Duration Of Reflex Research Articles

Casimiroa edulis seed extracts show anticonvulsive properties in rats

A single dose of 5, 10 and 100 mg/kg of Casimiroa edulis aqueous extract (AQ); 10, 100 and 1000 mg/kg of C. edulis ethanolic extract (E-OH); in addition, 10, 30 and 12 mg/kg of propyleneglycol (Pg), phenytoin (Phen) and phenobarbital (Phb) was orally given to adult male Wistar rat groups. Thereafter, all groups were assayed for protection against maximal electroshock (MES) and pentylenetetrazole (METsc) seizure inducing tests at hourly intervals throughout 8 h. For MES, a maximal protection of 70% at the 2nd and 4th h with 10 mg/kg AQ and 100 mg/kg E-OH doses, occurred. That of Phen, Phb and Pg was 80, 90 and 10% at the 8th, 6th and 2nd h, respectively. The averaged values of the MES unprotected rats under 10 and 100 mg/kg of AQ and E-OH extracts, showed that a shortened reflex duration as well as a delayed latency and uprising times occurred. On the other hand, just an enlarged latency and no protection against METsc device in AQ and EOH was observed. Phen and Phb maximal protection was 80 and 100% at the 4th and 6th hour against METsc. Thus, AQ is tenfold more potent anticonvulsive extract than E-OH against MES.

Chronic desipramine treatment desensitizes the rat to anesthetic and antinociceptive effects of the alpha2-adrenergic agonist dexmedetomidine.

The effects of long-term administration of the tricyclic antidepressant agent desipramine on the hypnotic, antinociceptive, anesthetic-sparing, and central norepinephrine turnover suppressant action of short-term dexmedetomidine, a highly selective alpha2-adrenergic agonist, were studied in rats. Rats were given a 3- or 4-week course of twice daily administration of desipramine, 10 mg/kg, or saline. The effect of a hypnotic dose of dexmedetomidine, 250 microg/kg given intraperitoneally, on the duration of loss of righting reflex was determined. The tail flick latency response was determined before and after 50 microg/kg dexmedetomidine. The minimum anesthetic concentration of halothane and the central norepinephrine turnover rate were determined before and after administration of 30 microg/kg dexmedetomidine. Changes in the affinity and density of the alpha2-adrenergic receptor in locus coeruleus and spinal cord also were determined. Treatment with desipramine decreased dexmedetomidine-induced loss of righting reflex duration by 67% and eliminated the antinociceptive effect of dexmedetomidine. Dexmedetomidine produced a 55% decrease in minimum anesthetic concentration in the control group but no reduction in desipramine-treated rats. Desipramine did not change the receptor density or binding affinity of alpha2 receptors at the site for hypnotic (locus coeruleus) or antinociceptive (spinal cord) responses. No decrement in the central norepinephrine turnover rate was noted in the locus coeruleus of dexmedetomidine after 3 weeks of treatment with desipramine. The alpha1-adrenergic antagonist prazosin at 1 or 5 mg/kg completely (minimum anesthetic concentration reduction), almost completely (antinociceptive), or partially (hypnotic) restored responsiveness to normal. These data indicate that treatment with desipramine induces hyporesponsiveness to the hypnotic, analgesic, and minimum anesthetic concentration-reducing, but not to the suppression of central norepinephrine turnover, properties of dexmedetomidine. The hyporesponsiveness appears to involve an alpha1-adrenergic mechanism.

