Reflex Properties Research Articles

Cardiovascular functions of brain serotonergic neurons in the rabbit as analysed from the acute and chronic effects of 5,6-dihydroxytryptamine.

The effects of intracisternal (i.c.) 5,6-dihydroxytryptamine (5,6-DHT) or creatinine sulphate vehicle on mean arterial pressure (MAP), heart rate, and baroreceptor-heart rate and nasopharyngeal reflex properties were studied in conscious rabbits. For the baroreflex we derived sigmoid MAP-heart period (HP) curves, and for the nasopharyngeal reflex we measured apnea time, rise in HP, and delta MAP. The acute effects occurring over the first few hours in intact and decerebrate rabbits included: (a) tachycardia and a decrease in baroreflex HP range and gain, which were mediated through bulbar or spinal pathways influencing vagal motoneurons; (b) a transient early rise in MAP through a bulbar or spinal pathway and a late suprapontine rise in MAP; and (c) shorter apnea time, less bradycardia, and less well-maintained MAP during nasopharyngeal stimulation. By day 14, when spinal cord serotonin was depleted by 70%, resting MAP and heart rate had recovered, HP range and gain had risen above initial control, but nasopharyngeal apnea time and bradycardia were still reduced. Some of the acute responses were due to synaptic release of serotonin (5HT); since the tachycardia and late component of the pressor response were blocked by pretreatment with i.c. methysergide, the acute changes in baroreflex parameters were opposite to the chronic changes, and a second injection of 5,6-DHT failed to produce these changes. On the other hand, the acute and chronic nasopharyngeal responses were similar, suggesting that the former were due to neuronal block and not 5HT release. These findings indicate that central serotonergic neurons inhibit cardiac vagal activity, increase blood pressure through both suprapontine and bulbar or spinal pathways, and are involved in the nasopharyngeal reflex.

Effects of ketamine and althesin anesthesia on baroreceptor-heart rate reflex and hemodynamics of intact and pontine rabbits

The changes in baroreceptor-heart rate reflex properties and in hemodynamics produced by light ketamine anesthesia were studied in one group of rabbits before and after infracollicular decerebration and those produced by Althesin anesthesia in another group. Ketamine produced marked depression of baroreceptor reflex-mediated vagal effects on heart rate which was of similar magnitude in intact and pontine decerebrate rabbits; this indicates that its action was largely at or below the pons. Althesin produced much less vagal depression than ketamine in the intact rabbit but in pontine rabbits the depression was greatly enhanced. The smaller vagal depression in the intact rabbit appears to be due to a facilitatory effect through a suprapontine pathway by Althesin which partially masks its depressant effect below the pons. In the intact rabbit ketamine produced a greater rise in blood pressure than Althesin anesthesia for 1 h; the greater pressor response was due to a transient rise in total peripheral resistance (TPR) and a sustained rise in cardiac output. The difference in the blood pressure responses was mainly due to differences in action of the two anesthetics at or below the pons and only the transient rise in TPR during ketamine anesthesia was mediated through a suprapontine pathway.

Effects of noradrenergic and serotonergic neurons on blood pressure, heart rate and baroreceptor-heart rate reflex of the conscious rabbit.

The acute and chronic effects of intracisternal (i.c.) 6-hydroxydopamine (6-OHDA) and 5,6-dihydroxytryptamine (5,6-DHT) on mean arterial pressure (MAP), heart rate, and baroreceptor-heart rate reflex properties were examined in conscious rabbits. The reflex was studied by deriving MAP-heart period (HP, pulse interval) curves. The acute effects occurring over the first few hours were due to release of transmitter (noradrenaline after 6-OHDA; serotonin after 5,6-DHT) from specific synaptic sites; the changes on day 14 were due to destruction of specific neurons. Noradrenergic bulbar neurons facilitate vagal heart rate motoneurons and serotonergic neurons have an inhibitory effect. Noradrenergic bulbospinal pathways have a depressor effect on MAP and serotonergic bulbospinal activity increases MAP. These effects on heart rate and MAP were mediated through independent parallel pathways. The acute circulatory changes due to each neurotoxin also included a long latency pressor component, which was mediated through a pathway where a serotonergic neuron was in series with a noradrenergic neuron which sends fibers to a suprapontine pressor site. There were no chronic changes in resting MAP or heart rate, but chronic changes in reflex HP range and gain were opposite to the acute effects of transmitter release. These findings indicate that noradrenergic and serotonergic neurons normally participate in the central baroreceptor-heart rate reflex pathways of the intact animal.

