Integration Of Reflexes Research Articles

Neuropeptide Y-immunoreactive perikarya and nerve terminals in the rat medulla oblongata: relationship to cytoarchitecture and catecholaminergic cell groups.

The aim of this study was to examine details of the distribution of neuropeptide Y (NPY)-immunoreactive perikarya and nerve terminals in the medulla oblongata in relation to cytoarchitectonically and functionally distinct catecholaminergic regions. The immunoperoxidase method was combined with Nissl staining to determine nuclear boundaries of transmitter-identified nerve cell bodies and to examine the relationship between populations of NPY-immunoreactive neurons and catecholaminergic cell groups (A1, A2, C1, C2, and C3) in serial sections. Previous studies using immunofluorescence have described the existence of NPY catecholaminergic immunoreactive nerve cell bodies in the brainstem. No information is currently available with regard to details of the distribution of these peptidergic neurons and nerve terminals in the functional subnuclear units of the medulla oblongata. In this study we have delineated the anatomical association of NPY immunoreactivity with cardiovascular function. Neuropeptide Y-immunoreactive neurons were found located in close association with noradrenergic neurons of the A1 cell group in the caudal ventrolateral medulla oblongata, where they were usually found located dorsal to the lateral reticular nucleus (LRt). A second population of NPY-immunoreactive neurons was found located medial to the A1 cell group in the ventral subdivision of the reticular nucleus of the medulla (MdV). Neuropeptide Y-immunoreactive neurons in the rostral medulla were found located in regions corresponding to the principal distribution of adrenergic neurons in the C1, C2, and C3 cell groups. In the dorsomedial medulla (A2 region) NPY-immunoreactive neurons were localized in the area postrema (ap) and in a number of subnuclei of the nucleus of the tractus solitarius (nTS), i.e., the dorsal parasolitary region (dPSR), the dorsal strip (ds), the periventricular region (PVR), and the ventral parasolitary region (vPSR). The location of NPY-immunoreactive perikarya and nerve terminals in the dorsal subnuclei of the nTS, i.e., the dPSR and ds, is of particular significance, since this distribution corresponds with the location of small adrenergic neurons as well as with the site of termination of aortic and carotid sinus nerve afferent fibers. NPY-immunoreactive neurons in the dorsomedial medulla are ideally situated for receiving monosynaptic input from baroreceptor afferents and could play a key role in the central integration of cardiovascular reflexes.

Functional identification of the central projections of afferent renal nerves.

The central integration of cardiovascular reflexes produced by activation of renal sensory mechanisms was examined by studying arterial pressure and regional blood flow responses to electrical stimulation of the renal afferent nerves. Spinal transection, rostral to the entry into the cord of renal afferent projections, abolished the cardiovascular response consisting of an a fall in arterial pressure, mesenteric vasoconstriction and vasodilation in the hindquarters. Several supraspinal structures at medullary, midbrain and forebrain levels were identified by lesion studies to be important for the reflex responses. Lesion of NTS abolished the hindquarter vasodilator response but left the mesenteric vasoconstrictor response intact. Lesions of the parabrachial complex produce similar effects whereas lesions in the periventricular preoptic region of hypothalamus abolished mesenteric vasoconstriction and left hindquarter vasodilation unaffected. These studies demonstrate that cardiovascular reflexes elicited by activation of renal sensory nerves require integrity of spinal pathways and are differentially integrated at several levels of the neuraxis.

A light and electron microscopic analysis of the sacral parasympathetic nucleus after labelling primary afferent and efferent elements with HRP.

