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H T Chang

Publications and source records attributed to H T Chang.

At least 109 records · Page 6Linked to original sources
PubMed1983

The morphology of intracellularly labeled rat subthalamic neurons: a light microscopic analysis.

Light microscopic analysis of rat subthalamic (STH) neurons which were intracellularly labeled with horseradish peroxidase, following the acquisition of electrophysiological data, revealed the following: (1) The somata of STH neurons were polygonal or oval with occasionally a few somatic spines. Usually three or four primary dendrites arose from the soma. Dendritic trunks tapered slightly and divided into long, thin, sparsely spined branches. Dendrites of some STH neurons extended into the cerebral peduncle. (2) Reconstruction of the dendritic field was made in three different planes. In either sagittal or frontal planes, the dendritic field was usually oval and the long axis was parallel to the main axis of STH. In the horizontal plane, the dendritic field of all neurons was polygonal. (3) The axons of all the neurons analyzed originated from the soma and were traced beyond the borders of STH, thus indicating that they were projection neurons. All the parent axons bifurcated at least once. After bifurcation, one axon branch coursed dorsolaterally within the cerebral peduncle and terminated in the globus pallidus. The other branch coursed caudally or mediocaudally and arborized in the substantia nigra. Frequently, the axon branches projecting toward the globus pallidus emitted fine axon collaterals within the entopeduncular nucleus. (4) About one-half of the analyzed STH neurons had intranuclear axon collaterals. The neurons with intranuclear collaterals had a higher dendritic tips/stems ratio than neurons without intranuclear collaterals. This observation indicated that STH neurons could be divided into two groups according to their axonal morphology. (5) The axonal terminal arborization observed in all the target sites (i.e., globus pallidus, entopeduncular nucleus, STH, and substantia nigra) were formed with varicose collateral branches which also gave rise to short filaments with beaded endings. Some of these projection neurons could therefore communicate with the target neurons in the globus pallidus, substantia nigra, entopeduncular nucleus, as well as STH through their collateral system.

Animals↗
PubMed1983

Pallidal inputs to subthalamus: intracellular analysis.

Neuronal responses of the subthalamic nucleus (STH) to stimulation of the globus pallidus (GP) and the substantia nigra (SN) were studied by intracellular recording in the decorticated rat. (1) GP and SN stimulation evoked antidromic spikes in STH neurons with a mean latency of 1.2 ms and 1.1 ms, respectively. Based on the above latencies, the mean conduction velocity of the STH neurons projecting toward GP was estimated to be 2.5 m/s, and that toward SN was 1.4 m/s. Many STH neurons could be activated following stimulation of both GP and SN, indicating that single STH neurons project to two diversely distant areas. In spite of differences in conduction distance of GP and SN from STH, differences in the conduction velocities of bifurcating axons make it possible for a simultaneous arrival of impulses in the target areas to which these STH neurons project. (2) GP stimulation evoked short duration (5-24 ms) hyperpolarizing potentials which were usually followed by depolarizing potentials with durations of 10-20 ms. These potentials were tested by intracellular current applications and intracellular injections of chloride ions. The results indicated that the hyper- and depolarizing potentials were IPSPs and EPSPs respectively. These IPSPs were considered to be monosynaptic in nature since changes in the stimulus intensities of GP did not alter the latency of IPSPs. The mean latency of the IPSPs was 1.3 ms. Based on the above mean latency the mean conduction velocity of GP axons projecting to STH was estimated to be 3.8 m/s. (3) Analysis of electrical properties of STH neurons indicated that: (i) input resistance estimated by a current-voltage relationship ranged from 9 to 28 M omega; (ii) the membrane showed rectification in the hyperpolarizing direction; (iii) direct stimulation of neurons by depolarizing current pulses produced repetitive firings with frequencies up to 500 Hz. (4) Morphology of the recorded STH neurons was identified by intracellular labeling of neurons with horseradish peroxidase. Light microscopic analysis indicated that the recorded neurons were Golgi type I neurons with bifurcating axons projecting toward GP and SN.

Animals↗
PubMed1983

Origins of post synaptic potentials evoked in spiny neostriatal projection neurons by thalamic stimulation in the rat.

