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PubMed1971

Effects of descending impulses on transmission through the spinocervical tract.

1. Micro-electrode recordings were made from ascending axons of the spinocervical tract in unanaesthetized decerebrate cats before, during and after reversible cold block of impulse conduction in the spinal cord rostral to the recording site.2. Most units (forty-one of forty-four) fell into one of four categories as defined by their evoked responses to mechanical stimulation of identified cutaneous receptors. These categories were; Type I excited by movement of tylotrichs (hairs) in the decerebrate preparation but by movement of all types of hairs after block of descending impulses; Type II excited by movement of guard hairs and usually weakly by pressure in the decerebrate state but by movement of all types of hairs and by pressure in the spinal state; Type III excited by movement of all types of hairs and often by pressure in the decerebrate animal but by movement of all types of hairs and always by pressure in the spinal animal; Type IV weakly excited by heavy pressure or with no receptive field in the decerebrate state but excited by pressure in the spinal state.3. The descending influences depressed the spontaneous activity and the evoked responses to harmful stimuli.4. The descending influences depressed inhibitory inputs from segmental levels.5. The functional significance of the descending control is discussed.

Action Potentials↗
PubMed2006

Fast amplification of dynamic synaptic inputs in spinal motoneurons in vivo.

The ability of voltage-dependent inward currents (likely Na(+)) of the adult cat lumbar motoneurons to amplify rapidly changing (i.e., dynamic) synaptic inputs was investigated using in vivo intracellular recording techniques. Fast amplification was assessed by measuring the magnitude of the high-frequency (180 Hz) component of the Ia synaptic input due to tendon vibration as a function of somatic voltage and was compared with the previously observed amplification of steady inputs (steady state response of PICs to slow inputs). Data from 17 experiments show that amplification of the dynamic input indeed occurred and was directly linked to neuromodulatory drive (standard state: decerebrate with intact descending neuromodulatory systems vs. minimal state: pentobarbital with said systems significantly inhibited). Fast amplification factors averaged 2.0 +/- 0.7 (mean +/- SD) in the standard neuromodulatory state. That is, the effective synaptic current was nearly twice as large at its peak as it was at hyperpolarized levels, ranging as high as 2.6. Although fast amplification was often smaller than the amplification of steady inputs, the difference was not statistically significant. However, the voltage at which fast amplification began was approximately 10 mV more depolarized (P < 0.01). It is concluded that both dynamic and steady inputs can be amplified, but there may be differences in mechanism.

Achilles Tendon↗
PubMed1976

Effects of morphine upon the lamina V type cells activities in the dorsal horn of the decerebrate cat.

The effects of morphine (2 mg/kg i.v.) upon the transmission of nociceptive messages at the spinal level have investigated in decerebrate cats by studying its effects on the activities of lamina V dorsal horn interneurons. In contrast to previous results obtained on the spinal cat, morphine had little or no effects on lamina V type cells in the decerebrate preparation. The mean values for spontaneous activity and responses to natural noxious stimulation were practically identical before and after morphine administration. Moreover, no significant depressive effect was found on responses induced by supramaximal transcutaneous stimulation. However, for this type of activity a depressive effect was revealed, if only the late component of units which presented bimodal responses were considered. We were unable to demonstrate after morphine administration an increase of the descending inhibitory effects induced on lamina V cells by stimulation of the central inferior nucleus of the raphe. Additional experiments using reversible spinalization (by cooling the cord at the thoracic level) suggest that the lack of effect of morphine on decerebrate animals could be explained by the fact that in this preparation, descending inhibitory influences are strongly exacerbated and thus may mask the depressive effects of this drug. These results indicate that the direct electrophysiological evidence of an increase of the descending control systems after morphine administration must be performed in the intact preparation in order to avoid the effects ot their exacerbation in the decerebrate state.

Action Potentials↗
PubMed1983

Differential decerebrate control of depolarization in the central terminals of cutaneous afferents in the sacral cord.

