severe at all five test intervals. These results offer functional and neurochemical evidence that MPTP treatment produces permanent damage to the nigrostriatal motor system in mice.

Effects of typical and atypical antipsychotic drugs on two-way active avoidance. Relationship to DA receptor blocking profile

The dose-dependent and time-dependent effects of the novel antipsychotic compound remoxipride, as well as the reference compounds chlorpromazine, clozapine, haloperidol, pimozide and sulpiride upon the retention of two-way active avoidance (conditioned avoidance responses, CARs) were studied in male rats. The dose-dependent effects of remoxipride as well as haloperidol and chlorpromazine on the acquisition of CARs were also studied. The acquisition and retention of CARs were tested in shuttleboxes using a 1.0-mA shock intensity and a 10-stone signal (1000 Hz). All the compounds studied, including remoxipride, caused a dose-dependent impairment of acquisition and retention of CARs. The effect of remoxipride on CAR acquisition correlated with remoxipride's effectiveness to block the hyperactivity induced by the dopamine (DA) agonist apomorphine. Unlike chlorpromazine and haloperidol, the potency of remoxipride and clozapine for antagonising CAR retention was found at dose levels much lower than those producing cataleptic effects or blocking apomorphine-induced stereotypies. Based on the DA receptor blocking profile and the relative effectiveness to block CAR it is concluded that the mechanism(s) by which clozapine and remoxipride affect CAR differ from typical neuroleptic drugs. This difference may reflect an action upon different subtypes of functionally coupled DA D2 receptors.