Role of baroreceptor reflexes in the hemodynamic and heart rate responses to althesin, ketamine and thiopentone anesthesia

The effects of i.v. infusions of althesin, ketamine and thiopentone were studied in instrumented rabbits, in doses that produced similar levels of light anesthesia. The main hemodynamic differences were in the rises in mean arterial pressure (MAP) and in total peripheral resistance (TPR) which were in the order of ketamine > thiopentone > althesin. These rises in MAP and TPR did not occur in sino-aortic denervated rabbits suggesting that in normal rabbits these depended on the integrity of the arterial baroreceptors and/or chemoreceptors. The heart rate increased with all anesthetics mainly owing to reduction in vagal efferent activity, except with althesin where cardiac sympathetic activity increased also. Baroreceptor—heart rate reflex properties were studied by deriving sogmoid curves relating MAP to heart period (HP, i.e. pulse interval). All drugs depressed the following curve parameters: (i) HP range, i.e. the difference in HP plateaux from maximal tachycardia to maximal bradycardia; and (ii) the reflex gain (sensitivity). The order of depression was ketamine > thiopentone > althesin, i.e. the same as the order in which they evoked pressor effects. The results suggest that the 3 anesthetics produce differing depression of afferent mechanisms related to baroreceptor reflexes and that this accounts for both the differences in pressor effects (through disinhibition of constrictor tone) and in depression of the vagal and sympathetic components of the baroreceptor—heart rate reflex.

The history of the concept of motivation.

Explanations and postulated mechanisms of motivation are traced from Hobbes to current cognitive formulations. Beginning with the hedonic principle, succeeding explanations of motivation have included drive theory, in terms of reflexive properties and in the Freudian notion of unconscious motivation, and current cognitive explanations, which have not yet been fully developed. It is hoped that the repeating cycle from rationality to irrationality and over again can be avoided in future explanations.

The central nervous system and its operation in cardiovascular control.

In the intact organism environmental disturbances affecting the circulation often result in simultaneous changes of several groups of peripheral afferents. These elicit characteristic patterns of autonomic activity with distinctive patterns of vagal activity, of regional sympathetic neural activity and of adrenal catecholamine secretion. During simultaneous changes in several groups of afferents the autonomic responses are often non-linear, with the response to one input markedly influenced by the level of the others. When these non-linear interactions involve the central arterial baroreflex pathways the properties of the body's blood pressure system can become greatly altered. With certain combinations of afferents these interactions make it possible for the organism to better withstand large perturbations than it could do through the normal properties of the arterial baroreceptor reflex. The different neuron groups contributing to the CNS autonomic pathways release many different transmitters including noradrenaline or serotonin and changes in reflex properties result from alterations in transmitter release in one or other of the pathways of the particular network. The peripheral arterial baroreceptors become rapidly reset during sustained alterations in blood pressure. Their 'memory' for any given absolute blood pressure is only a few minutes duration. Hence sustained changes in autonomic activity depend on the properties of the CNS either through signals arising from other groups of peripheral receptors, from central 'command' or owing to changes in transmitter release in a given pathway.

C 11 Contractions are Reflexive

It is shown that a completely nonunitary Cl I contraction defined on a separable Hilbert space with finite defect indices is reflexive. In this note, only bounded linear operators defined on complex, separable Hilbert spaces will be considered. A contraction T (11 TII 0 and T*nx -+-> 0 for any x # 0. It is well known that such a contraction is quasi-similar to a unitary operator. Since unitary operators (even normal operators) are reflexive (cf. [3]), the question arises: Is the property of reflexivity preserved under the quasi-similarity? In other words, is a C11 contraction reflexive? In the present note we show that the answer is affirmative if the C11 contraction is completely nonunitary (c.n.u.) and has finite defect indices. We conjecture that the general case is also true. Recall that a contraction T is c.n.u. if there is no nontrivial reducing subspace on which T is unitary. The defect indices of T are, by definition, dT = dim[(1 T*T )1/29C ] , d7, = dim[(I TT*)1/29C]. If T is of class C11, then dT = dT*. In the following discussion we shall make use of the functional model for contractions developed by Sz.-Nazy and Foia? (cf. [4]). More specifically, if T is a c.n.u. contraction with dT = dT = n < oo, then T can be considered as defined on H = [Hn 2 2L, ] e {OTW @ Aw: w E H 2) by T(f @ g) = P(e'tf @ e"g) for f ED g E H, where Ln2 and Hn2 denote the standard Lebesgue and Hardy spaces of Cn-valued functions defined on the unit circle, EJT iS the characteristic function of T, A = (1 -_ *ET)1/2 and P denotes the (orthogonal) projection onto H. Any operator S in { T}', the commutant of T, has the form P[A ?], where A is a bounded analytic function while B and C are bounded measurable functions satisfying AeOT = OTAO and BET + CA = AA0 for some bounded analytic function A0 (cf. [5]). For an arbitrary operator T, { T}', { T}" and Alg T denote the commutant, double commutant and the weakly closed algebra generated by T and I, Presented to the Society, October 13, 1978; received by the editors October 24, 1978. AMS (MOS) subject classifications (1970). Primary 47A45; Secondary 47C05.