Stimulation of thalamic intralaminar nuclei or structures along the intrathalamic trajectory of thalamostriatal axons evoked complex EPSPs and subsequent hyperpolarizations in rat neostriatal spiny neurons identified by intracellular injection of horseradish peroxidase and/or antidromic activation from substantia nigra. In intact urethane-anesthetized rats, the initial EPSP portion of the response consisted of several components and lasted up to 75 ms. Short (1-10 ms) latency components exhibiting latency variations suggestive of a polysynaptic origin were often observed, and sometimes were the earliest components of the response. However, individual components of the excitatory response could not be clearly distinguished in most neurons and the earliest excitatory component usually appeared to be monosynaptic. After large acute aspiration lesions of ipsilateral cerebral cortex, the early polysynaptic EPSP components of thalamic-evoked EPSPs were absent or greatly attenuated. This suggested that most or all of the short latency polysynaptic EPSP components arose via a thalamo-cortico-striatal route. A short latency (1.6-4.0 ms) monosynaptic EPSP and a second excitatory component with a longer and more variable latency (8-28 ms) remained intact after acute decortication. These were not dependent upon intact corticothalamic or corticostriatal axons, since they were both still present in experiments performed as long as 4 days following ipsilateral hemidecortication. The longer latency excitatory response was shown to be polysynaptic by its latency variation with changes in stimulus intensity and frequency. This component of the response was abolished after acute thalamic hemitransections separating thalamostriatal neurons from their axons. In these experiments, stimulation of thalamostriatal axons rostral to the transection continued to evoke monosynaptic EPSPs in neostriatal spiny neurons. These EPSPs ranged from 1.8 to 3.0 ms in latency, had peak amplitudes up to 11 mV and were 20-37 ms in duration.

Animals↗
PubMed1983

Disfacilitation and long-lasting inhibition of neostriatal neurons in the rat.

Excitatory postsynaptic potentials evoked in rat neostriatal spiny projections neurons were followed by a long (100-300 ms) period of membrane hyperpolarization, followed in turn by a late depolarization. Concomitant with these changes in membrane potential were inhibition and subsequent excitation of spontaneous firing and excitatory activity evoked from substantia nigra and cerebral peduncle, but not from cortical stimulating sites. Thalamic-evoked excitatory activity was sometimes sensitive and sometimes insensitive to this inhibition, which has previously been believed to result from intrinsic inhibitory synaptic activity among neostriatal neurons. In intracellular recordings from neostriatal neurons in urethane anesthetized rats this long-lasting inhibitory response (1) exhibited alterations with intracellularly applied steady currents comparable to those of the EPSP, (2) failed to respond to intracellular injection of chloride ions, (3) was associated with either a decrease or no detectable change in the input conductance of the neurons, and (4) was abolished after lesions that interrupted polysynaptic pathways to neostriatum through intracortical and intrathalamic synaptic circuits. These findings indicate that the long lasting inhibitory portion of the responses of neostriatal neurons arises from a phasic inhibition of tonically active corticostriatal and thalamostriatal neurons and a concurrent decrease in the excitability of polysynaptic pathways converging on neostriatal neurons.

Afferent Pathways↗
PubMed1983

Clinical observation on the uterotonic effect of I-mu Ts'ao (Leonurus artemisia).

Normal fertile women given an oral dose of I-mu Ts'ao decoction (30 g. dry weight equivalent) showed an increase in intra-uterine pressure in 41.3% of 121 cases. The increase ranged from 150% to over 300% of spontaneous activity before dosing. A slightly higher success rate was observed with 2 successive doses or with improved experimental skill in later cases. Ergonovine (0.2 mg i.m.) scored a success rate of 61%. Therefore, I-mu Ts'ao decoction appeared to have a relative potency of 91% compared with ergonovine when the highest success rate (55.5%) of the former is considered. Blank control with water yield a positive response rate of 2.7%. There are no observable side-effects apart from diuresis.

China↗
PubMed1982

A Golgi study of rat neostriatal neurons: light microscopic analysis.

At least two types of large neurons (somatic cross-sectional areas, SA greater than 300 microns2) and five-types of medium neurons (SA between 100 and 300 microns2) were distinguished in Golgi preparations of the adult rat neostriatum. Type I large cells had aspinous somata with long, radiating, sparsely spined dendrites which were sometimes varicose distally, whereas type II large cells had spines on both somatic and dendritic surfaces. Type I medium cells had aspinous somata and proximal dendrites, but their distal dendrites were densely covered with spines. Type II medium cells had somatic spines, and their radiating dendrites were sparsely spined. Other medium cells had no somatic spines: Type III cells had poorly branched and sparsely spined dendrites. Type IV cells had profusely branched, sparsely spined dendrites. Type V cells had radiating and varicose dendrites which could also be sparsely spined. Several small neurons (SA mostly less than 100 microns2) were also found in the rat neostriatum: Some had aspinous soma with sparsely spined dendrites; others had somatic spines. Except for the type II large cells, intrinsic axon collaterals were observed for every type of neuron, indicating that they all had local integrating functions.

Animals↗
PubMed1982

Origins of postsynaptic potentials evoked in identified rat neostriatal neurons by stimulation in substantia nigra.

