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Biomedical subjects

J R Trott

Publications and source records attributed to J R Trott.

At least 37 records · Page 2Linked to original sources
PubMed1976

The effect of low amplitude muscle vibration on the discharge of fusimotor neurones in the decerebrate cat.

1. Longitudinal vibration (50-100 mum, 100-300 Hz) has been applied to the triceps surae tendon to examine its effect on the tonic discharges of gastrocnemius medialis fusimotor neurones in the decerebrated cat. 2. For nineteen out of twenty-seven fusimotor neurones vibration consistently caused a small rise in discharge frequency. The remaining eight neurones showed no respose to the vibration which always evoked a considerable discharge in alpha motoneurones. 3. The reflex excitation of fusimotor neurones is attributed to activity in primary endings of muscle spindles since control experiments confirmed that these receptors were powerfully excited by the vibration used whereas secondary endings and Golgi tendon organs remained unaffected. 4. Tonic discharges of fusimotor neurones of unknown destination were also recorded from lumbar 7 and sacral 1 ventral root filaments in decerebrated cats. Of thirty cells, seven were inhibited, five were excited and the remaining eighteen units were unaffected by vibration of the triceps surae. 5. These findings are discussed in relation to the role of muscle stretch receptors in the autogenetic control of fusimotor neurones.

Action Potentials↗
PubMed1975

The mode of action of 5-hydroxytryptophan in facilitating a stretch reflex in the spinal cat.

1. Intravenous injection of 5-hydroxytryptophan (5-HTP) excites discharges of gamma motoneurones to extensor muscles of the hind limbs of decerebrate spinal cats and this occurs with a short latency (1-2 min). 2. 5-HTP also facilitates the stretch reflex in the spinal cat but, in contrast, there is a latency of about 10 min with a maximum action after 20 min. 3. Facilitation of the stretch reflex by 5-HTP still occurs when the gamma loop has been opened by cutting all ventral roots supplying the muscle. Thus excitation of gamma motoneurones by 5-HTP is not required for facilitation of the stretch reflex. 4. A possible contribution to the stretch reflex from the increased discharge of gamma motoneurones has been assessed. Selectively removing gamma activity rarely altered the reflex response to stretch and in only 3 out of 15 spinal cats could we conclude that gamma discharges contributed towards facilitation of the stretch reflex by 5-HTP; 5; Methysergide (0.25 mg/kg) blocked completely the facilitation of the stretch reflex caused by 5-HTP in the spinal cat but only partially antagonised the reflex in the decerebrate cat, even when injected intra-arterially close to the lumbar spinal cord. 6. Lysergic acid diethylamide (LSD) was found to mimic the actions of 5-HTP. It facilitated the stretch reflex and excited extensor gamma motoneurones in the spinal animal.

5-Hydroxytryptophan↗