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PubMedDate not supplied

The antinociceptive effects of intrathecally administered levonantradol and desacetyllevonantradol in the rat.

Levonantradol and its desacetylated metabolite (desacetyllevonantradol) produced a dose-dependent increase in the hot plate and tail flick response latencies following intrathecal administration in a dose range from 4 to 40 micrograms. No difference in potency between the two drugs was observed, as defined by the ED50 values obtained in either test. The duration of the effect of either drug was also dose dependent ranging from 30 to 120 minutes. No effect on placing, stepping or righting reflexes or the ability of the rats to negotiate a 60 degrees inclined plane was observed at these doses. At the highest doses, however, an exaggerated myoclonic response to abrupt muscle stretch was observed. None of those effects was antagonized by naloxone (2 mg/kg) administered intraperitoneally before or after levonantradol.

Analgesics↗

PubMedDate not supplied

Potential developmental toxicity of anatoxin-a, a cyanobacterial toxin.

Some 2000 species of cyanobacteria (blue-green algae) occur globally in aquatic habitats. They are able to survive under a wide range of environmental conditions and some produce potent toxins. Toxin production is correlated with periods of rapid growth (blooms) and 25%-70% of blooms may be toxic. Anatoxin-a is an alkaloid neurotoxin that acts as a potent neuro-muscular blocking agent at the nicotinic receptor. Acute toxicity, following consumption of contaminated water, is characterized by rapid onset of paralysis, tremors, convulsions and death. Human exposures may occur from recreational water activities and dietary supplements, but are primarily through drinking water. The current studies were conducted to examine the effect of in utero exposure on postnatal viability, growth and neurodevelopment, to evaluate the potential of in vitro embryotoxicity, and to explore the synergistic relationship between anatoxin-a and the algal toxin microcystin-LR by the oral route. The results of preliminary studies on amphibian toxicity are also reported. Time-pregnant mice received 125 or 200 microg kg(-1) anatoxin-a by intraperitoneal injection on gestation days (GD) 8-12 or 13-17. Pup viability and weight were monitored over a 6-day period. Maternal toxicity (decreased motor activity) was observed at 200 microg kg(-1) in both treatment periods. There were no significant treatment-related effects on pup viability or weight on postnatal day (PND) 1 or 6. The GD 13-17 pups were evaluated on PND 6, 12 and 20 for standard markers of neurodevelopmental maturation (righting reflex, negative geotaxis and hanging grip time). No significant postnatal neurotoxicity was observed. In vitro developmental toxicity was evaluated in GD 8 mouse embryos exposed to 0.1-25 microm anatoxin-a for 26-28 h. Perturbations in mouse yolk sac vasculature were noted from the 1.0 microm concentration in the absence of significant embryonic dysmorphology. Potential algal toxin synergism was tested in mice receiving either 0, 500 or 1,000 microg kg(-1) microcystin-LR by gavage and approximately 50 min later receiving either 0, 500, 1,000 or 2,500 microg kg(-1) anatoxin-a by the same route. No deaths occurred at any dose and no definitive signs of intoxication were observed. Stages 17 and 25 toad embryos (Bufo arenarum) were exposed to 0.03-30.0 mg l(-1) of anatoxin-a for 10 days. Adverse effects included a dose-dependent transient narcosis, edema and loss of equilibrium. Most notable was the occurrence of 100% mortality at the high dose in both groups 6-13 days post-exposure. The observed delay between initial exposure and death is highly unusual for anatoxin-a.

Animals↗

PubMedDate not supplied

Sensorimotor developmental delays and lower anxiety in rats prenatally exposed to cadmium.

Pregnant rats were treated with 0.3 or 0.6 mg cadmium (CdCl2) kg(-1) injected subcutaneously on a daily basis from gestational day 7 to day 15 (organogenesis period). One control group was not injected and the other received saline. Offspring were tested for ontogeny of sensorimotor development and at 45 or 90 days of age for anxiety behavior. The study of sensorimotor development showed that gestational exposure to 0.6 mg Cd kg(-1) produced a delay in the development of the righting reflex and of the cliff aversion in the pups. No differences were observed in the development of the negative geotaxis, nor in the ages of eye and ear opening. Anxiety studies using an elevated plus maze showed a lower anxiety in all the offspring prenatally exposed to 0.6 mg Cd kg(-1) as these rats spent more time and entered the open arms more times compared with those of the other groups. The results demonstrate that exposure to low levels of Cd during organogenesis may modify some central nervous system functions.

Animals↗

PubMed1987

Differential response of NADP-linked hepatic aldehyde dehydrogenase toward taurine: implication for behavioural effects of ethanol.