Responses of striatal neurons to stimulation in substantia nigra were recorded intracellularly in intact rats and after acute or chronic unilateral lesions of cerebral cortex or after combined cortical lesions and unilateral thalamic transections. Spiny striatal efferent neurons were identified by intracellular injection of horseradish peroxidase. In intact animals substantia nigra stimulation evoked a complex response with both excitatory and inhibitory phases. Acute unilateral decortication abolished the inhibitory phase of the response and reduced the amplitude of the initial EPSP. Thus, part of the excitatory phase and most or all of the inhibitory phase of the response result from polysynaptic routes to striatum involving cerebral cortex. The remaining EPSP observed in acute decorticate animals exhibited two components distinguished on the basis of their time courses. The latter of these was abolished by thalamic transections. The earlier component was shown to be a monosynaptic EPSP evoked by axon collaterals of cortical efferent neurons projecting to brainstem and was not observed in animals subjected to chronic decortication. After removal of all of these non-nigral response components a small long latency EPSP could be evoked by nigral stimulation. The EPSP is probably due to activation of dopaminergic nigro-striatal axons.

Animals↗
PubMed1982

Morphological and physiological properties of neostriatal neurons: an intracellular horseradish peroxidase study in the rat.

The physiological and morphological (light and electron microscopic) properties of four categories of neostriatal neurons (two types of medium spiny cells and two types of aspiny cells) were analyzed using the technique of intracellular recording and intracellular labeling with horseradish peroxidase. All of the neurons in this study had excitatory responses following stimulation of the cortex and substantia nigra except for the large aspiny neuron for which only substantia nigra inputs were tested. Morphologically, these neurons differed with respect to the size and shape of their somata, density and distribution of dendritic spines and distribution of their axons and axon collaterals. Ultrastructurally, observed somatic differences included the quantity and distribution of organelles and conformation of the nuclear envelope. The axons of one type of medium spiny neuron and the large aspiny neuron were myelinated. Unmyelinated axon collaterals arose from the axons of both types of medium spiny neurons and formed synapses on the dendritic shafts and possibly with the necks of spines of other neostriatal neurons. The parent axons of the most common type of medium spiny neurons were followed to the globus pallidus and, in some cases, to the internal capsule.

Animals↗
PubMed1982

Large neostriatal neurons in the rat: an electron microscopic study of gold-toned Golgi-stained cells.

The large neurons in the rat neostriatum consist of at least two morphologically distinct types in Golgi preparations: Type I large cells had smooth somata whereas type II large cells had somatic spines. In the present study, the ultrastructural morphology of the Golgi-stained large neostriatal neurons in the rat was analyzed by the gold-toning technique. In addition, the ultrastructural morphology of type I medium (spiny) neurons was also studied for comparison. The results revealed that the type I medium neurons had unindented nucleus with small amount of organelles whereas both types of large neostriatal neurons had deeply indented nucleus and large amount of cytoplasmic organelles. The type I large neurons had much fewer synaptic contacts on the somata than the type II large neurons, the latter also had synapses on their somatic spines. Our data also support the possibility that some large neostriatal neurons may have long axons by the fact that some of these cells had myelinated axons. Our result should be very useful in interpreting morphological data obtained with techniques such as immunocytochemistry or retrograde labeling which enables only partial labeling of somata and dendrites.

Animals↗
PubMed1982

Roles of acupuncture in medicine.

The medical thinking of traditional Chinese medicine is considered to stem mainly from the theory formulated for acupuncture, as evidenced by the preponderant discussions of acupuncture in "Nei Ching", a classic of Chinese Medicine. Acupuncture cannot do much to those diseases which involve irreversible organic damage. It is essentially a technique for correcting the reversible physiological malfunction of various parts of the body by physiological means. It is believed possible that the acupuncture-initiated impulses may activate the autonomic centers and the hypophysical system in the brain so as to improve the efficiency of homeostatic and self-defence mechanisms of the body. Recent studies in acupuncture analgesia have contributed much to the understanding of the neural mechanism of pain and its control. Modern medicine should accept acupuncture as an alternative in medical practice as advocated by William Osler whose viewpoint about the value of acupuncture is cited.

Acupuncture Therapy↗
PubMed1981

Single neostriatal efferent axons in the globus pallidus: a light and electron microscopic study.

Intracellularly labeled rat neostriatal projection neurons were analyzed with both light and electron microscopy. The axons of medium spiny neurons were traced into the globus pallidus and were found to make synaptic contacts with pallidal dendrites. Despite the common somato-dendritic morphology of the neostriatal projection neurons, two different distribution patterns of efferent axons were observed, indicating the presence of functionally different medium spiny neurons in the neostriatum.

Animals↗