Primary afferent input to the cat sacral parasympathetic nucleus (SPN) has been examined by injury filling sacral dorsal roots, ventral roots, or both with horseradish peroxidase (HRP). Appropriate spinal segments were processed for the demonstration of HRP with diaminobenzidine and prepared for sequential light (LM) and electron (EM) microscopy. At the LM level, a large fascicle of primary afferent fibers was observed passing ventrally along the lateral edge of the dorsal horn into the region of the SPN. Varicosities were seen throughout the course of the axons but were particularly abundant within the SPN. Injury filling of the ventral roots with HRP resulted in a Golgi-like labelling of preganglionic neurons and their dendritic arbors, as well as ventral root afferent fibers. Swellings on both dorsal and ventral root afferent axons were observed in close apposition to labelled preganglionic neurons and their dendrites. At the ultrastructural level, afferent terminals were found to contain clear spherical vesicles; 66% of these terminals also contained at least one dense-cored vesicle. Of particular interest was the presence of labelled dorsal and ventral root afferent terminals synapsing on labelled preganglionic neurons. Preganglionic neurons were also postsynaptic to unlabelled terminals containing clear spherical (79.7%) or pleomorphic vesicles (20.3%). These data indicate that preganglionic neurons receive direct input from several sources, and provide the first demonstration of direct input to these cells from sensory fibers in the dorsal and ventral roots. The connections described in the present study provide interesting and, as yet, unexplored possibilities for sensory and autonomic reflex integration.

Central projections of afferent renal fibers in the rat: an anterograde transport study of horseradish peroxidase

The projections of afferent renal fibers (ARN) to dorsal root ganglia and into the spinal cord of the rat were studied using the anterograde transport of horseradish peroxidase (HRP). Crystalline HRP was applied to the proximal cut ends of renal nerves or injected as a concentrated solution into the kidney, on either the right or left side. After a survival time of 40–120 h, sections of thoraco-lumbar dorsal root ganglia (DRG) and spinal cord were cut and processed according to the tetramethyl benzidine method. HRP applied either to the ARN or to the kidney on the left labeled neurons in the DRG from T8 to L2. On the other hand, HRP application on the right side resulted in labeling of neurons in DRG T6 to T13. No labeled neurons were found in the contralateral DRG. Labeled neurons in the DRG were of the small (11–20 μm) and medium (30–42 μm) size and were distributed in all portions of the DRG. In the spinal cord the greatest concentration of labeled ARN from the left were found in segments T10-L1, whereas projections from the right ARN were concentrated primarily in segments T7-T10. Labeled fibers entered along the medial aspect of the ipsilateral dorsal horn and projected both rostrally and caudally in the medial portion of Lissauer's tract, sending some collaterals into lamina I. The majority of labeled fibers coursed ventrally along the medial aspect of the dorsal horn towards the midline where they terminated in the region of the dorsal gray commissure, just dorsal to the central canal. Additionally, labeled fibers from the medial projection passed into laminae III-V. No labeled fibers or terminals were observed in the contralateral spinal cord. These data show that ARN enter the spinal cord through several DRG and provide the first anatomical demonstration of central sites of termination of ARN. These spinal sites of projection of sensory information from the kidney are likely to be central sites of integration of reno-renal and visceral reflexes.

Ayres' Clinical Observations: Performance of Four and Five Year Old Children

Data was gathered on 41 children aged four and five years, using the Ayres' clinical observations form. Significant differences were found between the two age groups on items measuring co‐ordination, co‐contraction, maintenance of anti‐gravity postures, reflex integration and standing balance. Four year old children in particular, had difficulty assuming the prone extension, supine flexion, asymmetrical tonic neck reflex (ATNR) inhibiting posture, and standing balance positions and the use of these items with four year old children was questioned. The results also suggested that the present qualitative scoring may not be suitable for both these age groups and could be modified according to the quantitative scores reported in this article. Further work is needed to extend these age norms using a wider population, and to provide further reliability and validity data.

Developmental implications of clinically applied vestibular stimulation.

Recent research has promoted the development of several techniques that use various forms of sensory stimulation to improve the neuromotor development of high-risk infants and developmentally delayed children. One of the newest and most popular adjuncts to therapy for developmentally delayed children is vestibular stimulation. The applied clinical research using vestibular stimulation activities with healthy human infants, infants at risk, and young children with developmental delay disorders is reviewed. The literature discussed indicates that controlled vestibular stimulation has had positive effects on arousal level, visual exploratory behavior, motor development, and reflex integration. Also discussed is the need for continued applied clinical research to further substantiate the most effective type of vestibular stimulation and the population for which such stimulation is most beneficial.

Motor proficiency in children with psychosis.