The effects of taurine, its initial precursor L-cysteine, and the major metabolite taurocholic acid on two ethanol-mediated responses in rodents were studied. Administration of a single dose of taurocholic acid reduced voluntary intake of a 5% ethanol solution by the rat. In the mouse, taurine had no effect on alcohol drinking or on the central depressant action of ethanol, as measured by the duration of ET-produced loss of the righting reflex. Likewise, taurocholic acid and L-cysteine did not significantly influence the duration of ethanol-narcosis time from control mice. Also studied were the effects of acute and short-term (7 or 10 days) administration of these compounds on hepatic ethanol and acetaldehyde metabolizing enzymes. Short-term administration of an equimolar concentration of taurine enhanced endogenous NADP-linked rat liver aldehyde dehydrogenase (L-ALDH) as contrasted with inhibition of the same enzyme by L-cysteine. Short-term (7 days) treatment with L-cysteine induced rat liver NAD-linked ALDH, but acute (single dose) treatment did not. Taurocholic acid short-term administration caused an induction and an inhibition of endogenous mouse liver alcohol dehydrogenase (L-ADH) and L-ALDH, respectively. The results suggest that taurine does not directly interact with ethanol. However, its major metabolite, taurocholic acid, may cause rapid metabolic conversion of ethanol to acetaldehyde by induction of L-ADH, which is then slowly metabolized due to a concomitant inhibition of L-ALDH. This may cause a build-up of acetaldehyde and thereby produce adverse reactions similar to those resulting from the combination of disulfiram and ethanol.

Aldehyde Dehydrogenase↗

PubMed1975

Behavioral adaptation in neonatal chicks following embryonic vestibular system rearrangement.

Micro-surgery was performed on chick embryos during the second day of incubation (45-50 hours). Either one otocyst was removed or was rotated 180 degrees and reimplanted. The chicks' behavior was studied for 1-13 weeks after hatching. The unilateral loss or rearrangement of vestibular (and auditory) input led initially to abnormal behavior patterns, usually consisting of poor righting reflexes, deficits in locomotion, balance and pecking accuracy, and a pronounced head nystagmus. However, in every case, these abnormalities were corrected within a few days after hatching, so that the operated animals became almost indistinguishable from normal controls. Histological evidence confirmed the extent of the loss of the vestibular and auditory structures and nuclear amalgams. The observed capacity of the neonatal chick to adapt to this sensory loss or disorientation is a rather rare example of infraprimate behavioral adjustment or modifiability, contrasting with the frequent demonstrations of behavioral rigidity in lower forms.

Adaptation, Physiological↗

PubMed2005

Minocycline reduces lipopolysaccharide-induced neurological dysfunction and brain injury in the neonatal rat.

Preferential brain white matter injury and hypomyelination induced by intracerebral administration of the endotoxin lipopolysaccharide (LPS) in the neonatal rat brain has been characterized as associated with the activation of microglia. To examine whether inhibition of microglial activation might provide protection against LPS-induced brain injury and behavioral deficits, minocycline (45 mg/kg) was administered intraperitoneally 12 hr before and immediately after an LPS (1 mg/kg) intracerebral injection in postnatal day 5 (P5) Sprague-Dawley rats and then every 24 hr for 3 days. Brain injury and myelination were examined on postnatal day 21 and the tests for neurobehavioral toxicity were carried out from P3 to P21. LPS administration resulted in severe white matter injury, enlarged ventricles, deficits in the hippocampus, loss of oligodendrocytes and tyrosine hydroxylase neurons, damage to axons and dendrites, and impaired myelination as indicated by the decrease in myelin basic protein immunostaining in the P21 rat brain. LPS administration also significantly affected physical development (body weight) and neurobehavioral performance, such as righting reflex, wire hanging maneuver, cliff avoidance, locomotor activity, gait analysis, and responses in the elevated plus-maze and passive avoidance task. Treatment with minocycline significantly attenuated the LPS-induced brain injury and improved neurobehavioral performance. The protective effect of minocycline was associated with its ability to attenuate LPS-induced microglial activation. These results suggest that inhibition of microglial activation by minocycline may have long-term protective effects in the neonatal brain on infection-induced brain injury and associated neurologic dysfunction in the rat.

Age Factors↗

PubMed2006

Disease progression of human SOD1 (G93A) transgenic ALS model rats.

