[RIGHTING REFLEX IN THE RABBIT DURING BRIEF PERIODS OF SUBGRAVITY].
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Animals↗
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[EFFECT OF CHLOROFORM, ETHER AND COMBINATIONS OF ETHER AND AMINAZIN (CHLORPROMAZINE HYDROCHLORIDE) ON THE RIGHTING REFLEX IN BIRDS WITH LIMITED INJURIES OF THE FOREBRAIN AND MIDBRAIN].
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Anesthesia↗
The relative reliability of the escape reaction and righting-reflex sleeping times in the mouse.
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Animals↗
On postural and righting reflexes.
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Humans↗
Transcranial electrical stimulation (Limoge's currents) potentiates the inhibition of righting reflex induced by droperidol in rats.
The effects of transcranial electrical stimulation (TCES) on droperidol-treated rats were evaluated using the righting reflex latency (RRL) test. TCES (high frequency (HF)-166 kHz, intermittent-100 Hz current) delivered through three electrodes (a negative electrode placed between the eyebrows and positive electrodes located in the retro-mastoid region) was shown to potentiate the inhibition of righting reflex induced by droperidol. This potentiation was found to depend on the dose of the drug, the characteristics of the current delivered and the duration of stimulation. We also observed that TCES-induced potentiation of inhibition of righting reflex produced by droperidol injection was not reversed: (i) after naltrexone administration, (ii) when measures were performed on p-chlorophenylalanine (pCPA)-treated animals. These results suggest that, under the experimental conditions: (i) TCES does not interact with opioid endogenous to potentiate droperidol effects, (ii) the effect of TCES on dopaminergic system prevails against TCES action on serotonergic system. Though these findings enlarge the comprehension of TCES effects on the central nervous system, further investigations are necessary to elucidate TCES mechanisms.
Animals↗
Development of the air righting reflex in cats visually deprived since birth.
Classical experiments on the ability of cats to turn in the air during a free fall, the air righting reflex, have shown that vestibular and visual cues can play a role in this behavior. The development of this air righting reflex in kittens blinded since birth has been studied. The results show that the development in the blinded kittens is the same as in normal kittens with vision: mature by 33 days. This result and the comparison with other studies confirm that the air righting reflex is primarily a vestibular controlled reaction.
Animals↗
Application of serial sampling of cerebrospinal fluid in pharmacodynamic studies with a drug active in the CNS: heptabarbital concentrations at onset and offset of loss of righting reflex in rats.
As cerebrospinal fluid (CSF) possesses unique characteristics in order to explore concentration-pharmacological response relationships of drugs active in the CNS, the practicability of serial sampling of CSF was tested in a study with heptabarbital. Concentrations in CSF and plasma were measured simultaneously in individual rats during and after an intravenous infusion for 30 min. At the end of the infusion, the distribution equilibrium was attained with a CSF/plasma concentration ratio of 0.38, roughly equal to the fraction unbound to protein. When concentrations in blood and CSF were determined at the onset and offset of loss of righting reflex concentrations in blood were significantly greater at onset (146 +/- 19 mg/l) than at offset (108 +/- 16 mg/l, n = 6), whereas concentrations in CSF were identical (39 +/- 5 and 38 +/- 5 mg/l, respectively). This confirmed the earlier observation that the CSF is pharmacokinetically indistinguishable from the site of action. When the duration of the loss of righting reflex was varied, concentrations of heptabarbital in CSF at onset and offset were similar, independent of the duration of the loss of righting reflex (1-5 hr). These findings demonstrate the absence of the development of acute tolerance and confirmed that no (inter)active metabolites interfered with the pharmacological response. In a total number of 26 rats the concentrations in CSF at onset and offset of loss of the righting reflex were compared. The interindividual variation was 13-15% and the intra-individual variation was only 4-6%. The results demonstrate the usefulness of serial sampling of CSF in pharmacodynamic studies with centrally acting drugs.
Animals↗
Stereoselective loss of righting reflex in rats by isoflurane.