Presynaptic depolarization of cutaneous afferents has been investigated in the sacral cord of decerebrate cats before and after spinal cord transection. In the decerebrate state the central terminals of caudal femoral cutaneous nerve are depolarized by ipsilateral volleys entering the cord via sacral and lumbar dorsal roots. A significant increase of depolarization occurring after severing the cord indicates that there is tonic decerebrate inhibition of presynaptic depolarization in terminals of caudal femoral cutaneous nerve. In contrast to this finding, presynaptic depolarization evoked in the central terminals of the pudendal nerve by ipsilateral volleys entering the cord through sacral and lumbar dorsal roots is not subjected to decerebrate inhibitory control. It is suggested that differential inhibitory control of depolarization in the central terminals of cutaneous nerves in the sacral cord is related to the intraspinal course of their fibres, to differences in the receptor types involved, and to the location of their innervation fields. In more than half of the decerebrate preparations stimulation of the central terminals of cutaneous afferents through microelectrodes evokes antidromic spikes appearing simultaneously in ipsi- and contralateral nerves. The time course of bilateral excitability changes is similar on both sides of the cord. It is assumed that presynaptic effects are transmitted to the contralateral side by collaterals of ipsilateral cutaneous afferents.

Afferent Pathways↗
PubMed1984

The effects of small doses of barbiturate on the activity of primate nociceptive tract cells.

The activity of neurons identified as or similar to spinothalamic tract cells was compared in anesthetized, intact monkeys and in unanesthetized, decerebrate or spinalized animals. Background activity and responses to A- and C-fiber volleys were smaller in decerebrate than in the other preparations, suggesting the presence of a tonic descending inhibition of nociceptive tract cells in the decerebrate state. Injections of small doses of sodium pentobarbital caused a slight increase in sensitivity of peripheral receptive fields to mechanical stimuli in some cells, and an increase in responses to squeezing the skin with forceps and to C-fiber volleys. Larger doses of pentobarbital reduced the responses to A- and C-fiber volleys. These observations suggest that the activity of nociceptive tract cells is well preserved in the presence of the doses of pentobarbital we routinely use and are consistent with the hyperalgesic state reported to be produced by small doses of barbiturate.

Anesthesia, General↗
PubMed1999

Receptor mechanisms underlying heterogenic reflexes among the triceps surae muscles of the cat.

The soleus (S), medial gastrocnemius (MG), and lateral gastrocnemius (LG) muscles of the cat are interlinked by rapid spinal reflex pathways. In the decerebrate state, these heterogenic reflexes are either excitatory and length dependent or inhibitory and force dependent. Mechanographic analysis was used to obtain additional evidence that the muscle spindle primary ending and the Golgi tendon organ provide the major contributions to these reflexes, respectively. The tendons of the triceps surae muscles were separated and connected to independent force transducers and servo-controlled torque motors in unanesthetized, decerebrate cats. The muscles were activated as a group using crossed-extension reflexes. Electrical stimulation of the caudal cutaneous sural nerve was used to provide a particularly strong activation of MG and decouple the forces of the triceps surae muscles. During either form of activation, the muscles were stretched either individually or in various combinations to determine the strength and characteristics of autogenic and heterogenic feedback. The corresponding force responses, including both active and passive components, were measured during the changing background tension. During activation of the entire group, the excitatory, heterogenic feedback linking the three muscles was found to be strongest onto LG and weakest onto MG, in agreement with previous results concerning the strengths of heteronymous Ia excitatory postsynaptic potentials among the triceps surae muscles. The inhibition, which is known to affect only the soleus muscle, was dependent on active contractile force and was detected essentially as rapidly as length dependent excitation. The inhibition outlasted the excitation and was blocked by intravenous strychnine. These results indicate that the excitatory and inhibitory effects are dominated by feedback from primary spindle receptors and Golgi tendon organs. The interactions between these two feedback pathways potentially can influence both the mechanical coupling between ankle and knee.

Animals↗
PubMed1980

Hypotensive brain stem necrosis or cardiac arrest encephalopathy?

Selective symmetrical necroses of many tegmental brain stem nuclei including motor cranial nerve nuclei, superior and inferior colliculi, cuneate and gracilis nuclei, and others are known as hypotensive brain stem necrosis (Gilles 1969). We found such lesions in eight infants and seven adults. Examination of their clinical records revealed a well documented episode of cardiac arrest in each case. Cardiac output was restored in all but one patient 5 min to 4 h after the beginning of resuscitation. All patients remained comatose in a decerebrate state up to their death 17 h to 4 weeks after admission. Our findings and a review of the literature indicate that this type of lesion relates specifically to cardiac arrest. The term "hypotensive brain stem necrosis"is a misnomer and should be replaced by the term "cardiac arrest encephalopathy".

Adolescent↗
PubMed1988

Maintained changes in motoneuronal excitability by short-lasting synaptic inputs in the decerebrate cat.