The recent development of a rat model of amyotrophic lateral sclerosis (ALS) in which the rats harbor a mutated human SOD1 (G93A) gene has greatly expanded the range of potential experiments, because the rats' large size permits biochemical analyses and therapeutic trials, such as the intrathecal injection of new drugs and stem cell transplantation. The precise nature of this disease model remains unclear. We described three disease phenotypes: the forelimb-, hindlimb-, and general-types. We also established a simple, non-invasive, and objective evaluation system using the body weight, inclined plane test, cage activity, automated motion analysis system (SCANET), and righting reflex. Moreover, we created a novel scale, the Motor score, which can be used with any phenotype and does not require special apparatuses. With these methods, we uniformly and quantitatively assessed the onset, progression, and disease duration, and clearly presented the variable clinical course of this model; disease progression after the onset was more aggressive in the forelimb-type than in the hindlimb-type. More importantly, the disease stages defined by our evaluation system correlated well with the loss of spinal motor neurons. In particular, the onset of muscle weakness coincided with the loss of approximately 50% of spinal motor neurons. This study should provide a valuable tool for future experiments to test potential ALS therapies.

Aging↗

PubMed1976

Pharmacology of Quercus infectoria.

The galls of Quercus infectoria (Fagaceae), a commonly available plant in Iran, were studied pharmacologically. Two fractions were employed, a dried acetone-treated methanol extract dissolved in water (Fraction A) and a subfraction prepared by chloroform-methanol extraction (Fraction B). Fraction A was active as an analgesic in rats and significantly reduced blood sugar levels in rabbits. Fraction B had CNS depressant activity. Data obtained with a treadmill indicated a decreased activity ratio by Fraction B, suggesting a possible interference in motor coordination. It potentiated the barbiturate sleeping time significantly without changing the onset time or the loss of the righting reflex. In addition, Fraction B exhibited a moderate antitremorine activity by causing a delay in the onset and a decrease in the severity of tremorine-induced tremors. The local anesthetic action of Fraction B was evident due to the complete blockade of the isolated frog sciatic nerve conduction.

Analgesics↗

PubMed1977

Alterations induced in distribution and in vivo metabolism of imipramine by pregnenolone-16alpha-carbonitrile.

Female rats were given pregnenolone-16alpha-carbonitrile (I) to investigate its in vivo effects on the loss of the righting reflex and the mortality rate induced by imipramine as well as the concentrations of this drug and its metabolite, desipramine, in plasma, brain, liver, lungs, and kidneys. The protective action of I was associated with diminished organ levels of imipramine (catatoxic mechanism), and the relationship between brain and plasma imipramine concentrations remained unaltered. Desipramine-imipramine molar ratios were increased, indicating an elevated rate of N-demethylation. The unbound imipramine in plasma was diminished, but the relationship between protein-bound and unbound imipramine levels was not modified.

Animals↗

PubMed1982

Stereochemical studies of demethylated ketamine enantiomers.

The enantiomorphs of norketamine, 2-(o-chlorophenyl)-2-aminocyclohexanone, were synthesized and screened for biological activity. Resolution was achieved by fractional crystallization of the tartrate salts. Stereochemical purity was determined using standard GC or GC-MS analysis. Preliminary pharmacological evaluations revealed that intraperitoneally injected dextrorotatory norketamine caused a greater duration of loss of righting reflex in mice than the levorotatory isomer.

Anesthetics↗

PubMed1985

Pharmacodynamics of the hypnotic effect of salicylamide in rats.

Salicylamide (SAM) can produce sedation and sleep in humans and animals. To explore the potential utility of the drug as a research tool for assessing disease effects on the response of the central nervous system to depressant drugs, and to obtain a better understanding of the clinically evident sedative action of SAM, studies were performed to characterize the relationship between the concentrations and hypnotic effect of this drug in rats. Female Lewis rats weighing 170-200 g received SAM by intravenous infusion at a rate of 0.49, 1.22, or 2.47 mg/min until the onset of loss of the righting reflex. This well-defined pharmacological endpoint occurred from 16.7 +/- 2.3 min (fastest infusion rate) to 110 +/- 27 min (slowest infusion rate) after the start of the infusion. SAM concentrations at that time in serum, serum water, brain, and cerebrospinal fluid (CSF) were similar in animals that had received the 1.22- or 2.47-mg/min infusion and lower in animals that were infused at a rate of 0.49 mg/min. The slowest infusion rate group also exhibited increased serum protein binding of the drug. The SAM concentration ratio, CSF-serum water, was essentially unity in all three groups, indicative of rapid equilibration of the drug across the blood-CSF barrier. Gentisamide, the hydroxylated metabolite of SAM, was found in serum, CSF, and brain, but in low concentrations at which this metabolite alone had no hypnotic effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Pharmacodynamics of tolerance development to the anesthetic and anticonvulsant effects of phenobarbital in rats.

