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PubMed1984

Genotype-dependent behavioral sensitivity to mu vs. kappa opiate agonists. I. Acute and chronic effects on mouse locomotor activity.

The locomotor activity (LMA) effects of morphine (MRP) and (+/-)-ethylketocyclazocine (EKC) were studied in two inbred mouse strains, C57B1/6J (C57) and DBA/2J (DBA). MRP (3.2-100 mg/kg) caused a monophasic stimulation, a "running fit," in naive C57 mice and a biphasic, depression-stimulation in DBA mice. In contrast, EKC (3.2-100 mg/kg) elicited a biphasic, catalepsy-stereotypy in both strains. The later stereotypic actions of acute EKC, although including sporadic running, were clearly unlike the persistent circling of MRP-stimulation. The LMA responses to MRP and EKC were stereoselective and antagonized by naloxone. Tolerance to the initial depression of activity by MRP in DBA mice developed after chronic administration of either MRP or EKC (32 mg/kg s.c., b.i.d. for 1 week); the intensity of MRP-stimulation, however, increased in both strains. This sensitization to MRP was not overcome with a chronic treatment schedule of 100 mg/kg t.i.d. for 10 days of MRP or EKC. Mice treated chronically with EKC were completely tolerant to its cataleptic and stereotypic effects. Moreover, in these mice EKC elicited a vigorous, MRP-like running fit. Prolonged MRP administration, on the other hand, conferred no tolerance whatsoever to the cataleptic effect of EKC. Taken together with the genetic differences in the acute actions of MRP, this lack of cross-tolerance indicates that distinct neural mechanisms mediate the acute LMA responses to the two narcotics in these mice.

Animals↗
PubMed1994

Tolerance to oral and IP caffeine: locomotor activity and pharmacokinetics.

Locomotor activity increase was a bitonic function of acute caffeine IP doses (2.5-40 mg/kg) in rats. When the schedule-induced polydipsic, orally self-administered dose of caffeine was increased over blocks of daily 3 h sessions from 9.3 to 36.5 mg/kg, postsession activity increased monotonically as a function of dose. The rate of tolerance development to the increase in locomotor activity produced by caffeine depended on the route of administration. Tolerance onset occurred on the fourth day of chronic IP doses, but remained incomplete after 21 doses. With the highest dose level of oral caffeine self-administration, tolerance developed on day 13, but remained incomplete even after 17 doses. Acute tolerance occurred for each of the IP doses, whereas a linear relation between locomotor activity and serum caffeine concentration was obtained after oral self-administration. There were two- to threefold higher locomotor activity AUCs(4 h) with oral caffeine at three dose levels compared to the activity AUCs(4 h) for IP doses.

Administration, Oral↗
PubMed2001

Neuroactive steroids modulate crustacean locomotor activity.

We examined the effects of neuroactive steroids known to modulate gamma-aminobutyric acid(A) (GABA)(A) receptor activity, on locomotor activity in a submerged circular open-field apparatus. Juvenile male lobsters, Homarus americanus, were treated with a single administration of an agonist, 3alpha-hydroxy-5alpha-pregnan-20-one (allopregnanolone, 3alpha,5alpha-TH PROG), an antagonist, pregnenolone sulfate (PREGS), or vehicle alone. 3alpha,5alpha-TH PROG treatment (125 and 250 microg) significantly reduced while PREGS significantly elevated locomotor activity in a dose-dependent manner similar to diazepam. PREGS increased locomotor activity at 30 and 60 microg, while diminishing such activity and altering locomotor patterns at 120 microg. These results suggest that neuroactive steroids may affect crustacean GABA receptors in a fashion similar to the GABA(A) type found in the vertebrates, and that they may be involved in the regulation of locomotor behavior.

Animals↗
PubMed1988

The effect of chronic lithium administration and withdrawal on locomotor activity and apomorphine-induced locomotor stimulation in rats.

