Actions of morphine on the segmental reflex of the decerebrate-spinal cat.
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1. The actions of morphine were studied on the segmental reflex of the decerebrate-spinal cat. Morphine decreased arterial blood pressure.2. Morphine inhibited mono- and polysynaptic reflexes. The influence of morphine on monosynaptic reflexes was more obvious at stimulation of the dorsal root at a frequency of 12.5 Hz than at 0.5 or 2.5 Hz.3. The total amount of activity recorded from the ventral root after morphine depended on whether or not the evoked reflex was maximal or submaximal.4. These actions of morphine were antagonized by naloxone. (+info)
The response to distension of the pulmonary vein-left atrial junctions in dogs with spinal section.
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1. A reflex increase in heart rate in response to pulmonary vein distension was observed in decerebrate dogs. This increase could not be totally abolished by treatment with both propranolol and bretylium tosylate. Only bilateral cervical vagotomy abolished the reflex increase in heart rate.2. A significant increase in heart rate occurred in a total of seventeen spinal dogs during pulmonary vein distension.3. In seven spinal animals in which blood pressure was maintained by the continuous infusion of noradrenaline, the increase in heart rate could be totally prevented by cervical vagotomy.4. The time course of the increase in heart rate observed in the spinal animals was rapid, reaching maximum expression within 10 sec of pulmonary vein distension. Such a time course is dissimilar from that associated with pulmonary vein distension in intact or decerebrate dogs in which maximum increases in heart rate take 1-3 min to develop.5. It is concluded that the reflex tachycardia resulting from pulmonary vein distension may be mediated by both an efferent sympathetic and an efferent vagal pathway, the relative significance of each component being dependent upon the prevailing autonomic drive existent in the animal at any specific time. (+info)
Role of the sympathetic nervous system in daunomycin-induced arrhythmia in the monkey.
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1. Infusion of daunomycin 50 mg/kg in the monkey consistently induced ventricular arrhythmias which were not influenced by bilateral vagotomy.2. A central sympathetic component to the arrhythmias was suggested because spinal transection, ganglionic blockade or bilateral stellate ganglionectomy prevented any alterations in the e.c.g.3. Bilateral adrenalectomy or splanchnic nerve section protected three of six animals. This source of catecholamines may not be necessary in every case to initiate the arrhythmia.4. Guanethidine was a relatively ineffective antiarrhythmic agent. Timing appears to be important with this agent.5. Pargyline, by monoamine oxidase inhibition or other mechanisms, significantly lowered the arrhythmic dose of daunomycin. Reserpine pretreatment, on the other hand, prevented any e.c.g. alterations following daunomycin.6. Phenoxybenzamine exerted significant protection which may be related to its cardiodepressant properties.7. Alterations in e.c.g. were seen in all (+)-propranolol pretreated animals, although the arrhythmic period was modified in two of three experiments. Racemic (+/-) propranolol, which exerts direct myocardium depression as well as beta-adrenoceptor blockade, was completely protective in four of five experiments. The results of the present experiments indicate that the sympathetic nervous system is intimately involved in the daunomycin arrhythmia. (+info)
The effects of somatic stimuli on the bladder in the cat.
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1. Measurement of the intra-vesical pressure in cats during contractions of the bladder was found to be a more reliable method of studying bladder function than the cystometrogram. Under suitable conditions the pressure curves of these bladder contractions were constant and could be examined statistically.2. In the anaesthetized cat cold decreased the pressure developed by bladder contractions and shortened the interval between them. There was no evidence that this effect was reflex in nature.3. In the anaesthetized cat stimulation of the sural nerve sometimes produced contraction of the bladder or increased the pressure developed by spontaneous contractions.4. In the anaesthetized cat stimulation of any hind-limb nerve from muscles with conduction velocities of approximately 50 m/sec inhibited bladder contractions.5. In the acute spinal cat somatic stimuli had no effect on bladder activity.6. In the chronic spinal cat cutaneous stimuli produced reflex contraction of the bladder or the augmentation of a spontaneous contraction. Stimulation of nerves from hind-limb muscles, however, had no effect on bladder activity.7. In the decerebrate cat cutaneous stimuli increased bladder activity, and this was probably ;reflex' in nature. Stimulation of nerve fibres from hind-limb muscles either produced bladder contractions or augmented spontaneous contractions. (+info)
Vesico-somatic reflexes in the chronic spinal cat.
