Biomedical subjects
Publications and source records attributed to K Toyama.
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1. The cerebellar integration of sensory inputs to Deiters neurones was studied in cats under Nembutal anaesthesia.2. Stimulation of peripheral nerves produced in the Deiters neurones a sequence of an initial excitatory post-synaptic potential (e.p.s.p.) and a later inhibitory post-synaptic potential (i.p.s.p.), or a relatively small e.p.s.p.3. The Deiters neurones were classified as forelimb (FL)- or hind limb (HL)-type cells according to the location of the most effective peripheral nerve. In the FL cells stimulation of the forelimb nerves produced the e.p.s.p.-i.p.s.p. sequence (dominant response), while stimulation of the hind limb nerves was ineffective or produced the small e.p.s.p. (non-dominant response). In contrast, in the HL cells the non-dominant response was evoked from the forelimb nerves, and the dominant response from the hind limb nerves.4. The stimulus intensity-response relation indicates that Group I and II muscle afferents and low and high threshold cutaneous afferents contribute to the dominant and non-dominant responses.5. Antidromic identification of these Deiters neurones revealed that 90% of the HL cells and 85% of the FL cells project to the lumbo-sacral and cervico-thoracic segments of the spinal cord, respectively, while 10% of the HL cells and 15% of the FL cells innervate the cervico-thoracic and lumbo-sacral segments, respectively.6. The mean latency of the e.p.s.p. evoked from the forelimb nerves was 14 msec in the FL cells and 13 msec in the HL cells, and the latency of the e.p.s.p. evoked from the hind limb nerves was 17 msec in the FL cells and 18 msec in the HL cells. The later i.p.s.p. regularly followed the onset of the e.p.s.p. with a delay of 3-5 msec.7. The dominant and non-dominant responses in both types of cells exhibited the following three characteristic features: (i) a strong depression after conditioning stimulation of the inferior olive, (ii) an increase of the inferior olivary excitability during the responses, and (iii) a striking frequency depression with stimulation at relatively low frequency (5-10/sec).8. Consequently it was concluded that all of the responses were produced through the climbing fibres originating from the inferior olive, the i.p.s.p.s due to inhibition from Purkyne cells activated by the climbing fibres and the e.p.s.p.s due to excitation from the collaterals of the climbing fibres.
1. The cerebellar integration of sensory inputs to Deiters neurones was investigated in decerebrate cats. In some preparations decerebration was combined with transection of the olivocerebellar fibres.2. In the latter preparations peripheral nerve impulses generally produced a response consisting of a sequence of the following post-synaptic potentials: (i) an initial e.p.s.p. (d(1)), (ii) early i.p.s.p. (h(1)), (iii) later i.p.s.p. (h(2)).3. The mean latencies of d(1), h(1) and h(2) were 5.7, 7.3 and 9.8 msec from the forelimb nerves, and 7.5, 9.0 and 13.4 msec from the hind limb nerves, respectively.4. The stimulus intensity-response relation indicates that the Group I muscle afferents as well as the low threshold cutaneous afferents contribute to the response.5. In the preparations with the intact inferior olive there were additional components of the post-synaptic potentials: a later e.p.s.p. (d(2)) and another later i.p.s.p. (h(3)), their mean latencies being 15.3 and 19.7 msec from the forelimb nerves, and 18.0 and 21.3 msec from the hind limb nerves, respectively.6. The d(1) and h(2) components were attributed to the mossy fibre afferents and d(2) and h(3) to the climbing fibres; d(1) and d(2) were due to excitation through the collaterals of the mossy and climbing fibres, and h(2) and h(3) to inhibition from Purkyne cells activated by the mossy and climbing fibres, respectively. h(1) was too early to be produced through the cerebellum, and was probably mediated by inhibitory neurones in the reticular formation.
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The resting membrane of a barnacle muscle fiber is mostly permeable to cations in a solution of pH 7.7 whereas it becomes primarily permeable to anions if the pH is below 4.0. Mechanisms of ion permeation for various monovalent cations and anions were investigated at pH 7.7 and 3.9, respectively. Permeability ratios were obtained from the relationship between the membrane potential and the concentration of the test ions, and ionic conductances from current-voltage relations of the membrane. The permeability sequence for anions (SCN > I > NO(3) > Br > ClO(3) > Cl > BrO(3) > IO(3)) was different from the conductance sequence for anions (Br, Cl > ClO(3), NO(3) > SCN). In contrast, the permeability and conductance sequences were identical for cations (K > Rb > Cs > Na > Li). The results suggest that anion permeation is governed by membrane charges while cation permeation is via some electrically neutral mechanism.
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