The effect of chronic lithium administration and withdrawal on locomotor activity and apomorphine-induced locomotor stimulation in rats was studied. Chronic lithium administration caused a decrease in locomotor activity, which might be due to a lithium-induced decrease of exploratory behaviour. Chronic lithium administration had no effect on apomorphine-induced locomotor stimulation. However, apomorphine-induced locomotor stimulation was increased two days after the withdrawal of lithium while no difference was found after four days, suggesting a transient increase in postsynaptic dopamine (DA) receptor sensitivity following lithium withdrawal.

Animals↗
PubMed1990

Effects of morphine, ethylketocyclazocine, N-allylnormetazocine and naloxone on locomotor activity in the rabbit.

Locomotor activity was studied in the rabbit following injections of morphine, ethylketocyclazocine and N-allylnormetazocine. All three drugs produced only depression of activity. The opioid antagonist naloxone antagonized the effects of both morphine and ethylketocyclazocine. Naloxone (0.1 mg/kg) did not antagonize the effects of N-allylnormetazocine. Naloxone alone depressed locomotor activity at doses above 0.3 mg/kg. This effect of naloxone was partially antagonized by 0.1 mg/kg ethylketocyclazocine, but not by 0.1 mg/kg morphine. The GABA agonist muscimol (0.1 and 1.0 mg/kg) also did not antagonize the effect of naloxone on locomotor activity. Finally, amphetamine did not produce a great deal of locomotor activation in the rabbit, which may indicate that increasing activity in the rabbit by drug intervention may be inherently difficult. These results indicate that the opioids have effects in the rabbit that are clearly different from those observed in rodents, where morphine and N-allylnormetazocine have been reported to produce locomotor activation, and naloxone typically has little effect. In addition, the effects of the opioids on locomotor activity were clearly distinguishable from their effects on learning in the rabbit. While morphine and ethylketocyclazocine were approximately equipotent in depressing locomotor activity, morphine is much less potent than ethylketocyclazocine in retarding acquisition of the classically conditioned nictitating membrane response in the rabbit.

Animals↗
PubMed1993

Reversal of the influence of group Ib afferents from plantaris on activity in medial gastrocnemius muscle during locomotor activity.

1. Rhythmic locomotor activity was evoked in clonidine-treated acute and chronic spinal cats, and the effect of stimulating group I afferents from the plantaris muscle on the timing and magnitude of bursts in medial gastrocnemius (MG) motoneurons was examined. 2. The locomotor rhythm was entrained when group I afferents in the plantaris nerve were electrically stimulated with trains of stimuli presented at rates above and below the intrinsic frequency of the rhythmic activity. During entrainment at rates higher than the intrinsic frequency, a burst of activity in ipsilateral MG motoneurons was initiated approximately 40 ms after the onset of each stimulus train. At lower rates of entrainment the onset of MG bursts preceded the onset of the stimulus trains, and each stimulus train had an excitatory effect on the MG burst with a latency in the range of 30-50 ms. A similar excitatory effect was observed when the stimulus trains were triggered at a preset delay after the endogenous generation of the MG bursts. 3. The excitatory action of plantaris group I afferents on the MG motoneurons was only seen during periods of locomotor activity. In the absence of rhythmic activity, the same stimulus trains reduced any ongoing tonic activity in MG motoneurons. 4. Vibration of the plantaris muscle to preferentially activate group Ia afferents neither entrained the locomotor rhythm nor increased the magnitude of the MG bursts. 5. We conclude that during locomotor activity, input from group Ib afferents of the plantaris muscle has an excitatory action on the system of interneurons generating the extensor bursts, i.e., on the extensor half-center of the central rhythm generator.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed2001

Phrenic, intercostal and sympathetic activity related to fictive locomotor activity of limb muscles in spinal cats.

During L-DOPA induced fictive spinal locomotion co-ordinated rhythmic activities in external and internal intercostal, phrenic and sympathetic nerves were observed which were always co-ordinated with locomotor activity in forelimb and hindlimb muscle nerves. If long lasting tonic activity was induced by cutaneous nerve stimulation or asphyxia this activity was observed in limb motor nerves as well as in respiratory motor and sympathetic nerves. A slow independent activity of the phrenic and intercostal nerves or the sympathetic nerves which could be related to a normal respiratory rhythm or independent sympathetic rhythms was not observed. The findings indicate that during fictive spinal locomotion the activity of spinal rhythm generators for locomotion irradiates onto respiratory and sympathetic spinal neurones.