INTRAVENOUS ANESTHETICS INHIBIT CEREBELLAR GUANYLATE CYCLASE ENZYME

S427 INTRODUCTION: In the central nervous system, Nitric oxide (NO) mediates the action of glutamate acting at N-methyl-D-aspartate (NMDA) receptors. Pretreatment with nitric oxide synthase (NOS) enzyme inhibitors, Nomega nitro-L-arginine (NAG) and its methyl ester (NAME), augments intravenous anesthetics-induced loss of righting reflex duration [1] and hypothermia [2]. In NAME and NAG pretreated animals, cGMP inhibitory responses to anesthetics like ketamine and riluzole are augmented [3]. In an effort to elucidate the mechanisms of anesthetic interaction with NO-guanylate cyclase pathway, this study addressed the question, what is the direct effect of intravenous anesthetics on the guanylate cyclase?. METHODS: After institutional approval of the protocol, cerebellar guanylate cyclase enzyme was prepared [4] from adult male Swiss Webster mice (weight 20-25 g). An aliquot of the enzyme suspension ([similar]50 [micro sign]g of protein) was mixed in a reaction buffer containing known modulators of the enzyme (10 mM of S-Nitroso-N-acetylpenicillamine - SNAP, or theophylline) or intravenous anesthetic (100 [micro sign]M). The reaction was initiated by adding 1 mM GTP and incubating at 37[degree sign] C for 15 minutes. At the end of incubation, cGMP formed was extracted and assayed using radioimmunoassay RESULTS: Drugs used, significantly (ANOVA) modulated the enzyme activity in both soluble (F5,18 171, P < 0.0001) and particulate (F5,18 66, P < 0.0001) fractions. The NO generator, SNAP (a known stimulator of the enzyme), significantly augmented the cGMP production (P < 0.005) while, theophylline (a known inhibitor the enzyme) inhibited the cGMP production (P < 0.005) in both soluble and particulate fractions. Moreover, all the anesthetics (used in concentration closer to their clinical concentrations [similar] 50 - 100 [micro sign]M) inhibited the enzyme activity (P < 0.005) in both cytosolic and particulate fraction. (Figure 1)Figure 1DISCUSSION: Our results demonstrate that intravenous anesthetics may directly inhibit the enzyme guanylate cyclase in both soluble and particulate fractions. Soluble form is the only known receptor for NO. These results establish the enzyme guanylate cyclase as a target site for the intravenous anesthetic action.

Genetic influences on locomotor activating effects of ethanol and sodium pentobarbital

The paradoxical capability of sedative-hypnotics to produce behavioral disinhibition varies among genotypes. In DBA/2 mice ethanol (ETOH) produced strong locomotor stimulation with the peak of the biphasic curve at 1.5 g/kg IP. C57BL/6 mice showed no activation, and F 1s were intermediate. These characterizations held for a variety of behavioral indices dicices from 15 min tests, such as distance, speed, and rest time, at doses in the 0–2.0 g/kg range. Analogous studies with sodium pentobarbital (0–40 mg/kg) yielded a similar pattern of strain differences in locomotor stimulation. In contrast, loss of righting reflex durations (60 mg/kg PENTO, IP) were similar in the two strains, indicating dissociation of activating and sedative effects. In complementary studies, long- and short-sleep mice, which were bred for differences in soporific effects of ETOH, showed similar activation profiles at ETOH doses up to 1.5 g/kg and PENTO doses up to 30 mg/kg. These studies provide support for an hypothesis of common genetic control of the activation effect for ETOH and PENTO.

Temperature dependence of ethanol depression in mice: dose response.

Manipulation of body temperature during intoxication significantly alters brain sensitivity to ethanol. The current study tested the generality of this effect within the hypnotic dose range. Drug naive, male C57BL/6J mice were injected with 3.2, 3.6, or 4.0 g/kg ethanol (20% w/v) and were exposed to 1 of 7 designated temperatures from 13 degrees to 34 degrees C to manipulate body temperature during intoxication. Rectal temperature at return of righting reflex (RORR) was significantly, positively correlated with loss of righting reflex (LORR) duration and significantly, negatively correlated with blood ethanol concentration (BEC) at RORR at all three doses. These results indicate that increasing body temperature during intoxication increased ethanol sensitivity in C57 mice at all three doses tested and demonstrate the generality of temperature dependence across hypnotic doses in these animals. Interestingly, the LORR duration was dose-dependent at each ambient temperature, but the degree of body temperature change and the BEC at RORR were not dose-dependent. Overall, these results emphasize the importance of body temperature as a variable in ethanol research.

Comparisons of subcolonies of selectively bred long-sleep and short-sleep mice.

The Albany subcolony of the selectively bred Long- and Short-Sleep mice was directly compared to the original Colorado colony. As expected from the additional selection applied to the Colorado colony, small differences in the selection phenotype, loss of the righting reflex duration following ethanol treatment, were observed in the Short-Sleep line. However, no colony differences existed in three other indices of ethanol effects. Clear line differences in the shape of the locomotor activity dose-response curve, thermoregulatory effects of ethanol, and ethanol elimination rate replicated earlier findings, but these differences were similar in the two colonies. These data argue for stability of the polygenic control system and provide a picture of remarkable similarity of the two sublines, which were separated by more than 30 generations.