BACKGROUND: Although it is accepted widely that optically active intravenous general anesthetics produce stereoselective effects in animals, the situation regarding volatile agents is confused. Conventional studies with scarce isoflurane enantiomers have been limited to small numbers of animals and produced conflicting results. By injecting these volatile enantiomers intravenously, however, it is possible to study large numbers of animals and obtain reliable results that can help to identify the molecular targets for isoflurane. METHODS: Pure isoflurane enantiomers were administered intravenously to rats after solubilization in a lipid emulsion. The ability of each enantiomer to produce a loss of righting reflex was determined as a function of dose, and quantal dose-response curves were constructed. In addition, sleep times were recorded with each enantiomer. Chiral gas chromatography was used to measure relative enantiomer concentrations in the brains of rats injected with racemic isoflurane. RESULTS: The S(+)-enantiomer was 40 +/- 8% more potent than the R(-)-enantiomer at producing a loss of righting reflex. The S(+)-enantiomer induced longer sleep times (by about 50%) than did the R(-)-enantiomer. Rats anesthetized by a dose of racemic isoflurane sufficient to achieve a half-maximal effect had essentially identical brain concentrations of the two enantiomers. CONCLUSIONS: The S(+)-enantiomer of the general anesthetic isoflurane is significantly (P < 0.001) more potent than the R(-)-enantiomer at causing a loss of righting reflex in rats. This confirms the view that isoflurane acts by binding to chiral sites. The observed degree of stereoselectivity provides a useful guide for ascertaining from in vitro experiments which molecular targets are most likely to play major roles in the loss of righting reflex caused by isoflurane.
Anesthetics, Inhalation↗
Permissive role of brain allopregnanolone content in the regulation of pentobarbital-induced righting reflex loss.
Allopregnanolone [3alpha-hydroxy-5alpha-pregnan-20-one] (ALLO), a potent neurosteroid that positively modulates gamma-aminobutyric acid (GABA) action at various GABA(A) receptor subtypes is synthesized in nanomolar concentrations and stored non uniformly in various brain structures of mammals. We have measured brain ALLO content and its precursors by negative ion chemical ionization-mass-spectrometry after purification and separation of the different steroids with HPLC and gas chromatography. Our procedure measures steroids in the femtomolar range with structural information and unsurpassed selectivity. We were able to establish an association between the decrease in content of ALLO in mouse brain cortex elicited by either long-lasting social isolation or by the administration of 17beta-17 [bis (1-methylethyl) amino carbonyl] androstane-3,5-dilene-3-carboxylic acid (SKF 105111). an inhibitor of Types I and II 5alpha reductases, and the shortening of the righting reflex loss elicited by pentobarbital (PBT). SKF 105111 added to cortical brain slices in concentrations up to 10(-5) M failed per se to alter GABAergic currents or their potentiation by PTB recorded from pyramidal neurons. Fluoxetine (1.45 or 2.9 micromol/kg i.p.) doses that fail to change the PTB-induced loss of righting reflex and the level of brain ALLO in group-housed mice normalized both parameters in socially-isolated mice. In addition, we could detect both fluoxetine actions in socially isolated mice pretreated with doses of p-chlorophenylalanine (1.2 mmol/kg i.p. at 72, 48, and 24 h) that substantially inhibit brain serotonin 5HT synthesis as shown by an 80% drop of brain 5HT content. These studies for the first time have provided evidence suggesting that the endogenous cortical stores of ALLO physiologically upregulate GABAergic tone and by such a mechanism play a permissive or facilitatory role on the PTB-induced loss of the righting reflex. In the absence of such a permissive physiological influence by endogenous ALLO, the righting reflex inhibition by PTB is down regulated.
5-alpha Reductase Inhibitors↗
Development of righting when falling from a bipedal standing posture: evidence for the dissociation of dynamic and static righting reflexes in rats.
Righting to prone when placed supine on the ground by rats is present at birth, albeit in incomplete form. In contrast, righting in the air when falling from the supine position does not begin to emerge until the end of the first week and is not complete until the end of the third week postnatally. On the ground, the animals have sensory information from proprioceptive-tactile sources, as well as vestibular; in the air, they have only vestibular. Thus, it is possible that the difference between contact righting and air righting is a reflection of the relative difference in the maturation of tactile vs. vestibular mechanisms. In this study, pups were tested by pushing them backwards from a bipedal standing position. Such a context provided proprioceptive-tactile information during the fall. The results showed that the developmental onset and maturation of righting from the bipedal position resembled that of air righting rather than contact righting. This suggests that the difference between air righting and contact righting is not due to differences in sensory inputs, but to differential maturation of neural mechanisms for acceleratory (i.e., falling) vs. stationary (i.e., lying on the ground) forms of righting. That is, the appropriate neural systems are organized for the type of righting, not for the sensory systems used. Even so, some evidence is provided suggesting a developmental dissociation between righting from falling with vestibular information only, and with proprioceptive-tactile information in addition. Therefore, righting systems appear to need two dimensions of classification--one based on sensory systems involved, and the other in terms of the context of righting (i.e., falling vs. stationary).
