The effects of electrical stimulation of viseral afferent nerve fibres on monosynaptic and polysynaptic reflex responses

SUIMMARY1. Monosynaptic reflexes, evoked from flexor and extensor hind limb muscle nerves in cats anaesthetized with pentobarbitone sodium, were depressed for several seconds after right intra-atrial injection of phenyl diguanide. Injection of the drug close to the aortic valves did not produce the same effect on the reflex. There was no obvious depression of polysynaptic reflexes on intra-atrial injection of phenyl diguanide.2. This depression of the monosynaptic reflex was present even after the administration of atropine, which lessened the hypotension due to phenyl diguanide. The blood gas tensions were also measured after the administration of phenyl diguanide, and were not altered to a degree where one would expect the depression to be secondary to a change in arterial gas tensions. The depression was also present in paralysed and artificially ventilated cats. 3. The afferent pathway causing this depression of the monosynaptic reflex runs in the vagus nerve, as shown by experiments done before and after vagotomy. Intercollicular decerebration also abolished this inhibition of the monosynaptic reflex.4. Prior intravenous injection of strychnine (01 mg/kg) abolished the effect of intra-atrial administration of phenyl diguanide.5. It was concluded that stimulation of type J pulmonary endings causes a reflex inhibition of monosynaptic reflexes lasting for several seconds via regions of the brain cephalad to the intercollicular level.

Section: Methodscontrasting

confidence: 38%

Reflex inhibition of monosynaptic reflexes by stimulation of type J pulmonary endings

Deshpande¹,

Devanandan²

1970

“…The only differences from the methods employed in previous papers (Evans & McPherson, 1958, 1960and McPherson, 1966a were (a) the method of myograph recording and (b) the level of transection of the spinal cord. In the present series of experiments muscle contractions were recorded using a rectilinear potentiometer fed through a d.c. amplifier to a potentiometric recorder.…”

Section: Methodsmentioning

confidence: 96%

Vesico‐somatic reflexes in the chronic spinal cat

McPherson¹

1966

SUMMARY1. 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 y-loop.

“…It is also possible that these inhibitory pathways are themselves inhibited when voluntary restraint is removed. In addition to these primary reflex mechanisms there may be other associated reflexes of minor importance in the regulation of micturition (see Garry et al 1959;Evans & McPherson, 1960). Thus, there is a progressive and self-reinforcing cycle which increases and maintains the contraction of the vesical musculature during the act of voiding.…”

Section: Discussionmentioning

confidence: 99%

Reflexes to sacral parasympathetic neurones concerned with micturition in the cat

Groat¹,

Ryall²

1969

256

129

SUMMARY1. 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 longlatency reflexes observed when the spinal cord was intact involved longloop 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.