The Relationship between Brain Temperature during Intoxication and Ethanol Sensitivity in LS and SS Mice

The present study characterized the relationship between brain temperature, rectal temperature, and ethanol sensitivity in the selectivity bred long-sleep (LS) and short-sleep (SS) mice. Radiotelemetric brain probe implanted and nonimplanted LS/lbg and SS/lbg male mice were injected with 2.5 and 4.9 g/kg ethanol, respectively, before exposure to ambient temperatures of 15 degrees C, 22 degrees C, or 34 degrees C. Ambient temperature significantly affected rectal temperature, brain temperature, and ethanol sensitivity, measured by impairment of righting reflex. Brain and rectal temperatures at return of righting reflex (RORR) were highly correlated. In SS mice brain and rectal temperatures at RORR were significantly positively correlated with loss of righting reflex (LORR) duration and significantly negatively correlated with blood ethanol concentration (BEC) at RORR. In LS mice rectal temperature at RORR was significantly negatively correlated with LORR duration, while both brain and rectal temperature at RORR were significantly positively correlated with BEC at RORR. The strength of the correlations and r2 values generated from linear regression analysis indicates that body temperature during intoxication can explain up to 52% of the variability in ethanol sensitivity in SS mice, but only 19% of the variability in ethanol sensitivity in LS mice. The correlational analyses are consistent with previous results based on comparisons between rectal temperature and ethanol sensitivity and extend to direct brain temperature measurement the evidence that decreasing temperature during intoxication decreases ethanol sensitivity in SS mice and increases ethanol sensitivity in LS mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Potentiation by vestibular stimulation of the immobility reflex elicited by clamping in developing and adult rats

We have previously described (Exp. Neurol., 97: 315-326, 1987) that clamping of the neck elicits a profound immobility with flexion of limbs and ventroflexion of head and neck ('carrying posture'). We also observed that when a clamped rat pup is carried by the experimenter's hand, such carrying posture was potentiated. In the present paper we observed that in adult rats vestibular stimulation by circular acceleration potentiates the duration of immobility reflex by clamping and intensifies the limb flexion. In rat pups from 10 to 20 days, vestibular stimulation potentiated only the carrying posture but not the duration of the immobility reflex by clamping.

Habituation of the blink reflex: Computer assisted quantitative analysis

The electrically evoked blink reflex (BR) was elicited in 20 healthy volunteers, varying the stimulus interval by a computer JN 110. Latencies, amplitudes, reflex duration and reflex areas of early and late components of the BR were analysed by a computer program testing the signal-to-noise ratio, the response configuration and frequency distribution. Changes in habituation related to the stimulus interval can be illustrated best by the progressive diminution of R2 areas. Computing the habituation in relation to the stimulation frequency by a standardized program seems to be a quantitative method to assess habituation in various diseases and during treatment studies.

Visually monitored postrotary nystagmus in seven autistic children.

Therapists who evaluate the sensorimotor functions of autistic children have become increasingly interested in monitoring their responses to vestibular stimulation. In this study, the duration of the nystagmus reflex is visually monitored and then measured by means of a stop-watch. Each of 7 autistic subjects received 18 sessions (36 trials) of horizontal semicircular canal stimulation during a period of 25 days. In each trial a graduated acceleration in a hand operated rotating chair preceded an abrupt stop, with a rapid deceleration from 180 degrees/second to 0 degree/second. Although subject option (intentional response) imposes limitations on the data interpretation, inspection of the nystagmus functions over time suggests the following: substantial trial-to-trial variability; substantial subject-to-subject variability; greater scores following trials to the subjects' left (the direction of the second trial in each session) than to the right (the direction of the first); and no evidence of consistent change for most subjects in nystagmus duration across the 36 trials. Implications for clinical evaluation of nystagmus are discussed.

Depth-duration profile of the immobility reflex: theoretical implications for its triggering, sustaining, and terminating mechanisms.

Immobility reflex (IR) durations of rabbits were remarkably consistent (weighted average range of 0.36-0.70 minutes/trial), under the special conditions when rabbits were "habituated" by approximately 25 preliminary trials and when termination of IR was operationally defined as the point at which any attempt, even abortive, at righting occurred. When the mean duration for each rabbit was normalized (into quartile duration points) and then rabbits were tested at these points to determine arousal threshold, each rabbit revealed a clear progressive decrease in the "depth" of IR as the duration of a given episode progressed. Both duration and depth were decreased when body hair was removed. The hippocampal EEg revealed persistent theta activity throughout a given trial; but the specific frequency of theta increased briefly just prior to induction of IR and decreased immediately afterwards. In short-duration trials, theta frequency increased progressively until the IR terminated spontaneously. In long-duration trials frequency changes oscillated. Each of these observations is interpreted to support the theory that, during IR, reverberating neural circuits (in the brainstem reticular formation) are activated and their output inhibits spinal motor neurons.