In this study, the potential development of tolerance towards the anesthetic and anticonvulsant effects of phenobarbital after chronic administration to rats was investigated, differentiating between dispositional and functional tolerance. Chronic exposure to phenobarbital by daily ip injections of 20 or 100 mg/kg for 14 days caused a 30% increase in clearance within 1 week. No changes occurred in the total amounts of phenobarbital and para-hydroxyphenobarbital excreted into urine and feces. Pharmacodynamic effects were quantitated after 2 weeks of treatment. The anesthetic effect was measured by slow iv infusion of phenobarbital until onset of loss of righting reflex (LRR), followed by measurement of drug concentrations in serum (both total and free), brain, and cerebrospinal fluid (CSF). With a phenobarbital dose of 100 mg/kg daily, CSF concentrations at the onset of LRR significantly increased from 136 +/- 12 to 176 +/- 21 mg/L (p less than 0.001), indicating that functional tolerance developed for the anesthetic effect. Protection of phenobarbital against convulsions induced by pentylenetetrazol (PTZ), as measured by the elevation of the PTZ plasma threshold concentration necessary to elicit seizures at the EC50 of phenobarbital, was not altered. The discrepancy observed in the development of functional adaptation of the CNS demonstrates that different mechanisms of action are reflected in the different measures of the anesthetic and anticonvulsant effects of phenobarbital that were utilized.

Anesthetics↗

PubMed1994

Kinetics of drug action in disease states. XLIII: Potentiating effect of L-tryptophan on the hypnotic action of phenobarbital and ethanol in rats.

The essential amino acid L-tryptophan has been widely used as a sleeping aid because it can produce drowsiness and decrease sleep latency. Its concentrations in plasma and brain and its binding to plasma protein are markedly altered in hepatic encephalopathy and renal failure. The purpose of this investigation was to determine if L-tryptophan can enhance the sensitivity of the central nervous system to the hypnotic actions of a barbiturate and an alcohol. Female rats weighing approximately 200 g received an intravenous infusion of L-tryptophan (0.8 or 0.08 mg/min) for 30 min and then an infusion of phenobarbital (0.824 mg/min) with L-tryptophan (0.8 or 0.08 mg min-1) until the onset of loss of righting reflex (LRR). Control animals received an infusion of saline solution for 30 min and then phenobarbital without the amino acid. Similar experiments were performed with ethanol (16.3 mg/min), with and without L-tryptophan (0.8 mg/min). L-Tryptophan infused alone at a rate of 3.8 mg/min for 84 min did not cause LRR. Administration of L-tryptophan at a rate of 0.8 mg/min with phenobarbital was associated with statistically significant reductions in the total dose and concentrations of phenobarbital in serum, serum water, brain, and cerebrospinal fluid (CSF) at onset of LRR. The 0.08 mg/min infusion of L-tryptophan had a less pronounced effect, with statistically significant reductions of phenobarbital concentrations at onset of LRR in brain and CSF. L-Tryptophan also significantly reduced the total dose and the concentrations of ethanol in serum, brain, and CSF required to produce LRR.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

GABAergic modulation of motor-driven behaviors in juvenile Drosophila and evidence for a nonbehavioral role for GABA transport.

We have identified specific GABAergic-modulated behaviors in the juvenile stage of the fruit fly, Drosophila melanogaster via systemic treatment of second instar larvae with the potent GABA transport inhibitor DL-2,4-diaminobutyric acid (DABA). DABA significantly inhibited motor-controlled body wall and mouth hook contractions and impaired rollover activity and contractile responses to touch stimulation. The perturbations in locomotion and rollover activity were reminiscent of corresponding DABA-induced deficits in locomotion and the righting reflex observed in adult flies. The effects were specific to these motor-controlled behaviors, because DABA-treated larvae responded normally in olfaction and phototaxis assays. Recovery of these behaviors was achieved by cotreatment with the vertebrate GABA(A) receptor antagonist picrotoxin. Pharmacological studies performed in vitro with plasma membrane vesicles isolated from second instar larval tissues verified the presence of high-affinity, saturable GABA uptake mechanisms. GABA uptake was also detected in plasma membrane vesicles isolated from behaviorally quiescent stages. Competitive inhibition studies of [3H]-GABA uptake into plasma membrane vesicles from larval and pupal tissues with either unlabeled GABA or the transport inhibitors DABA, nipecotic acid, or valproic acid, revealed differences in affinities. GABAergic-modulation of motor behaviors is thus conserved between the larval and adult stages of Drosophila, as well as in mammals and other vertebrate species. The pharmacological studies reveal shared conservation of GABA transport mechanisms between Drosophila and mammals, and implicate the involvement of GABA and GABA transporters in regulating physiological processes distinct from neurotransmission during behaviorally quiescent stages of development.