1. During investigation of the tonic stretch reflex in the unanaesthetized decerebrate cat we observed that a short train of impulses in Ia afferents from the soleus muscle (or its synergists) may cause a prolonged activity in the soleus muscle as judged by EMG and tension recordings. This excitability increase, which outlasted the stimulus train, could stay virtually constant during long periods (even minutes), but could be terminated at any time by a train of impulses in, for example, the peroneal nerve. 2. Gradation of the strength of stimulation and the duration of the train of impulses show that the amount of maintained excitability increase depends-within some limits-on the total amount of Ia impulses. 3. In paralysed preparations a short train of impulses in Ia afferents from any part of the triceps surae, caused a maintained increase of the efferent activity in the nerves to triceps surae and a maintained increase of the triceps surae monosynaptic test reflex. These experiments demonstrate the existence of a central mechanism (in the spinal cord and/or the brain stem), which is responsible for the maintained excitability increase seen in motoneurones to the homonymous and synergic muscles. 4. In acute spinal preparations it was not possible to demonstrate any long-lasting excitability increase by a train of Ia impulses. Following intravenous administration of the serotonin precursor 5-hydroxytryptophan, mimicking the tonic activity of these pathways in the decerebrate state, it was again possible to elicit the long-lasting excitability increase by a train of impulses in Ia afferents. A subsequent I.V. injection of methysergide (a serotonin receptor blocker) abolished the long-lasting excitability increase. This set of experiments demonstrates that the basic mechanism responsible for the maintained excitability increase is located at segmental level, and involves serotonergic systems. 5. It was demonstrated that activation of several ipsilateral and crossed reflex pathways by trains of impulses in cutaneous or high-threshold muscle afferents could trigger a maintained excitability increase of those motoneurone pools which were activated by the stimulation. Trains of stimuli to facilitatory regions in the brain stem could also cause a long-lasting excitability increase of motoneurones. Furthermore, activation of all reflex pathways which mediate postsynaptic inhibition to a motor nucleus (including recurrent inhibition via Renshaw cells) could terminate the prolonged excitability increase of that particular motor nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

5-Hydroxytryptophan↗
PubMed1995

Spatial coordination by descending vestibular signals. 1. Reflex excitation of neck muscles in alert and decerebrate cats.

Electromyographic activity of dorsal neck muscles and neck torques was recorded to study vestibulocollic, cervicocollic, and combined reflexes in alert and decerebrate cats during rotations of the whole body, the body except for the head, and the head but not the rest of the body. Cats were rotated about many axes that lay in the frontal, sagittal, and horizontal planes using sinusoidal 0.25-Hz waveforms or sum-of-sinusoid wave-forms. Robust electromyographic responses were recorded from six muscles, with response directionality that in most cases did not show strong dependence on the reflex tested or on other factors including exact neck angle, stimulus amplitude from 5 degrees to 60 degrees, and intact versus decerebrate state. Based on the strength of responses to rotations about all the tested axes, neck muscles could be characterized by maximal activation direction vectors representing the axis and direction of rotation in three-dimensional space that was most excitatory during reflex responses. Responses to rotations about axes that lay in a coordinate plane were predicted by a cosine function of the angle between the axis under test and the maximally excitatory axis in the plane. All muscles were excited by the nose down phase of pitch rotation and by yaw and roll away from the side on which the muscle lay. Biventer cervicis was best activated by rotations with axes near nose-down pitch, and its axis of maximal activation also had small, approximately equal components of yaw and roll toward the contralateral side. Complexus was best excited by rotations with axes nearest roll, but with large components along all three axes. Occipitoscapularis was best excited by rotations about axes near pitch, but with a moderately large contralateral yaw component and a smaller but significant contralateral roll component. Splenius was best excited by rotations with a large component of contralateral yaw, considerable nose-down pitch, and a smaller component of contralateral roll. Rectus major was best excited by rotations near nose-down pitch, but with a substantial contralateral yaw component and smaller contralateral roll component. Obliquus inferior was best excited by rotations with a large component of contralateral yaw, but with considerable contralateral roll and nose-down pitch components. All muscles responded as though they received convergent input from all three semicircular canals. Vestibulocollic and combined reflex responses in alert cats and vestibulocollic, cervicocollic, and combined responses in decerebrate cats appeared to have the same directionality, as evidenced by insignificant shifts in maximal activation vectors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1972

Properties and distribution of peripherally evoked presynaptic hyperpolarization in cat lumbar spinal cord.