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1. In cats anaesthetized with chloralose whose spinal cords were transected 6-7 weeks previously, spontaneous contractions of the bladder had no effect on mono- or polysynaptic reflexes recorded electrically from the cut lumbar ventral spinal roots.2. In the same cats contractions of the bladder decreased hind-limb extensor and flexor reflexes recorded myographically.3. The effects of (a) pelvic nerve stimulation and distension of the bladder on mono- and polysynaptic reflexes and (b) the effects of bladder contractions on hind-limb reflexes recorded myographically in acute and chronic spinal, decerebrate and anaesthetized cats are discussed.4. The sites of interaction between vesical and somatic reflexes are discussed and further evidence is presented that bladder contractions affect the gamma-loop. (+info)
Recurrent inhibition in sacral parasympathetic pathways to the bladder.
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1. The effects produced by stimulation of the central end of transected ventral roots were observed on spontaneous and evoked vesical contractions and on the firing of sacral parasympathetic neurones.2. Recurrent inhibition of sacral parasympathetic neurones was demonstrated at frequencies of stimulation above 10/sec and at intensities above threshold for the parasympathetic axons.3. Recurrent inhibition was present in chloralose cats, as well as in decerebrate animals and was unaffected by chronic spinal transection.4. Interneurones were located which are presumed to be the autonomic equivalents of the somatic Renshaw cells. They were synaptically activated by antidromic stimulation of preganglionic fibres in sacral ventral roots.5. The inhibition of vesical contractions and the firing of the interneurones was reduced when the intravesical pressure was raised.6. The recurrent inhibition was unaffected by the intravenous injection of dihydro-beta-erythroidine.7. Strychnine reduced the recurrent inhibition in some experiments but the results were inconsistent. The effects of picrotoxin were inconclusive.8. The possible role of recurrent inhibition in micturition is discussed. (+info)
Termination and functional organization of the dorsal spino-olivocerebellar path.
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1. The spino-olivocerebellar path ascending through the dorsal funiculus (DF-SOCP) was investigated in decerebrate cats with the cord transected in the third cervical segment except for the dorsal funiculi. The climbing fibre responses evoked in Purkinje cells were studied by recording the mass activity at the cerebellar surface and by recording from single cells.2. The DF-SOCP forms a disynaptic path from the spinal cord to the cerebellar cortex as shown by latency measurements. Anatomical studies have recently demonstrated that the relays are in the rostral part of the dorsal funiculus nuclei and in the dorsal accessory olive.3. The DF-SOCP projects to sagittal zones in the pars intermedia and vermis of the anterior lobe. The somatotopical organization is predominantly transverse in the pars intermedia and predominantly longitudinal in the vermis.4. The olivary neurones in the DF-SOCP are activated by the flexor reflex afferents from wide receptive fields. The fields are restricted to one ipsilateral limb and the majority of the olivary neurones could be activated from all the nerves tested in this limb.5. Natural stimulation of receptors evoked excitation in about half of the olivary neurones investigated. This excitation was elicited by pressure against deep structures. Inhibitory effects were rarely observed.6. The dorsal and ventral spino-olivocerebellar paths are compared. (+info)
Reflexes to sacral parasympathetic neurones concerned with micturition in the cat.
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1. Reflexes to sacral parasympathetic neurones were studied by electrophysiological techniques in decerebrate, in chloralose-anaesthetized, and in chronic spinal cats.2. Excitatory reflexes from pelvic nerve and sacral somatic afferent nerve fibres were present before and after chronic transection of the spinal cord, but the latencies differed markedly. It was concluded that the long-latency reflexes observed when the spinal cord was intact involved long-loop reflexes to the brain-stem. The weak, short-latency reflexes in the chronic spinal cat were never observed when the spinal cord was intact and could be due to reorganized spinal connexions. The short-latency reflexes are probably unimportant in normal micturition.3. Stimulation of afferent fibres in the pelvic or sacral somatic nerves produced short-latency inhibitory post-synaptic potentials (IPSPs) and inhibition of discharges in parasympathetic neurones. This inhibition was due to a spinal reflex.4. A local reflex was demonstrated in the pelvic plexus. This was probably a cholinergic axon reflex, but the remote possibility that it was a local cholinergic reflex involving sensory neurones in the bladder wall has not been excluded. (+info)