Animals↗
PubMed1981

Differential effects of l-amphetamine on ontogeny of active avoidance, intertrial responses, and locomotor activity.

Two experiments examined the effects of various doses of l-amphetamine on locomotor activity, two-way avoidance, and intertrial responses in rats that were 15, 17, 21, 36, and 90 days of age. In the first experiment, testing began 20 min after drug administration and 100 avoidance trials were given. In the second experiment, testing began immediately after drug treatment and 200 trials were given. In the two youngest groups, shuttle crossings during adaptation were increased by the highest doses. The typical inverted U-shaped function between amphetamine dose and locomotor activity found in adults began to emerge at 36 days of age. Generally, at the two youngest ages, there was a dose-related increase in avoidance and intertrial responses on the first few blocks of trials and then a decrease across trials. In 21-day rats, the drug increased avoidance on the first few trial blocks but acquisition was altered only slightly. Acquisition of 36- and 90-day rats was increased, but this increase was greater in adults. It appears likely that development of CNS catecholaminergic neurons is responsible for the age-dependent behavioral effects of l-amphetamine.

Adaptation, Physiological↗
PubMed1988

Differential effects on active avoidance performance and locomotor activity of two major enkephalin metabolites, tyr-gly-gly and des-tyr-[leu]enkephalin.

We examined the effects of two enkephalin metabolites, des-tyr-[leu]enkephalin and tyr-gly-gly, on one-way active avoidance conditioning in mice. These metabolites are products of the two major enkephalin hydrolyzing enzymes in plasma, aminopeptidase and angiotensin converting enzyme. Like [leu]enkephalin from which it may be formed, tyr-gly-gly impaired avoidance acquisition, and its dose-response function for this effect was U-shaped. Also like [leu]enkephalin, tyr-gly-gly did not alter locomotor activity. On the other hand, des-tyr-[leu]enkephalin, at the doses tested, was without effect on avoidance conditioning but produced decreased locomotion. These data suggest that the tyrosine end of the enkephalin molecule may be important for its effects on conditioning. Because of their low opioid potencies, it is unlikely that the behavioral actions of tyr-gly-gly and des-tyr-[leu]enkephalin are mediated through opioid receptors.

Animals↗
PubMed2000

A psychopharmacological study of the relationship between brain catalase activity and ethanol-induced locomotor activity in mice.

OBJECTIVE: The present experiments analyze the effects of the brain catalase inhibitor 3-amino-1,2,4-triazole (AT) on the locomotor activity induced by ethanol. METHOD: In the first experiment, mice received injections of either AT (0.5 g/kg) or saline (S) 5 hours prior to an ethanol injection (0, 0.8, 1.6, 2.4, 3.2 or 4 g/kg). In the second experiment, five different groups of mice received injections of AT (0, 0.010, 0.030, 0.060, 0.125, 0.250 or 0.500 g/kg) 5 hours prior to being injected with 1.6 g/kg of ethanol. In the third experiment, six groups of mice were treated with AT (0.5 g/kg), simultaneously, 2.5, 5, 10 or 20 hours before the administration of 1.6 g/kg of ethanol. Immediately after ethanol injection, mice were placed individually in the open-field apparatus for 20 minutes. In another set of experiments, the effects of AT on brain catalase activity were studied. Animals were injected with AT at 0, 0.010, 0.030, 0.060, 0.125, 0.250 or 0.500 g/kg, and 5, 10 or 20 hours following AT treatment mice were perfused and the brain was removed. RESULTS: Pretreating mice with AT reduces ethanol-induced locomotor activity (1.6, 2.4 and 3.2 g/kg) without altering spontaneous locomotion. Pretreatment with AT (from 0.125 g/kg to 0.5 g/kg) produced a clear dose-dependent decrease of ethanol locomotion and brain catalase activity. The effect of AT was observed 5 and 10 hours after the injection of this drug, and it disappeared 20 hours following AT treatment. CONCLUSIONS: Current data showed a parallel property of AT in producing a remarkable dose- and time-dependent decrease in catalase activity and ethanol locomotion.

