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Biomedical subjects

T I Lidsky

Publications and source records attributed to T I Lidsky.

At least 37 records · Page 2Linked to original sources
PubMed1992

Clozapine's mechanisms of action: non-dopaminergic activity rather than anatomical selectivity.

The mechanisms of clozapine's unusual actions were investigated in anesthetized rats. Sensory field potentials were recorded in the nucleus accumbens, striatum and somatosensory cortex. Both haloperidol and clozapine suppressed responses in the striatum and accumbens. Clozapine's but not haloperidol's subcortical actions were unaffected by dopamine depletion. In addition, the cortical effects of the two drugs differed. These data indicate that clozapine has non-dopaminergic activity but no particular specificity for limbic basal ganglia structures. While it is known that clozapine acts as a serotonergic and cholinergic antagonist, several considerations suggest that action on still another transmitter system, possibly glutamate, needs to be investigated.

Animals↗
PubMed1990

Nerve conduction studies in chickens given phenyl saligenin phosphate and corticosterone.

Clinical signs of delayed neuropathy were induced in adult white leghorn chickens given the organophosphorus ester phenyl saligenin phosphate (PSP, 2.5 mg/kg im) 22-24 d before assessment of nerve conduction parameters. Damage to the myelinated sensory portion of the sciatic nerve was indicated by abnormal compound action potentials in treated chickens. In particular, the amplitude of the A beta response was markedly reduced. In addition, the A beta fibers did not respond normally to increasing stimulation intensity. These parameters were more like controls in chickens that had been given PSP and 30 ppm corticosterone for 11 d, beginning 1 d before PSP administration. These studies indicated that nerve conduction parameters could distinguish peripheral nerve damage in chickens given PSP and improvement could be noted in chickens treated with corticosterone.

Action Potentials↗
PubMed1989

The effects of movements on caudate sensory responses.

The aim of this experiment was to assess the effects of movement on somatosensory processing in the caudate nucleus. Units were recorded extracellularly in the caudate of awake partially restrained cats. Unit responses were evoked by either natural stimuli (brushing and skin indentation) or transcutaneous electrical stimulation. Response patterns evoked by stimuli presented when the cat was at rest were compared to responses evoked by similar stimuli presented when the cat was either making buccolingual movements or turning its head. In the majority of cases, movement suppressed caudate somatosensory responses. However, impressive augmentation of responses was seen in some cells with either type of movement.

Action Potentials↗
PubMed1988

Striatal influences on paravermal cerebellar activity.

Units were recorded extracellularly in paravermal cortex (lobule VI) of the cerebellum of chloralose anesthetized cats. Electrical stimulation of the striatum evoked excitation followed by inhibition in these neurons. In addition, the somatosensory properties of these cells were also affected by the striatum. A conditioning-test paradigm (C-T) was used in which conditioning stimulation was applied to the striatum. Test responses were evoked in cerebellar neurons by facial stimulation. As a function of the C-T interval, striatal stimulation could either enhance or suppress the test facial responses. In another procedure, a moveable electrode was used to map the thresholds for affecting the cerebellum from different points in the striatum. The lowest mean threshold was in the putamen followed respectively by the internal capsule and caudate nucleus. Control experiments suggested that striatal effects on the cerebellum were due neither to extra-striatal current spread nor antidromic activation of corticostriatal fibers. These data were discussed with regard to models of striatal motor functioning that indicate a role in postural control and sensory gating.

Action Potentials↗
PubMed1987

Influences of the basal ganglia on the medullary reticular formation.

Units were recorded extracellularly in the medullary reticular formation of chloralose-anesthetized cats during electrical stimulation of the basal ganglia (BG). Stimulating portions of the BG (caudate nucleus, entopeduncular nucleus, substantia nigra) evoked unit responses in a considerable proportion of these neurons. The majority of reticular cells that were affected by the BG were also receptive to somatic sensory inputs from the face. These units' sensory properties were influenced by BG stimulation. Cells exclusively responsive to either BG or facial inputs were uncommon. The areas of the reticular formation affected by the BG give rise to portions of the reticulospinal tracts and thereby afford the BG access to the final common path.

Animals↗
PubMed1987

Peripheral neuropathy of dietary riboflavin deficiency in chickens.

A strain of rapidly growing meat-type chickens was fed a diet deficient in riboflavin from 1-40 days of age. Diminished growth rate, progressive gait abnormality and reluctance to move were noted beginning on day 8. Neurologic abnormalities were related to peripheral neuropathy characterized by Schwann cell hypertrophy and degeneration with cytoplasmic lipid droplets' and segmental demyelination. Lesions were initially detected on day 10, and in concert with clinical signs became more profound between days 14 and 21. Sequestration of myelin debris within Schwann cells was common. Other features of the neuropathy included the presence of endoneurial edema and axonal degeneration involving small numbers of fibers. Remyelination of peripheral nerve fibers in birds on the deficient diet was occasionally seen on day 10, became progressively more prominent, and was marked by day 37. There was an associated, variable but incomplete, clinical improvement evident in later stages of the study. Liver concentrations of riboflavin in deficient birds were significantly reduced on day 13 but not on day 26. This neuropathy may be related to diminished tissue levels of the riboflavin-based coenzymes flavin-adenine dinucleotide (FAD) and flavin mononucleotide (FMN) leading to reduced cellular energy levels and profoundly affecting Schwann cells at some critical point in growth.