Aging↗
Abnormal air-righting reflex in striatal rats.
To understand dynamic postural control of the higher brain, we compared air-righting reflexes in various decerebrate rats. Post-operative 3-5 d thalamic and mesencephalic rats displayed almost similar righting movements as intact. However, in striatal animals, coordination of righting movements was disrupted. The higher brain without cortical control could interfere with the brainstem center of the air-righting reflex.
Animals↗
Kinetics of drug action in disease states. V. Acute effect of urea infusion on phenobarbital concentrations in rats at onset of loss of righting reflex.
It has been reported that patients suffering from azotemia attributable to urinary obstruction required significantly less thiopental for induction and maintenance of general anesthesia than did a comparable group of patients with normal blood urea concentrations. Moreover, the thiopental requirements of normal subjects could be reduced by urea administration. In rats, experimental renal dysfunction was associated with reduced concentrations of phenobarbital (PB) in serum, serum water, brain and cerebro-spinal fluid at onset of a defined hypnotic effect (loss of righting reflex) produced by a slow i.v. infusion of PB. To determine the mechanism of this effect, these studies have now been repeated in normal rats made azotemic (approximately 170 mg of urea nitrogen/100 ml of serum) by intra-arterial infusion of urea and in control animals infused with saline solution. The total dose of thiopental required to produce loss of righting reflex was significantly reduced in the rats infused with urea. confirming the clinical observations. Similar results were obtained with PB and heptabarbital, two barbiturates that (unlike thiopental) are not racemic mixtures and are therefore more suitable for this investigation. On the other hand, urea infusion had no apparent effect on the concentrations of PB and heptabarbital in serum, brain and cerebrospinal fluid at onset of loss of righting reflex. Urea apparently affects the distribution kinetics of barbiturates and this, rather than increased receptor sensitivity, appears to be responsible for the decreased barbiturate dose requirements in acute experimental azotemia produced by urea infusion.
Animals↗
Sleep deprivation potentiates the onset and duration of loss of righting reflex induced by propofol and isoflurane.
BACKGROUND: Sleep and anesthesia differ physiologically but produce a similar loss of responsiveness to environmental stimuli. Recent data suggest that neuronal networks active in naturally occurring sleep also play a role in the anesthetized state. Changes in the propensity to sleep may then modify the response to anesthetic agents. The authors tested the hypothesis that sleep-deprived rats would require less anesthetic than rested rats to achieve a similar loss of responsiveness. METHODS: Rats were subjected to a 24-h period of either sleep deprivation or ad libitum activity. Sleep deprivation was produced by placing rats on a disk that rotated when sleep was detected by electroencephalographic and electromyographic (EEG, EMG) monitoring. A fixed dose of anesthetic agent was then administered, and the time required to induce loss of righting reflex was measured. Anesthetic administration was then stopped, and the time to recovery measured. All rats received both treatments separated by 7 days. RESULTS: Sleep deprivation reduced the time to loss of righting reflex by 40% for propofol (P < 0.025) and 55% for isoflurane (P < 0.025) and prolonged the time to recovery. In a separate control experiment, exposure to the deprivation environment but with disk rotation modified to allow adequate sleep did not affect the response to anesthetic administration. CONCLUSIONS: Sleep deprivation significantly potentiated the ability of inhaled and intravenous anesthetic agents to induce a loss of righting reflex. These results support the hypothesis that neuronal networks active in sleep are also involved in the anesthetized state and suggest that sleep deprivation may partly explain the variability in patient response to anesthesia.
Administration, Inhalation↗
Effect of isoflurane and other potent inhaled anesthetics on minimum alveolar concentration, learning, and the righting reflex in mice engineered to express alpha1 gamma-aminobutyric acid type A receptors unresponsive to isoflurane.