Comparison of dynamic properties of canal-evoked vestibulospinal reflexes of the neck and forelimb in the decerebrate cat.

The responses of neck and forelimb muscles to sinusoidal polarization of the horizontal canal nerve were compared by recording from these muscles simultaneously. Contrary to results on the vestibulocollic reflex, the central phase lag in the vestibulo-forelimb reflex increases with increasing frequencies up to 3 Hz. This demonstrates a difference in the organization of vestibular-driven pathways to neck and forelimb muscles.

Effect of 6-hydroxydopamine on baroreceptor-heart rate and nasopharyngeal reflexes of the rabbit.

The baroreceptor-heart rate reflex was studied in conscious rabbits by deriving sigmoid mean arterial pressure (MAP)-heart period (HP, pulse interval) curves before and at different times after intracisternal (i.c.) injection of either vehicle or 6-hydroxydopamine (6-OHDA). Each curve was characterized by the HP range (HPR) between upper and lower HP plateau levels, median blood pressure (BP50), and average gain (G) about BP50. Intracisternal vehicle was without effect on these parameters at 2 and 4 hr and on day 7 after injection. After giving 400 or 600 μg/kg 6-OHDA, there were similar significant rises at 2 and 4 hr in HPR and G to about 200% of control, and a rise in BP50 of about 10 mm Hg. In pontine (decerebrate) rabbits there were similar rises in HPR and G. but BP50. decreased. Chronic changes after 6-OHDA included a rapid weight loss necessitating artificial feeding. After 400 μg/kg weight was regained by day 7 and BP50 and threshold for eliciting bradycardia increased significantly by 13.7 $ 2.3 mm Hg. Absence of significant parameter changes after 600 μg/kg on day 7 was considered to be due to residual fluid balance disturbances in this group. These appeared to be no longer present in 6 rabbits given a second i.c. dose of 600 μg/kg on day 7 and studied 1 week later, when changes in reflex properties consisted of a rise in BP50 (10.9 $ 3.7 mm Hg), reduction in G to 52 $ 17.8% of control, a small reduction in HPR, and impairment in the cardiac sympathetic component of the HP response studied after vagal block. The nasopharyngeal reflex, consisting of a rise in HP and maintenance of MAP close to resting, was evoked by graded inhalation of formalin vapor. The responses were not significantly altered after i.c. vehicle. After 600 μg/kg 6-OHDA, MAP was significantly less well maintained at 2 and 4 hr and on day 7 than before injection, and there were also significant changes in HP response. Neither MAP nor HP responses were further impaired by a second dose of 6-OHDA on day 7. and both were virtually restored 1 week later. The results suggest that catecholaminergic neurons normally participate in the baroreceptor-heart rate reflex and the nasopharyngeal heart rate and constrictor reflexes and that different groups of neurons probably modulate each response.

Concept of Equivalence Relations and Conservation of Liquid in Preschool Children

The acquisition of logic involved in the concept of equivalence, and its relationship to attainment of conservation of liquid were studied. Equivalence was operationalized according to set theory model—as relationships characterized by three logical properties of reflexivity (R), symmetry (S), and transitivity (T). Each property was assessed by two procedures. Twenty-eight children (age range 4–0 to 5–5) were administered: (1) Pretest for relational terms, (2) Equivalence Battery, (3) Liquid Conservation Task, (4) Liquid Conservation Task—Reduced saliency condition. The three logical properties (each assessed two ways) do not develop in an invariant ordinal sequence (R S T); however, a “psychometric” order of increasing task difficulty did emerge. For all three abilities, one assessment procedure was consistently easier than the other. A significant positive relationship between age and degree of mastery of equivalence logic was found. In this study, complete mastery of equivalence was a necessary condition for attainment of conservation. The data support the proposition that saliency of perceptual change in a conservation task may be a roadblock to attainment of conservation in some preschool children, indirectly suggesting that mastery of equivalence logic probably is not a sufficient condition for conservation.