Animals↗
PubMed1986

Caudate neuronal activity in cats during head turning: selectivity for sensory-triggered movements.

Units were recorded extracellularly from the caudate nucleus (CN) of cats during movement. The majority of CN units fired during sensory-triggered movements rather than movements in general. However, sensory stimulation was a necessary but not a sufficient condition for CN unit responding; stimuli caused unit responses only when movements were evoked. Additionally, only movements triggered by particular stimuli were associated with unit responding. These unit responses were not sensory because neural activity changes were associated with movement onset rather than stimulus presentation. These data are in accord with recent suggestions of a sensory-based motor function for the basal ganglia.

Animals↗
PubMed1985

Substantia nigra projection to medullary reticular formation: relevance to oculomotor and related motor functions in the cat.

Wheat germ lectin-horseradish peroxidase was injected into the medial medullary reticular formation in 4 cats. Retrogradely labeled cell bodies were observed in the ipsilateral substantia nigra pars reticulata and bilaterally in the superior colliculus, oculomotor nucleus and fastigial nucleus of the cerebellum. The nigral projection to this reticular formation area, which receives diffuse afferents from cortex, cerebellum, oculomotor system and vestibular nucleus and projects to spinal cord, may be of some relevance in understanding the nigral role in postural, head- and eye-movement control.

Animals↗
PubMed1985

A consideration of sensory factors involved in motor functions of the basal ganglia.

There is a sizeable literature concerning basal ganglia (BG) functioning that is based on data from experiments employing a method of analysis that is traditionally used with other motor areas. A brief review of this literature is presented and the following conclusion is reached: as compared to the success of traditional methodologies in elucidating the workings of other motor systems, their use in BG investigations has proven disappointing. A possible reason for the shortcomings of traditional analyses in BG research is discussed. The remainder of this review concerns an alternative approach to the study of the BG that follows from consideration of a variety of clinical and experimental findings. The literature suggests that sensory aspects of BG functioning must be taken into account to fully appreciate the role of this system in motor control. A review of the literature concerning the latter suggests two points: The BG function as sensory analyzer for motor systems. That is, the BG convert sensory data from a form that is receptor oriented to a form that is relevant for guiding movement. The BG ultimately affect movement by gating sensory inputs into other motor areas rather than by directly affecting these areas. This sensory-based model of BG functioning explains a number of apparent discrepancies in the literature. In addition, seemingly anomalous findings are reconciled with the overwhelming evidence that the BG are a motor system. In particular, the suggestions of a BG role in attention and cognition are viewed as being intrinsic rather than orthogonal to the role of the BG in movement.

Animals↗
PubMed1982

Somatosensory properties of globus pallidus neurons in awake cats.

The somatosensory properties of globus pallidus (GP) neurons were assessed in awake restrained cats. Forty-two percent of GP units responded to stimulation of the face. Receptive fields were typically bilateral (49%) or contralateral and 75% included perioral tissues. Responsive units showed little ability to encode force. In contrast, cells were sensitive to changes in stimulus location within the receptive zone. The majority of cells so tested showed enhanced responding to stimuli applied within the perioral zone. Many (42%) of the cells which responded to brushing of the guard hairs or vibrissa were directionally sensitive. Of those, 89% showed enhanced responding to stimuli which moved toward the front of the mouth. These data were discussed in relation to a role of the GP in feedback regulated head positioning movements.

Animals↗
PubMed1981

Neural mechanisms of tardive dyskinesia.

Tardive dyskinesia is a disabling movement disorder, caused by antipsychotic medications, that occurs frequently and is not responsive to treatment. It is not known how the brain damage underlying tardive dyskinesia produces abnormal movement. We propose that altered sensory flow to motor systems results in this syndrome. Verification of such a mechanism could lead to early detection and improved treatment of tardive dyskinesia.

Brain↗
PubMed1981

Are movement disorders the most serious side effects of maintenance therapy with antipsychotic drugs?

This paper concerns assessment of the full range of risks associated with prolonged use of antipsychotic medication. It is generally accepted that the most common side effects of drug therapy involve motor problems. Movement disorders arise because antipsychotics, in a substantial proportion of patients, disrupt the basal ganglia. The basal ganglia, however, are involved in much more than simply motor control. Specifically, this neural system has been implicated in sensory reactivity, attention, memory, and cognition. It follows from this that antipsychotic drugs, in addition to causing motor problems, might also disrupt complex psychological processes.

Animals↗