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Biomedical subjects

H Shimazaki

Publications and source records attributed to H Shimazaki.

8 recordsLinked to original sources
PubMed1990

Physiological properties of projection neurons in the monkey striatum to the globus pallidus.

In order to study neuronal information transfer from the striatum to the globus pallidus (GP) during voluntary movement, we recorded activity of electrophysiologically identified projection neurons in the putamen to the GP while the monkey was performing learned movement tasks. Two categories of putamen neurons were recorded: one with tonic spontaneous discharges at about 2-7 impulses/s responded to external sensory stimuli (type I); the other with very low spontaneous discharge rates less than 0.5 impulses/s showed phasic burst discharges which were time-locked to limb or orofacial movements (type II). All of the putamen neurons identified as projecting to the GP (external and/or internal segment) by an antidromic activation from electrical stimulation of the GP were type II cells. It was concluded that the movement-related activity of type II putamen neurons is transferred to GP and/or SN during voluntary movement but tonically active type I cells do not project to the GP.

Action Potentials↗
PubMed1976

Synaptic transmission from photoreceptors to bipolar and horizontal cells in the carp retina.

The most important observations in the present study can be summarized as follows: 1. In horizontal and bipolar cells, blocking chemical transmission caused membrane potential changes of the same polarity as the responses to illumination in each cell type. 2. Acceleration of transmitter release from the receptor terminals depolarized the horizontal cells, which is the opposite polarity to the light response. 3. Stimulation by transretinal current flowing from receptor side to vitreous side depolarized the receptor terminals and triggered transmitter release, which in turn evoked transient postsynaptic potentials in horizontal and bipolar cells. The polarity of the postsynaptic responses was the opposite to that of the light-evoked responses in each type of cell. 4. Hyperpolarization of the receptor terminals by the current of relatively long duration flowing from vitreous side to receptor side reduced the transmitter release, as demonstrated by the horizontal cell hyperpolarization. 5. From these observations, it is inferred that the receptors release the transmitter in the dark and that the transmission depolarizes horizontal and off-center bipolar cells by increasing membrane permeability chiefly to Na+ and hyperpolarizes the on-center bipolar cell by decreasing membrane permeability to Na+.

Animals↗
PubMed1975

Effects of external ions on the synaptic transmission from photorecptors to horizontal cells in the carp retina.

1. Intracellular recordings were made from cones and horizontal cells of the isolated carp retina and the mechanisms of synaptic transmission from cones of horizontal cells were studied by changing the ionic composition of the external medium. 2. Cones were depolarized and their light responses enhanced in low Ca high-Mg medium. In the same medium, in which chemical transmission is suposed to be blocked, horizontal cells were hyperpolarized and their light responses disappeared. 3. When the synaptic input was removed, the membrane potential of horizontal cells agreed well with Ek. 4. In Na-free medium both cones and horizontal cells were hyperpolarized and response disappeared. On reaplication of normal Ringer, horizontal cells showed a trenaient membrane potential reversal (inside positive), indicating that the horizontal cell has a high Na permeability under the influence of the endogenous transmitter. 5. Application of La produced little change in cones, while it strongly depolarized horizontal cells...

Animals↗