1. The action of peripheral nerve volleys on the polarization of presynaptic terminals of inactive sensory fibres in cat lumbar spinal cord has been investigated by recording (a) the dorsal root potential (DRP), (b) intracellular changes in polarization of single preterminal axons (PAD or PAH), and (c) changes in excitability of populations of preterminal axons.2. Presynaptic hyperpolarization (positive DRP-PAH) can be evoked by stimulation of muscle group III afferents as well as by volleys in cutaneous Abeta, Adelta and C afferents. These volleys can also produce presynaptic depolarization (negative DRP-PAD).3. The positive DRP is observed in the decerebrate state and increases in amplitude following spinalization.4. Picrotoxin blocks the positive DRP at the same dosages required to block the negative DRP. Test negative DRPs are depressed during a conditioning positive DRP. These results are used to support earlier suggestions that the positive DRP results from inhibition of interneurones mediating the negative DRP.5. Trains of group III stimuli at 20/sec evoke a steady positive DRP. Trains of the same intensity at 200/sec evoke a phasic negative DRP. This frequency dependence is observed for PAD and PAH in single sensory axons.6. The DRPs recorded from different dorsal root filaments in response to a given stimulus vary widely in the ratio of negative to positive DRP.7. Intracellular recording from single axons reveals that the same stimuli evoke widely varying ratios of PAD and PAH.8. Stimulation of FRA evokes PAH > PAD in PBST group I afferents, PAD > PAH in sural A fibres and intermediate effects in G-S group I units.9. It is suggested that activation of flexor reflex afferents may selectively potentiate the synaptic efficacy of large muscle afferents mediating the flexor reflex rather than large skin afferents or large afferents from extensor muscles.

Animals↗
PubMed2003

Discharge patterns of preganglionic neurones with axons in a cardiac vagal branch in the rat.

The fibre types that run in a vagal branch projecting to the rat heart are described in this study. In order to obtain spontaneous discharge in this vagal branch and optimal recording conditions, we compared the decerebrate state to urethane, urethane-chloralose and pentobarbital-chloralose anaesthesia with regard to level of chronotropic cardiac vagal tone. Administration of atropine (2 mg kg(-1), I.V.) significantly decreased baseline cardiac interval only in the decerebrate and urethane-anaesthetised rat (by 0.018 +/- 0.001 s and 0.019 +/- 0.002 s, respectively). As a result of these experiments, urethane was chosen as the anaesthetic for all subsequent studies. Using a heart rate signal-averaging method we demonstrated that rat cardiac vagal preganglionic neurones innervating the sinoatrial node should have an expiratory discharge pattern, as reported in other species. However, only 5 % of chronotropic vagal tone was found to be subject to respiratory sinus arrhythmia. A suction microelectrode method, combined with spike-triggered averaging, was employed to record activity from a total of 58 vagal afferents that had axons in this branch. Approximately 75 % of these latter sensory fibres displayed cardiac rhythm. In a separate study we also recorded 318 preganglionic neurones with axons in the right cardiac vagal branch of the rat. Respiratory-modulated preganglionic units were statistically less common than tonically firing units. Six preganglionic subtypes were categorised according to conduction velocity and respiratory discharge pattern. Myelinated B-fibre and unmyelinated C-fibre types were found to be equally prevalent and equally likely to be reflexly excited during the pulmonary chemoreflex and the peripheral arterial chemoreflexes. The electrophysiological analysis has shown how diverse the discharge patterns of the preganglionic neurones or interneurones are whose axons course in the right cardiac vagal branch of the rat. The results of these experiments demonstrate the usefulness of combining spike discrimination with multiple spike-triggered averaging to simultaneously record B and C centrifugal vagal efferents.

Action Potentials↗
PubMed1981

Chronic encephalitis in X-linked agammaglobulinaemia.

Clinicopathological and immunological findings are reported in a boy with X linked agammaglobulinaemia (XLA), who after multiple episodes of purulent infections in various organs developed encephalitis associated with excemata and non suppurative arthritis. Inspite of gammaglobulin administration he developed progressive spastic tetraparesis, convulsions, mental deterioration and blindness and died in a decerebrate state at the age of 8 years. Necropsy revealed a general diminuition of the lymphoid tissue. The atrophic brain showed multiple cystic destructions and chronic, but still active polioencephalitis with prominent inflammatory involvement of basal ganglia and brain stem. Symmetric Wernicke-like lesions were seen in inferior corpora quadrigemina. The aetiology of this particular type of chronic progressive encephalitis in XLA is unknown but some kind of viral infection is to be considered.