Twenty-one children, aged 8 to 11 years, whose disorders were diagnosed as childhood psychosis, were tested by using the Bruininks-Oseretsky Test of Motor Proficiency. In addition, two reflex tests, one righting reaction, and a test for muscle tone were administered. The children showed large variations in all motor skill scores, which ranged from average to far below average. Total test battery scores indicated all children but one scored at or below the first percentile of the standardized sample. Delayed reflex integration and delayed mature righting reactions were observed and in some cases were associated with low motor test scores. Hypotonicity was observed in 12 of the 21 children. Results indicate that for children with psychoses, early intervention is important and carefully planned motor and reflex integration programs should be applied.

Psychometric Analysis of the Test of Sensory Integration

A 36-item test entitled the Test of Sensory Integration was developed to measure sensory integrative functions in preschool children. It focused specifically on postural control, bilateral motor integration, and reflex integration. This version of the test is the product of two previous psychometric studies and extensive revisions over a period of four years. Data were gathered on 101 normal and 38 developmentally delayed children from three to five years of age. The psychometric quality of the test was investigated in terms of domains validity, construct validity, interobserver reliability, decision reliability, and retest stability. The findings were that: (1) the items validly measure the domain of sensory integrative functions, (2) the total test scores can be used reliably and validly for screening decision, and (3) the postural control and bilateral motor integration subtests can be used reliably and validly for diagnostic decisions. The reflex integration subtest should be used with caution because...

Structural studies on the connectivity of the inferior mesenteric ganglion of the guinea pig

After injection of horseradish peroxidase (HRP) into the inferior mesenteric ganglion (IMG) of the guinea pig, labeled cell bodies were found in the solar plexus ganglia, the ganglia of the pelvic plexus and in the nodose ganglia as well as in the spinal cord and dorsal root ganglia at the T 3-L 4 levels. By using the fluorescent tracer True blue, labeled cell bodies could also be detected in the myenteric and submucosa ganglia of the distal colon. Application and uptake of HRP by the colonic nerves resulted in labeling of cell bodies in the dorsal root ganglia, the IMG and in the solar plexus ganglion complex indicating that the latter neurons send their axons in the intermesenteric nerve through the IMG to continue in the colonic nerves to the distal colon. When HRP was applied and diffused into the hypogastric nerves labeled cell bodies were seen in the IMG, the dorsal root ganglia and in the preganglionic nuclei of the lumbar spinal cord with 50% of the labeled neurons located dorsal and dorsolateral to the central canal. The finding of such a diversity in the nerve supply to the IMG, supports the view that the ganglion plays an important role in the integration of visceral reflexes.

The identification of specific brain nuclei in which catecholamine turnover is increased by left ventricular receptors during acute myocardial infarction in the rat

Central catecholaminergic nerves have been shown to participate in the integration of cardio-cardiac reflexes induced by coronary artery ligation in the rat. In this study we measured the turnover of dopamine, norepinephrine and epinephrine in microdissected brain regions to identify some of the specific neural loci involved in this integration. Three groups of rats, treated with α-methyltyrosine, an inhibitor of catecholamine biosynthesis were examined: left coronary artery ligation, left coronary artery ligation with the left ventricle painted with lidocaine, and sham operation. An untreated group of resting rats was also examined. Dopamine, norepinephrine and epinephrine turnover was increased in ligated rats in nucleus tractus solitarius (right and left), nucleus commissuralis, A 1-region, locus coeruleus, nucleus cuneatus, and area postrema in the pons-medulla and nucleus dorsomedialis in the hypothalamus. Norepinephrine and dopamine (but not epinephrine) turnover was increased in nucleus ambiguus in the brain stem and nucleus paraventricularis in the hypothalamus. A ligation-induced increase in norepinephrine turnover, alone, was exhibited by the A 2-region and nucleus gigantocellularis in the medulla and nucleus supraopticus and nucleus hypothalamicus posterior in the hypothalamus. Dopaminergic nerves to the nucleus gigantocellularis appeared to be inhibited following coronary ligation. The catecholamine stores of 11 nuclear regions were not influenced by coronary artery occlusion. Topical lidocaine, applied to the ischemic left ventricle, only, of ligated rats, completely restored regional brain catecholamine turnover to that found in sham-operated animals. In conclusion, we have identified discrete loci in the brain in which catecholamine turnover (as measured by α-methyltyrosine induced disappearance) is increased by the stimulation of left ventricular receptors during acute myocardial ischemia in the rat.