The intra-aural muscle reflex in retrocochlear pathology: a model study in the rabbit.

An animal model for the evaluation of the acoustic stapedius reflex is described. The intra-aural muscle reflex in the rabbit can be recorded with a technique identical to that used in man. The validity and reproducibility of the measurements are good. Lesions in the reflex pathway were shown to be followed by changes in reflex properties. The type of alteration depended on the location of the damage. Lesions in the dorsal cochlear nucleus were not followed by reflex changes. Lesions in the ventral cochlear nucleus and/or the eighth nerve were followed by a rise of reflex threshold and often, but not always, by reflex decay. Lesions in the midline of the trapezoid body were followed by specific changes in the crossed reflex, whereas the ipsilateral reflex was unaffected. The advantage of making simultaneous ipsilateral and contraleral reflex recordings was pointed out.

Eye movements due to linear accelerations in the rabbit.

1. Compensatory vertical or torsional eye movements of rabbits caused by linear accelerations along the transverse or sagittal axis were measured. Sinusoidal accelerations (parallel swing) in a frequency range of 0-068--1-22 Hz and acceleration steps (linear track) of 0-02--0-11 g were applied. 2. On the parallel swing, properties of the maculo-ocular reflexes were similar for transverse and sagittal acceleration. Gain (rotation of eye/rotation of the resultant linear vector) proved to be very low: about 0-1 for 0-3 Hz and smaller than 0-01 for frequencies above 1-0 Hz. The decrease in gain was accompanied by an increase in phase lag to about 180degrees. No non-linearity was revealed by the use of different amplitudes (10--30 cm). 3. On the linear track, eye deviation after an acceleration step took many seconds to develop fully. Gain increased with time and was about 0-65 after 5 sec. 4. The results indicate that the responses of the otoliths, as reflected in maculo-ocular reactions, are very slow. Fluctuations in the direction of gravity seem to be averaged over several seconds by the system. This may explain that erratic linear accelerations(frequency greater than 1 Hz) during locomotion or transport do not lead to eye movements or disorientation.

Some properties of conditioned and unconditioned eyelid reflexes in the albino rat

Eyelid responses in the rat were recorded as electromyographic activity (EMG) or as movements detected by a photoelectric technique. Spontaneous blinks, startle responses to acoustic stimuli, unconditioned responses to air puffs, and conditioned responses based on the corneal reflex were recorded under a variety of conditions. Special attention was given to topographical and temporal characteristics of the responses. Some relationships between the EMG and eyelid movements are described, as well as changes in eyelid responses related to habituation, conditioning, and various stimulus manipulations, In addition to the substantive findings, the study suggests that the rat may yet become a useful S in the study of eyelid conditioning.

Equivalence and Order Relations as Interrelated by Four- and Five-Year-Old Children

The purpose of this study was to investigate interrelationships among 4- and 5-year-old children's ability to conserve length relations not involving the asymmetric property and consequences, conserve length relations involving the asymmetric property and consequences, use the reflexive and nonreflexive properties of length relations, and use the transitive property of length relations at 2 different points in time: (1) after formal experiences only in establishing a length relation between 2 curves and (2) after selected formal experiences in (1) and in conserving length relations and the usage of properties of length relations. The conclusions of the study are: (a) an ability to conserve length relations not involving the asymmetric property and consequences precedes an ability to conserve length relations involving the asymmetric property and consequences; (b) an ability to conserve length relations involving the asymmetric property and consequences precedes an ability to use transitivity of length relations; and (c) an ability to use the reflexive and nonreflexive properties is not related to an ability to conserve length relations not involving the symmetric property and consequences, use the transitive property of length relations, or conserve length relations involving the asymmetric property and consequences.

Sexual Initiating Behaviour By Female Rhesus Monkeys (Macaca Mulatta) Under Laboratory Conditions

AbstractObservations were made on oppositely-sexed pairs of adult rhesus monkeys during 60-min tests when females were both intact (215 tests) and ovariectomized (196 tests). Three special gestures, named the hand-reach, head-duck and head-bob were described in female rhesus monkeys, and evidence is put forward that, like the well-known "presentation" gesture, they too served as female sexual invitations. They occurred most frequently immediately before and during the mounting sequence and ceased abruptly after the male's ejaculation. Although individually less effective than presentations in stimulating mounting by males, hand-reaches, head-ducks and head-bobs together initiated a larger total number of mounts: thus, they were important invitational gestures. Ovariectomy resulted in a dramatic decrease in the numbers of these sexual invitations as female receptivity declined. Hand-reaches, head-ducks and head-bobs possessed some of the stereotyped properties of reflexes and, unlike presentations, never occurred in non-sexual behavioural situations or in response to a non-sexual stimulus (e.g. male threat) ; they may thus provide a more direct indication of the female's motivational state.