BACKGROUND: Enhancement of the function of gamma-aminobutyric acid type A receptors containing the alpha1 subunit may underlie a portion of inhaled anesthetic action. To test this, the authors created gene knock-in mice harboring mutations that render the receptors insensitive to isoflurane while preserving sensitivity to halothane. METHODS: The authors recorded miniature inhibitory synaptic currents in hippocampal neurons from hippocampal slices from knock-in and wild-type mice. They also determined the minimum alveolar concentration (MAC), and the concentration at which 50% of animals lost their righting reflexes and which suppressed pavlovian fear conditioning to tone and context in both genotypes. RESULTS: Miniature inhibitory postsynaptic currents decayed more rapidly in interneurons and CA1 pyramidal cells from the knock-in mice compared with wild-type animals. Isoflurane (0.5-1 MAC) prolonged the decay phase of miniature inhibitory postsynaptic currents in neurons of the wild-type mice, but this effect was significantly reduced in neurons from knock-in mice. Halothane (1 MAC) slowed the decay of miniature inhibitory postsynaptic current in both genotypes. The homozygous knock-in mice were more resistant than wild-type controls to loss of righting reflexes induced by isoflurane and enflurane, but not to halothane. The MAC for isoflurane, desflurane, and halothane did not differ between knock-in and wild-type mice. The knock-in mice and wild-type mice did not differ in their sensitivity to isoflurane for fear conditioning. CONCLUSIONS: gamma-Aminobutyric acid type A receptors containing the alpha1 subunit participate in the inhibition of the righting reflexes by isoflurane and enflurane. They are not, however, involved in the amnestic effect of isoflurane or immobilizing actions of inhaled agents.
Anesthetics, Inhalation↗
[Development of righting reflexes and their influence on the development of static functions in children with infantile cerebral palsy].
In a group of 55 children with signs of central nervous system lesions the development of righting reflexes and static functions was observed during the first 3 years of life. A delay and disturbances in the development of righting reflexes and static functions was observed with differences between the individual groups of infantile cerebral palsy.
Age Factors↗
Cyclooxygenase-1 inhibition shortens the duration of diazepam-induced loss of righting reflex in mice.
Cyclooxygenase-1 (COX-1) inhibition by a selective inhibitor valeryl salicylate, or nonselective inhibitors at 10 mg/kg, including aspirin, ibuprofen, indomethacin, and picroxicam, attenuated by 29%-46% the duration of loss of righting reflex induced by diazepam (20 mg/kg) in mice. On the other hand, arachidonic acid (20 mg/kg) increased the duration of diazepam-induced loss of righting reflex by 48%. This effect of arachidonic acid was abolished by aspirin. However, aspirin at 10 mg/kg also did not alter the effects of diazepam (5 mg/kg) on spontaneous activity and rotarod performance. These findings strongly suggest that one or more COX products, most likely prostaglandins, play a significant role in modulating the hypnotic effect of diazepam. Elucidating the mechanism involved may further our understanding of the pharmacology of benzodiazepines.
Animals↗
Kinetics of drug action in disease states. IV. Effect of pregnancy on phenobarbital concentrations at onset of loss of righting reflex in rats.
This investigation was designed to determine if the acute hypnotic activity of a barbiturate is altered by advanced pregnancy. Twenty-day-pregnant rats and nonpregnant rats of the same age received an i.v. infusion of phenobarbital, 0.824 mg/min/rat, until they lost their righting reflex. The concentrations of total and free phenobarbital in serum at that time were significantly lower in pregnant than in nonpregnant animals. However, pregnancy had no effect on the concentrations of phenobarbital in the brain and cerebrospinal fluid at onset of loss of righting reflex. The difference of the serum phenobarbital concentrations was due to the slower rate of phenobarbital infusion received by the pregnant rats when normalized for body weight. The lack of difference of phenobarbital concentrations in cerebrospinal fluid, a site that reflects the concentration of the free drug at the sites of action, indicates that advanced pregnancy has no apparent effect on the central nervous system response to phenobarbital.
Animals↗
Similar development of tolerance to barbital-induced inhibition of avoidance behavior and loss of righting reflex in rats.
In order to determine if tolerance develops to the inhibition of avoidance behavior by the barbiturates, the effects of barbital on avoidance were determined in rats given barbital in their sole source of drinking water for 7 or 33 days. For comparison tolerance to the loss of righting reflex was also determined in other rats at the same time. All rats were trained by one 60-min session in a one-way active avoidance task; they were then put on the chronic drug administration schedule and then tested on the appropriate day after a single IP injection of 250 mg/kg sodium barbital. To assess the degree of tolerance, the brain level of barbital found at the biological endpoint--the loss of avoidance or loss of righting reflex--was compared in the chronic barbital treated rats and controls. A similar degree of tolerance developed to both effects of the drug and it appeared to be as great after 7 as after 33 days of chronic barbital treatment.
Animals↗