Age Factors↗

PubMed2001

Anticonvulsant activities of the FS-1 subfraction isolated from roots of Delphinium denudatum.

Delphinium denudatum Wall. (Ranunculaceae) is a medicinal herb used for the treatment of epilepsy in the subcontinent. The present study reports the anticonvulsant activities in the maximal electroshock test (MEST) and subcutaneous pentylenetetrazole (PTZ), bicuculline (BIC), picrotoxin (PIC)-induced seizures of the FS-1 subfraction (FS-1) that was obtained by purification of an aqueous fraction isolated from the roots of D. denudatum. In CF 1 mice, FS-1 (600 mg/kg i.p.) exhibited very potent anticonvulsant activity that was comparable to the effects of the well-known antiepileptic drug phenytoin (20 mg/kg) in MEST and protected 100% animals from hind limb tonic extension phase of this model. FS-1 also suppressed PTZ-induced threshold seizure and the loss of the righting reflex with tonic fore and hind limb extension by 100%, similar to the antiepileptic drug valproic acid (350 mg/kg). BIC-induced seizures were suppressed in 80% of the animals. FS-1 exhibited weak anticonvulsant effect on PIC-induced seizures, however, it significantly reduced mortality and delayed the onset of seizures. FS-1 had no effect on strychnine (STN)-induced extensor seizures. The results demonstrate the broad and potent anticonvulsant activity of the compounds in FS-1 of D. denudatum.

Animals↗

PubMed1993

In utero methamphetamine effects: I. Behavior and monoamine uptake sites in adult offspring.

Chronic in utero methamphetamine treatment, throughout gestation in rats, resulted in alterations in both behavior and brain monoamine function in the adult offspring. The higher dose of methamphetamine (10 mg/kg/b.i.d.) caused a significant decrease in square crossing and rearing in an open field, as well as a regional increase of serotonin and dopamine uptake sites. In contrast, the lower dose of in utero methamphetamine (2 mg/kg/b.i.d.) resulted in a significant decrease in regional densities of serotonin and dopamine uptake sites, and only decreased rearing behavior. Across treatment groups, there were significant correlations between open-field square crossing activity and the number of uptake sites in specific brain areas. Other measured behaviors, such as the neonate righting reflex and the adult Morris water maze performance, were unaffected by either in utero drug regimen. These results are discussed in terms of the known neurotoxicity of amphetamines and the ability of the immature nervous system to compensate for fetal exposure to methamphetamine.

Animals↗

PubMed1979

Prevention by diazepam of adverse effects of maternal restraint stress on postnatal development and learning in the rat.

Rats on days 12--14 of pregnancy were treated with restraint stress alone (9h daily), restraint stress plus diazepam (1 mg/kg, twice daily), diazepam alone, or left as untreated controls. Postnatal development and behaviour was assessed on a wide-ranging battery of tests. Offspring of mothers subjected to restraint stress alone were significantly retarded on a number of developmental measures including growth, ear-opening, cliff avoidance response, auditory startle response and mid-air righting reflex. When adult these offspring also showed significantly impaired learning ability in a swimming maze. However, the rate of development and learning ability in the restraint plus diazepam or diazepam alone groups was comparable to or slightly advanced of that in untreated controls. It is concluded that concurrent administration of a low dose of the tranquiliser diazepam during restraint stress prevents the adverse postnatal effects of maternal restraint stress.

Animals↗

PubMed1979

Behavioral consequences of interference with CNS development in the early fetal period.

As a part of a series of investigations into the structural and functional consequences of interference with cell proliferation, mice were treated with 5-azacytidine during two stages of early fetal life. Treatment on either the twelfth or fourteenth day of gestation led to permanent significant reductions in body weight and brain weight. Behaviorally, the earlier treatment was associated with a delay in development of the righting reflex, permanent deficits in locomotor coordination, and hypoactivity. Treatment on the fourteenth day of gestation led to decreased passive avoidance, increased active avoidance, and hyperactivity--the same syndrome observed after treatment on the eighteenth day. Both treatments led to abnormal behavior on a spatial maze task. The developmental outcome of injuries induced in the early fetal period appears similar to the outcome of injuries at later stages of development.

Animals↗