The Effects of a Clinically Applied Program of Vestibular Stimulation on the Neuromotor Performance of Children with Severe Developmental Disability

The effect of a program of controlled vestibular stimulation on the gross motor, and relax development of 38 severely and profoundly retarded, nonambulatory, developmentally delayed children were investigated employing a pretest/posttest control group design. Data analysis revealed that subjects receiving a combined program of sensor motor therapy and controlled vestibular stimulation make significantly greater gains on measures of reflex integration, gross motor, and fine motor development than control subjects receiving a progression of normal motor development and appeared to be related to the age of subjects and to the presence or absence of identifiable neuromotor spasticity.

A learning disability screening program in a public school.

The outline of screening program for learning disabilities in a public school is presented in this paper. The screening program consisted of four standardized measures (Information Subtest of the WPPSI, SEARCH, Evanston Early Identification Scale, Bender-Gestalt) and six of the clinical observations suggested by Ayres. Forty-three kindergarten and first graders (25 males, 18 females) were tested and each child was categorized as low, moderate, or high risk for learning disabilities on each of the measures. Approximately 10 percent of the children were identified as at high risk for learning disabilities, but the children did not perform at the same risk level on all measures. A factor analysis of the four measures and six observations revealed that three factors prevailed in this screening program; cognitive abilities, fine motor control, and reflex integration. This analysis also indicated the importance of assessing neurophysiological immaturity in a screening program. The implications of the categories used are discussed.

The Effects of a Clinically Applied Program of Vestibular Stimulation on the Neuromotor Performance of Children with Severe Developmental Disability

The effect of a program of controlled vestibular stimulation on the gross motor, and relax development of 38 severely and profoundly retarded, nonambulatory, developmentally delayed children were investigated employing a pretest/posttest control group design. Data analysis revealed that subjects receiving a combined program of sensor motor therapy and controlled vestibular stimulation make significantly greater gains on measures of reflex integration, gross motor, and fine motor development than control subjects receiving a progression of normal motor development and appeared to be related to the age of subjects and to the presence or absence of identifiable neuromotor spasticity.

The measurement of vestibular-based functions in pre-school children.

Abstract A 21-item test entitled Assessment of Sensorimotor Integration in Pre-School Children (1) was developed to measure vestibular-based functions in pre-school children. It focuses on postural control, reflex integration, and bilateral motor integration. Data were gathered on 113 normal and 23 developmentally delayed children from three to five years of age. The psychometric quality of the test was investigated in terms of domain validity, discriminant validity, and interobserver reliability. It was found that 1. the items validly measure the domain of vestibular-based functions, 2. the six component subtests provide strong discriminative power and a high degree of accuracy for classifying children as normal and delayed, and 3. the test could be administered with a high degree of objectivity by therapists with little or no experience in sensory integrative testing. These findings should be regarded as tentative until cross-validation studies and research on construct validity and decision-making reliability have been conducted.

Vestibular Stimulator for Handicapped Clients

Vestibular stimulation is used in the treatment of handicapped clients to improve gross motor skills and to facilitate reflex integration.1 Research indicates that the vestibular system has a strong influence on muscle tone.2 Clients with abnormal muscle tone often cannot stay safely on scooter boards or other equipment used for stimulating the vestibular system. Although small children can be held and moved around by the therapist to provide this input, this is difficult to do with larger children and young adults. We built a round scooter board with uprights and a rim to use in providing vestibular stimulation for our larger moderately and severely involved clients (Fig. 1). A ¾-inch plywood base, 26 inches in diameter, is reinforced underneath by perpendicular boards, using a crosslap joint. Four 2-inch platform casters are mounted on these boards.…

Integration of reflex responses in the control of blood pressure and vascular resistance