Agammaglobulinemia↗
PubMed1977

Long-term results in 62 cases of post-traumatic complete apallic syndrome.

After the transition state of decerebrate coma, at least four different kinds of the so-called apallic status can be identified: 1. Complete apallic syndrome: coma vigil, alertness without any awareness, mass movements only, impairment of sleep rhythm, absence of any emotional responses, postural abnormalities, some primitive motor responses, tetraplegia, and alteration of muscle tone. 2. Incomplete apallic syndrome: some of the features of the complete apallic syndrome are lacking, and the patient shows emotional reactions with appropriate grimacing and some appropriate motor responses. 3. False apallic syndrome: most signs of complete apallic syndrome are present, but the patient is in touch with the environment. This condition is somewhat similar to the so-called locked-in syndrome. 4. Functional apallic syndrome: full clinical picture of the complete apallic syndrome but full recovery within a few days. Long-term results in 62 patients, aged between 4 and 62, affected by a post-traumatic complete apallic syndrome are reported. Thirty two patients were operated upon and 30 were not operated upon. Out of these cases, 38 died after weeks or months; 3 patients entered a chronic apallic status; 2 patients are improving; 10 recovered with severe neurological or psychic sequels or both; 4 recovered with minimal sequels, and 5 without sequels; no patients in these two last groups were aged more than 20.

Adolescent↗
PubMed1976

[Hereditary spongiform dystrophy in young children (Canavan: van Bogaert-Bertrand)].

Hereditary spongiform dystrophy in young children is characterised by macrocephaly with spasticity, convulsions and ultimately a decerebrate state and diffuse electroencephalographic changes. Histological examination of the brain remains essential for its diagnosis. A review of the ultrastructural studies reported by various authors complements the findings obtained by conventional histology. We have thus endeavoured to determine whether van Bogaert-Bertrand's disease is to be considered as congenital or acquired. The anatomical findings in 3 cases together with the descriptions of other authors lead us to the following conclusions: -that the spongiform changes may be due to an osmolar disequilibrium in which the ATPase-Na/K relation with mitochondrial abnormalities is yet unclear. -that the constant finding of Alzheimer type II cells is certainly an indication of intra-astrocytic malfunction. -that the oedema blocks both myelin synthesis and its coiling into lamellae. Case 1, which showed a long survival compared to others described (about 4 years), enabled us to study terminal lesions. Sub-cortical zones, in both cerebrum and cerebellum, contained neither myelin nor spongiform cavities, but, on the other hand, showed a compact glio-fibrillosis with large vesicles and oligodendroglia of increased density. We have interpreted these lesions, progressively replaced by spongiosis deeper in the cortex, as evidence of retracted scar tissue. Differences found between cerebral weights seem to confirm this hypothesis.

Alzheimer Disease↗
PubMed1981

Carotid Doppler hemodynamics in posttraumatic intracranial hypertension.

Repeated Doppler sonograms were performed on the common carotid arteries of patients with severe brain injury. The evolution of the flow-wave shape in 9 patients who developed massive intracranial hypertension and finally died with cerebral circulatory arrest demonstrated that, with increasing peripheral vascular resistance, the diastolic flow diminished while the peak systolic flow was not significantly affected. Thus, the so-called pulsatility index, a measure of the pulsatile characteristic of the sonogram, can be used as a semiquantitative measure of intracranial perfusion. Measurements on healthy control subjects provided pulsatility indexes between 1.5 and 2.0. In cases of posttraumatic brain edema, these values increased gradually. These data suggest that values higher than 3 are associated with severe intracranial hypertension and the decerebrate state. In angiographically demonstrated cerebral circulatory arrest, the pulsatility index was found to range between 6 and 8.

Brain Injuries↗
PubMed2005

Continuous renal replacement therapy may aid recovery after cardiac arrest.

We report on the case of a patient who suffered a cardiac arrest in ventricular fibrillation (VF), leading to a decerebrate state, who made a rapid complete neuronal recovery following the institution of continuous renal replacement therapy (CRRT). Continuous veno-venous haemodiafiltration (CVVHDF) was used; the patient remained haemodynamically stable. Flexor responses were seen after 1 1/2 h and the patient regained consciousness within 3 h. There were no complications associated with the procedure except some minor gastric bleeding, which did not need any specific therapy.

Diabetes Complications↗