Effects of α-agonists on circulatory responses to somatic afferent nerve stimulation

The effect of intracisternal (i.c.m.) injection of clonidine, noradrenaline, and piperoxane on the pressor response to electrical stimulation of a peripheral somatic afferent nerve was investigated using anaesthetized cats. It was found that noradrenaline caused a depression of the magnitude of the pressor response and this effect was antagonized by subsequent injection of piperoxane i.c.m. In contrast, clonidine had no significant effect on the magnitude of the somatic pressor reflex but caused a dose-dependent prolongation of the reflex after cessation of nerve stimulation. This prolongation was antagonized by piperoxane which also caused an increase in the magnitude of the reflex. Piperoxane alone had no significant effect on the magnitude or duration of the reflex. Neither magnitude nor duration of the somatic pressor reflex was influenced significantly by a reduction in resting blood pressure. It is suggested that clonidine and noradrenaline act at different sites within the central nervous system to produce qualitatively changes in the efferent sympathetic discharge pattern modulating the somatic pressor reflex.

The effect of induced hyperthermia on the blink reflex in multiple sclerosis.

In 76 patients with multiple sclerosis, the blink reflex was elicted electrically at normal body temperature and during induced hyperthermia to observe the effect on conduction within the reflex pathway through the brainstem. Special attention was directed to 31 patients with electrophysiologic evidence of reflex slowing, presumably because of demyelination in the reflex pathway. Hyperthermia did not induce any significant changes in mean reflex latency, amplitude, or duration in either the overall group of 76 or in the 31 patients with baseline blink reflex abnormalities. While the mean reflex latency did not change, 13 (33 percent) of 39 abnormal R1 responses from the 31 patients changed by 1.5 msec or more during hyperthermia, whereas change of similar magnitude was noted in only three (3 percent) of 90 normal R1 responses.

The significance of bladder capacity under aspect of continence and micturition in neurogenic bladder dysfunction.

The bladder capacity of patients with a neurogenic bladder disorder was determined. Since the bladder capacity varies according to the type of neurogenic lesion (supranuclear, infranuclear), it was to be determined, whether reflex detrusor activity and duration of the lesion would influence bladder capacity. It was found that in supranuclear lesions s sufficient bladder capacity can be maintained with a balanced micturition, and that spincterotomy does not result in reduced bladder capacity. In infranuclear lesions intermittent catheterization is a good therapeutic method to preserve continence and an intact renal function as well.

Effect of Long-Term Haemodialysis on the Duration of Ankle Reflex: Further Evidence That Haemodialysis May Cause Hypothyroidism

Effect of Long-Term Haemodialysis on the Duration of Ankle Reflex: Further Evidence That Haemodialysis May Cause Hypothyroidism

Septal- and caudate-induced behavioral inhibition in relation to hippocampal EEG of rabbits

These experiments examined behavioral inhibition in rabbits by comparing low and high frequency electrical stimulation of the septum and the caudate nucleus on 3 measures of unlearned activity, a discriminative active avoidance task, and a lever-press operant task. Four and 8/sec stimulation of either site evoked a sustained rhythmic discharge in the hippocampus morphologically similar to naturally occurring theta rhythm. At 100/sec, the EEG was persistently desynchronized by septal stimulation and generally unaffected by caudate stimulation. Septal stimulation at all frequencies caused massive increases in exploratory activity in some rabbits but had no clear effect on jiggle stand activity or on duration of immobility reflex (animal hypnosis). Both septal and caudate stimulation inhibited previously learned avoidance and operant behavior, and these effects were frequency specific occurring at low, but not high, stimulus frequencies. Caudate stimulation also inhibited jiggle stand activity and exploration, and enhanced the immobility reflex.

Cerebellar influence on the micturition reflex

Evoked cortical responses were recordable in the anterior vermis of the cerebellum by stimulation of the pelvic detrusor nerve and the portion of the pudendal nerve innervating the external urinary sphincter. Electrical stimulation of the fastigial nucleus depressed the micturition reflex by depressing pelvic motor nerve activity leaving afferent pelvic nerve activity unaffected. Ablation of the anterior vermis in the supracollicular decerebrate cat resulted in a hyperactive micturition reflex with increase in reflex duration. The experimental evidence indicated the cerebellum has a tonic depressant effect on the micturition reflex which is organized in the pontine mesencephalic reticular formation.