This overview presents four important concepts related to integration of cardiovascular reflexes. 1. 1. Activation of sympathetic efferent activity to various organs is nonuniform. Simultaneous activation of both sympathetic and parasympathetic efferent pathways may occur. These effects are evident in the responses to diving and stimulation of chemoreceptors. Both diving and stimulation of chemoreceptors decrease heart rate and myocardial oxygen demand and cause intense peripheral vasoconstriction, which limits oxygen delivery to the periphery. Stimulation of chemoreceptors also causes active coronary vasodilatation favoring an optimal distribution of blood flow to the heart. 2. 2. When two groups of sensory afferents that cause opposing responses are activated simultaneously, the effect of one sensory afferent system will override the other. During hypotension caused by occlusion of the circumflex coronary artery, the reflexes originating in cardiac vagal afferents are inhibitory and reverse the effect of unloading of arterial baroreceptors. The net effect is not simply blockade of sympathetic vasoconstrictor effects, but withdrawal of sympathetic tone. Thus, the cardiac “reflex” overrides the effects of arterial hypotension. 3. 3. The reflex response to activation of one group of sensory afferents may be dependent on the input from other groups of afferents to the medullary neurons. At low carotid sinus pressure, the “gains” of the chemoreceptor and somatic reflexes are augmented. The cardiopulmonary vagal afferents modulate the arterial baroreceptor reflex as well as the chemoreceptor and somatic reflexes. The cardiopulmonary vagal afferents, when activated, suppress the sympathetic excitatory response to arterial hypotension, to chemoreceptor stimulation and to somatic afferent stimulation. Another important interaction is that of the thermal receptors which, when activated by heat, suppress the vasoconstrictor response to arterial hypotension in cutaneous more than in muscular beds. 4. 4. Stimulation of sensory afferent receptors may be modified by drugs or humoral factors acting on the receptor itself or on the chemical and mechanical characteristics of the tissues surrounding the receptor. Acetylstrophanthidin injected into the circumflex coronary artery potentiates the sympathetic inhibitory response to activation of cardiac sensory afferents (vagal afferents) by volume loading and by occlusion of the circumflex. The sensitization may explain in part the action digitalis has on the peripheral circulation in heart failure. The clinical implications of these four important physiologic concepts are discussed.

Effect of sensory integrative therapy on the neurometer development of retarded children.

Three groups of trainable mentally retarded children participated in three different motor programs for an eight-month period. Children receiving sensory integrative therapy showed the greatest gains on test batteries for reflex integration and gross and fine motor skills. Children in a developmental physical education program demonstrated greater improvement on the same test batteries than a third group of children who participated in a recreational, adaptive physical education program and an "arts and crafts" oriented therapy program. Results of data analysis indicate that neuromotor development may be enhanced more effectively by activities which facilitate improved postural responses rather than by practice of specific motor skills.

Central cholinergic interactions in somato-vegetative reflexes

In cats lightly anaesthetized with urethane (600 mg/kg, i.p.), electrical stimulation of the sciatic nerve elicited frequency-dependent pressor reflexes and contractions of the nictitating membrane. Administration of oxotremorine (0.2 mg/kg, i.v.) or physostigmine (0.5 mg/kg, i.p.) resulted in depression of the pressor reflexes. At the same time, physostigmine enhanced the reflex contractions of the nictitating membrane, while oxotremorine induced sustained contraction of the latter. All these effects were antagonized by the tertiary amine scopolamine, but not by the quaternary atropine methylbromi. The results point to a role of central cholinergic mechanisms in the integration of somato-vegetative reflexes, and give evidence that the sympathetic driving of different effectors is not uniformly organized by the central nervous system.

Central neural integration of baroreceptor reflexes: Their interaction with central and peripheral catecholamines and role in neurogenic hypertension

Central neural integration of baroreceptor reflexes: Their interaction with central and peripheral catecholamines and role in neurogenic hypertension

Tension receptor reflexes in the walking legs of the crab Cancer pagurus.

THE decapod crustaceans have many advantages for the study of the neuronal mechanisms controlling simple behaviour1–3. Numerous authors have investigated the functions of the walking legs, but models of the control mechanisms have been presented in terms of central programmes and reflexes related simply to the positions and movements of the joints4,5; little attention has been paid to the control of tension in the chief working muscles. It has been shown, however, that the tension of some of these muscles is monitored by sense organs6. We present here some initial findings on the reflexes produced by input from these tension receptors and the integration of such reflexes in the intact animal.