Reflex Organization in the Swimmeret System of the Lobster

ABSTRACT The dynamic properties of the intrasegmental swimmeret reflexes of the lobster Homarus americanas were studied by recording the discharge of the motor neurones while the swimmeret was moved sinusoidally in its natural arc over a wide range of frequencies. The reflex responses of the excitor neurones of both powerstroke (retractor) and returnstroke (protractor) muscles display hysteresis. In both cases the efferent response corresponding to a given limb position is usually greater during imposed retraction than during protraction. The cyclic efferent reflex response follows the sinusoidal movement stimulus at movement frequencies up to and beyond those which occur naturally during swimmeret beating, with no change in the position of maximum reflex activity in the cycle. The reflexes are therefore capable of influencing the motor output on a cycle-by-cycle basis. The strength of the reflex response is maximum between 1 and 3 Hz. of imposed movement, and declines to either side of this range. The dynamic properties of the reflexes are therefore adjusted so that the maximum amplification of the rhythmic central motor command occurs at the natural frequency of swimmeret beating.

Reflexive, symmetric, and transitive properties of relations

Some contemporary ideas graphically illustrated

The Pontrjagin Duality Theorem in Linear Spaces

The Pontrjagin Duality Theorem, known to be true for locally compact groups, asserts that the given group and the character group of its character group are isomorphic under a natural mapping. So-called linear topological spaces (l.t.s.) are equivalent to their second conjugate spaces, again under a natural mapping. This raises two questions: first, for what class of topological groups does the Pontrjagin theorem hold? Second, what relation, if any, is there between the two kinds of theorem when considered in linear spaces? The present paper answers the first question in part,. bly showing that in an extensive class of infinite-dimensional (and thus not locally compact) topological linear spaces the Pontrjagin theorem is valid, and the second by showing that in reflexive linear topological spaces the group-duality theorem is also true and, in fact, merely restates the reflexive property. The key observation which makes our results possible is very simple: if f is a linear functional on a real l.t.s. then the function x defined by: x(x) = exp (if(x)) for each x in the space, is a character. The author's proof of the main theorem as presented to the Society (abstract 209t, Dec. '48) leaned heavily on Arens' paper [1].' It has since been possible to make this investigation more self-contained, and in so doing, to generalize its principal result from holding for real reflexive Banach spaces to arbitrary locally convex real l.t.s. which are either reflexive (though not necessarily either complete or normable) or Banach spaces (though not necessarily reflexive). This has served also to settle the converse problem: since completeness and normability suffice to make the Pontrjagin theorem valid it becomes clear that reflexivity is not a necessary condition for, and so certainly not identical with, the group-duality theorem, though in the special case of reflexive spaces the two sorts of duality coincide. It should be pointed out that despite the fact that Arens' results are not too obviously or heavily leaned upon in this paper in its present form, the ideas in [1] supplied the clue and motive, as well as occasionally the method for the discovery of these theorems. The author is indebted also to J. L. Kelley and to Irving Kaplansky for helpful discussions, and to the latter especially for the essential ideas in the proof of Lemma 1.

REFLEX DISCHARGE FROM THE SPINAL CORD OVER THE DORSAL ROOTS

REFLEX DISCHARGE FROM THE SPINAL CORD OVER THE DORSAL ROOTS

I. S. Makovsky. Sound reflexes during removal of the temporal regions of the cerebral hemispheres in dogs. Thesis. St. Petersburg

The author, at the suggestion of Prof. IP Pavlova, set himself the goal of studying the properties of the so-called artificial conditioned reflexes to a break in sounds. Having prefaced a brief literary sketch of the doctrine of conditioned reflexes, the author describes the methodology for studying the mentioned reflexes in four dogs. At the same time, one dog developed a sedative conditioned reflex to a break in the sound of a chromatic pipe; two dogs developed an acidic (with hydrochloric acid) conditioned reflex to the stop of the metronome sound, and the fourth dog developed a sedative conditioned reflex to the stop of the metronome sound. A conditioned reflex to a sound break was developed in such a way that minute after the sound break, which lasted 1 minutes, the dog was given either 2.0 t. economic powder (1 tsp. meat por.+2 tsp. suharnago), if she developed a sedative reflex, or poured into her 5.0 0.25% solution of HC1, if she developed an acid reflex.