Relationships between Several Indices of Acoustic Reflex Function and Susceptibility to Temporary Threshold Shift Produced by Different Spacings of Impulsive Noise and by Continuous Noise

Temporary threshold shift (TTS) was measured following exposure, on separate days, to 110 dB thermal noise or to 20 successive 166-dB-peak, 58-μsec-duration, spark-gap-produced impulsive noises, spaced 0.2, 2.0, or 10.0 sec apart. Pearson correlations were calculated between these measures and estimates of acoustic intratympanic reflex thresholds, durations, rise times, and decay times, obtained with a Madsen impedance bridge and averaged over 10 trials at each of three eliciting frequencies on an averaging computer. There were indications of negative correlations of reflex duration and TTS and of positive correlations of reflex threshold and TTS, especially at the 2.0-sec impulse spacing.

Function laws of reflex duration under various conditions and their relation to function laws of ganglia cells

Fruhere Untersuchungen hatten ergeben, das die Funktions- und Erholungsfahigkeit der Vorderhornganglienzelle im Aortenabklemmversuch quantitativ exakt bestimmt werden konnen. Da es gelang, bestimmte, mathematisch formulierbare Gesetzmasigkeiten zu entwickeln, die die Anderung dieser Funktionsgrosen unter verschiedenen physiologischen Bedingungen beschreiben, und da bei diesen Versuchen Funktions-und Schwunddauer des Quadricepseigenreflexes als Mas fur die Funktions- und Erholungsfahigkeit verwandt wurde, schien es prufenswert, ob die zeitlichen Komponenten des Reflexablaufes und die Reflexhohe untereinander eine gesetzmasige Verknupfung aufweisen und ob Beziehungen dieser Funktionsablaufe zu den bereits gefundenen Funktionsgesetzen der Ganglienzelle bestehen. In einer neuen Serie von 10 Kaninchenversuchen wurden, auser den zeitlichen Funktionsgrosen der Ganglienzelle, der maximalen Funktionszeit Fm und der zugehorigen Schwundzeit SFm, die Reflexzeit tr, die Anstiegsdauer ta, die Zuckungshohe h und die Gesamtzuckungsdauer tg von 325 Reflexzuckungen bestimmt.

On the responses to environmental stimuli, and the sensory physiology of Millipedes (Diplopoda).

SUMMARY.The behaviour and sensory physiology of Paradesmus gracilis (C. L. Koch) and Blaninlus guttulatus (Bose) have been investigated. Both species posses a dermal light sense, and respond to light stimuli by means of a simple orthokinesis. Their temperature reactions fall into three categories: a general orthokinetic metabolic effect upon speed of locomotion, duration of spiral reflex, etc., a preference shown klinokinetically for temperatures about 15°C.; and orthokinetic activity stimulated by sudden drops in temperature. The temperature sense cannot be aseribed to any particular sensillae, but resides in the antennae as well as elsewhere. Positive geotaxis become apparent under the influence of the orthokinesis engendered by desiceation. The Tömösvary organs may be gravity receptors, but if so the stimulation of various proprioceptive organs by the weight of the body acting on limtes is probably also concerned in the reception of the stimulus.No orthokinetic response to humidity comparable with that found in woodlice and wireworms has been observed: the millipedes show maximum locomotory activity at all humidity ranges, but once they have finally come to rest, they do not readily start moving again. Responses to moisture, however, are far more important in their behaviour; they are purely orthokinetic, and probably a general effect of dehydration. Possibly both Tömösvary organs and trichoid sensillae register vibrations: the millipedes respond by curling up (spiral reflex), but very slight vibrations frequently stimulate locomotory activity. Reactions to contact stimuli are of very great significance in the behaviour of millipedes. They are chiefly orthokinetic, and the tactile hairs on the limbs, sides of the body, and particularly on the antennae are the sensory receptors.Millipedes do not respond to odours, but there is an orthokinetic “attraction” to gluclose and sucrose with a threshold about 0·5 gm. litre. There is no attraction to asparagine and strach, but urea repels Blavials. Antennary and gnathochilarial basiconic sensillae are the receptors for contact chemical stimulation. Removal of, or painting over the antennae induces a state of depression which persists until death.The significance of the behaviour and sensory responses of millipedes in relation to their ecology is discussed with particular reference to the importance of Blaniulus as an agricultural pest.