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Biomedical subjects

R F Schmidt

Publications and source records attributed to R F Schmidt.

At least 127 records · Page 7Linked to original sources
PubMed1977

The spinocervical tract as a possible pathway for muscular nociception.

In decerebrate and chloralose-anaesthetized spinal cats, micro-electrode recordings were made from axons of the spinocervical tract (SCT) during intra-arterial injection of bradykinin, 5-hydroxytryptamine and potassium into the gastrocnemius-soleus (GS) muscle. The results suggest that muscular group IV and group III afferent units which respond to the above painful stimulation project into the SCT. The portion of SCT units that could be activated by injections of these algesic substances into the GS-muscle was different in spinal and decerebrate preparations, showing that the SCT neurones are subject to a descending influence. It is concluded that the spinocervical tract, in addition to its function as a cutaneous sensory pathway, may serve as a pathway for muscular nociception in the cat.

Afferent Pathways↗
PubMed1973

Cutaneous convergence on to the climbing fibre input to cerebellar Purkynĕ cells.

1. In cats anaesthetized with Nembutal, the cutaneous receptive fields of individual cerebellar climbing fibres were assessed by recording the climbing fibre responses of single Purkyne cells following controlled mechanical stimulation (air jets, vibration, taps, pressure) of the foot pads of all four limbs and of the hairy skin of the limbs and the body.2. Three major types of cutaneous receptive fields of individual climbing fibres were recognized: (a) restricted fields generally confined to the distal areas of one limb only; (b) circumscribed fields on the distal areas of two to four limbs (discontinuous fields); and (c) widespread continuous fields extending over all or almost all of the body surface. A fourth group appears to receive cutaneous inputs from one limb and sensory input from deeper structures in other limbs.3. Thresholds for tapping of the foot pads were often quite low (< 100 mum indentation), and there was no noticeable difference in the distribution of thresholds between the climbing fibres having restricted or more widespread cutaneous receptive fields. Similarly, the latencies of climbing fibre responses evoked by vibration and tapping were in the same ranges for climbing fibres with receptive fields restricted to one limb only and for those having more widespread fields.4. In regard to location in the anterior lobe of the cerebellum it was found that those climbing fibres receiving inputs only from the ipsilateral forelimb projected to Purkyne cells located almost entirely in lobule V, whereas all other climbing fibres with restricted or more widespread receptive fields projected to Purkyne cells distributed widely within lobules II to V.

Air↗
PubMed1973

Cortical and peripheral modification of cerebellar climbing fibre activity arising from cutaneous mechanoreceptors.

1. In cats anaesthetized with Nembutal climbing fibre (CF) responses evoked in individual cerebellar Purkyne cells by mechanical stimulation of the skin were conditioned by preceding stimuli both to the periphery and to the precruciate area of the cerebral cortex.2. Cortical stimulation, generally subthreshold for evoking a CF response itself, induced an inhibition of cutaneous evoked CF responses in 65% of all Purkyne cells tested. The maximum inhibition ranged from 40 to 100% of the control responses at conditioning-testing intervals of 30-70 msec and the duration of the inhibition was usually 125 msec.3. In most cases the corticofugal inhibition of cutaneously evoked CF responses was mediated by inhibitory mechanisms outside the cerebellar cortex, probably at relays within the spino-olivocerebellar pathways. Purkyne cells undergoing corticofugal inhibition were distributed widely within both the vermis and the pars intermedia of the anterior lobe.4. In 40% of all Purkyne cells tested, there was evidence for afferent inhibition of their peripherally evoked CF responses as revealed by conditioning stimuli applied to the skin outside the receptive field. Again it was found that the inhibition was exerted at levels prior to the cerebellum.5. It is concluded that the afferent input transmitted to Purkyne cells via climbing fibres can be modified by corticofugal and peripheral influences exerted on the relays of the CF pathways outside the cerebellar cortex.

Anesthesia, General↗