Amitrole↗
PubMed1991

Ventral pallidal microinjections of receptor-selective opioid agonists produce differential effects on circling and locomotor activity in rats.

Locomotor activity was investigated following microinjections of receptor-selective opioid agonists into the ventral pallidum (VP) of rats. In Expt. 1, male Long-Evans rats were treated with unilateral microinjections of the mu agonist [D-Ala2-MePhe4, Gly-ol5]-enkephalin (DAGO), the delta agonist [D-Pen2, D-Pen5]-enkephalin (DPDPE) or the kappa agonist U50,488H, and the rate and duration of circling behaviour were measured. DAGO (0.01, 0.1, 1.0 nmol) produced a dose-dependent increase in contralateral circling; pretreatment with 1.0 mg/kg naltrexone blocked the circling induced by the highest dose. The behavioral effect was largest when injections were targeted at the VP rather than structures dorsal to the VP. In contast to DAGO, intrapallidal DPDPE (0.01, 0.1, 1.0, 10.0 nmol) produced a slight increase in contralateral circling only at the highest dose and U50, 488H (0.01, 0.1, 1.0, 10.0 nmol) produced no effect. In Expt. 2, the effects of bilateral injections of DAGO, DPDPE and U50,488H were tested in photocell activity boxes. DAGO produced a dose-dependent increase in locomotor activity and this increase was decreased by 1.0 mg/kg naltrexone. A slight increase in activity was observed with the highest dose of DPDPE, and a slight decrease was observed with the highest dose of U50,488H. These findings confirm that opiate actions in the VP contribute to opiate-induced locomotion and suggest that mu and to some extent delta receptors are involved in this behavior.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1991

Apparent enhancement by SCH 23390 of apomorphine-induced locomotor activity in mice.

Effects of the dopamine (DA) D1 antagonist SCH 23390 and the DA D2 antagonist (-)-sulpiride on apomorphine-induced characteristic changes in spontaneous motor activity were investigated in mice using the system we have devised for automatically analyzing animal behaviors in mice. Apomorphine (3 mg/kg, SC) markedly increased parameters of spontaneous motor activity such as locomotor activity and rearing time. Apomorphine-induced increase in locomotor activity had peaks at 5-20 and 30-50 min after administration, and its trough was closely related to the marked increase in rearing time induced by this agonist. Apomorphine-induced locomotor activity accumulated over a 40-min period from 5 to 45 min after apomorphine injection, during which apomorphine-induced increase in rearing time peaked, was significantly increased by intraperitoneal administration of 0.03 and 0.1 but not 0.01 mg/kg SCH 23390. Apomorphine-induced increase in rearing time was dose-dependently depressed by this antagonist. In contrast, (-)-sulpiride (10-40 mg/kg, IP) decreased apomorphine-induced increases in rearing time and locomotor activity rather than enhancing the latter parameter. These data suggest that the apparent enhancement by SCH 23390 of apomorphine-induced locomotor activity is mediated through DA D1 receptors and does not always correlate with depression of apomorphine-induced rearing behavior in mice.

Animals↗
PubMed1983

Substance P: structural requirements for the activation of brain catecholamine synthesis and locomotor activity in rats.

Intracerebroventricularly administered Arg-Pro-Lys-Pro-Gln-Gln-Phe-Gly-Leu-Met-NH2 (substance P, SP) enhanced the accumulation of DOPA after inhibition of the aromatic L-amino acid decarboxylase in the rat brain. SP also stimulated locomotor activity in a dose-dependent manner. A total of 31 structural analogues of SP were evaluated with respect to the action on brain monoamine synthesis as well as on locomotor activity. Catecholamine synthesis: SP1-10 was inactive which indicated that the [Met11]-NH2 terminal is essential for biological activity; [Leu10], [Phe7] and [Gln6] were also essential for activity; the minimum length requirement for activity was a hexapeptide amide structure. D-Amino acids in positions 8 or 9 increased activity. [D-Pro2]p-SP and [pGlu5, Gly7]-SP5-11 were active in the dopamine-rich areas, but inactive in the noradrenaline (norepinephrine)-predominant parts of the brain. The inactive [Ile7]-SP potentiated the effect of SP. Neither SP nor its analogues, with the exception of [Lys5,D-Leu8,D-Phe9]-SP5-11, increased the synthesis of 5-hydroxytryptophan (5-HTP). Locomotor activity: SP1-10 and [D-Phe9]-SP were as active as SP; [Ile7]-SP and [Ile7, Ile8]-SP were inactive and they did not antagonize the effect of SP. The results indicate that after chemical manipulation of the SP molecule it is possible to obtain great variation in activity and to dissociate to some extent the behavioural effects from those on brain catecholamine synthesis.

Animals↗
PubMed1986

Effects of serotonergic agonists and antagonists on the locomotor activity of neonatal rats.

The locomotor activity of neonatal rats was measured after treatment with serotonin agonists or antagonists. Treatment with the serotonin agonists 5-hydroxytryptophan or quipazine resulted in the elimination of the peak in activity which normally results from increases in activity from days 10 to 15 of life followed by decreases from days 15 to 20 of life. The drug-induced decreases in activity occurred at doses that did not alter locomotor activity after day 17, when most of the peak in activity had passed. The dose of 5 mg/kg of the serotonergic antagonist methysergide eliminated the peak in activity without changing locomotor activity after the peak had passed. The antagonists methiothepin and cinanserin only produced decreases in locomotor activity which did not appear to be related to the peak in activity. The serotonergic agonist data are compatible with the hypothesis that the development of the serotonin system contributed to the inhibition of locomotor activity. The methiothepin and cinanserin data neither confirm nor dispute the hypothesis, as their effects may have been either nonserotonergic or on serotonin receptors that were different than those acted on by the agonists.

5-Hydroxytryptophan↗
PubMed1994

Effects of diabetes on spontaneous locomotor activity in mice.

Spontaneous locomotor activity in diabetic mice was significantly greater than that in non-diabetic mice. Haloperidol and SCH23390, a selective dopamine D1-receptor antagonist, significantly reduced spontaneous locomotor activity in diabetic mice, but not in non-diabetic mice. Spontaneous locomotor activity in diabetic mice was also reduced by pretreatment with naltrindole, a selective delta-opioid receptor antagonist, and 7-benzylidenenaltrexone, a selective delta1-opioid receptor antagonist. The rate of dopamine turnover in the limbic forebrain in diabetic mice was significantly higher than that in non-diabetic mice. These findings suggest that the enhanced spontaneous locomotor activity in diabetic mice may result from increased dopamine neurotransmission, which might be due to an increase in dopamine release in mesolimbic dopamine systems. The increased dopamine neurotransmission in diabetic mice may also be due to the up-regulation of delta-opioid receptor-mediated functions.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1992

Hypergravity and aging in Drosophila melanogaster. 6. Spontaneous locomotor activity.

The spontaneous locomotor activity (SLA) of Drosophila melanogaster flies kept at various gravity levels (1-5 g) was recorded in both longitudinal and cross-sectional experiments. No gravity level effect could be detected in the longitudinal one, probably because these flies were allowed (for technical reasons) to rest at 1 g for 15% of their life. By contrast, flies kept at 5 g in the cross-sectional experiment had lower SLA scores at middle and old age than both 1 and 3 g-kept flies. The results of this series of experiments on hypergravity (HG) effects on three forms of locomotor activity (climbing activity, patterns of movement and SLA) allow to conclude that aging is accelerated in HG, even if no longevity decrease could be detected in the 1-4 g range.

Aging↗