John D. Elsworth

Bio: John D. Elsworth is an academic researcher from Yale University. The author has contributed to research in topics: Dopamine & MPTP. The author has an hindex of 56, co-authored 163 publications receiving 10794 citations. Previous affiliations of John D. Elsworth include Rosalind Franklin University of Medicine and Science & University of Rochester.

Ghrelin modulates the activity and synaptic input organization of midbrain dopamine neurons while promoting appetite

Abstract: The gut hormone ghrelin targets the brain to promote food intake and adiposity. The ghrelin receptor growth hormone secretagogue 1 receptor (GHSR) is present in hypothalamic centers controlling energy metabolism as well as in the ventral tegmental area (VTA), a region important for motivational aspects of multiple behaviors, including feeding. Here we show that in mice and rats, ghrelin bound to neurons of the VTA, where it triggered increased dopamine neuronal activity, synapse formation, and dopamine turnover in the nucleus accumbens in a GHSR-dependent manner. Direct VTA administration of ghrelin also triggered feeding, while intra-VTA delivery of a selective GHSR antagonist blocked the orexigenic effect of circulating ghrelin and blunted rebound feeding following fasting. In addition, ghrelin- and GHSR-deficient mice showed attenuated feeding responses to restricted feeding schedules. Taken together, these data suggest that the mesolimbic reward circuitry is targeted by peripheral ghrelin to influence physiological mechanisms related to feeding.

Unilateral Transplantation of Human Fetal Mesencephalic Tissue into the Caudate Nucleus of Patients with Parkinson's Disease

Abstract: Background. Parkinson's disease is characterized by the loss of midbrain dopamine neurons that innervate the caudate and the putamen. Studies in animals suggest that fetal dopaminergic neurons can survive transplantation and restore neurologic function. This report compares the clinical results in four case patients with severe Parkinson's disease who underwent stereotaxic implantation of human fetal ventral mesencephalic tissue in one caudate nucleus with the results in a control group of similar subjects assigned at random to a one-year delay in surgery. Methods. Each case patient received cryopreserved tissue from one fetal cadaver (gestational age, 7 to 11 weeks). Before implantation, adjacent midbrain tissue underwent microbiologic, biochemical, and viability testing. Cyclosporine was administered for six months postoperatively. Results. The procedure was well tolerated. Three case patients showed bilateral improvement on motor tasks, as assessed on videotape, and were more functional in the...

Enduring Cognitive Deficits and Cortical Dopamine Dysfunction in Monkeys After Long-Term Administration of Phencyclidine

Abstract: The effects of the psychotomimetic drug phencyclidine on the neurochemistry and function of the prefrontal cortex in vervet monkeys were investigated. Monkeys treated with phencyclidine twice a day for 14 days displayed performance deficits on a task that was sensitive to prefrontal cortex function; the deficits were ameliorated by the atypical antipsychotic drug clozapine. Repeated exposure to phencyclidine caused a reduction in both basal and evoked dopamine utilization in the dorsolateral prefrontal cortex, a brain region that has long been associated with cognitive function. Behavioral deficits and decreased dopamine utilization remained after phencyclidine treatment was stopped, an indication that these effects were not simply due to direct drug effects. The data suggest that repeated administration of phencyclidine in monkeys may be useful for studying psychiatric disorders associated with cognitive dysfunction and dopamine hypofunction in the prefrontal cortex, particularly schizophrenia.

Behavioral improvement in a primate Parkinson's model is associated with multiple homeostatic effects of human neural stem cells

Abstract: Stem cells have been widely assumed to be capable of replacing lost or damaged cells in a number of diseases, including Parkinson's disease (PD), in which neurons of the substantia nigra (SN) die and fail to provide the neurotransmitter, dopamine (DA), to the striatum. We report that undifferentiated human neural stem cells (hNSCs) implanted into 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated Parkinsonian primates survived, migrated, and had a functional impact as assessed quantitatively by behavioral improvement in this DA-deficit model, in which Parkinsonian signs directly correlate to reduced DA levels. A small number of hNSC progeny differentiated into tyrosine hydroxylase (TH) and/or dopamine transporter (DAT) immunopositive cells, suggesting that the microenvironment within and around the lesioned adult host SN still permits development of a DA phenotype by responsive progenitor cells. A much larger number of hNSC-derived cells that did not express neuronal or DA markers was found arrayed along the persisting nigrostriatal path, juxtaposed with host cells. These hNSCs, which express DA-protective factors, were therefore well positioned to influence host TH+ cells and mediate other homeostatic adjustments, as reflected in a return to baseline endogenous neuronal number-to-size ratios, preservation of extant host nigrostriatal circuitry, and a normalizing effect on α-synuclein aggregation. We propose that multiple modes of reciprocal interaction between exogenous hNSCs and the pathological host milieu underlie the functional improvement observed in this model of PD.

Implications of normal brain development for the pathogenesis of schizophrenia

Abstract: • Recent research on schizophrenia has demonstrated that in this disorder the brain is not, strictly speaking, normal. The findings suggest that nonspecific histopathology exists in the limbic system, diencephalon, and prefrontal cortex, that the pathology occurs early in development, and that the causative process is inactive long before the diagnosis is made. If these findings are valid and not epiphenomena, then the pathogenesis of schizophrenia does not appear to fit either traditional metabolic, posttraumatic, or neurodegenerative models of adult mental illness. The data are more consistent with a neurodevelopmental model in which a fixed "lesion" from early in life interacts with normal brain maturational events that occur much later. Based on neuro-ontological principles and insights from animal research about normal brain development, it is proposed that the appearance of diagnostic symptoms is linked to the normal maturation of brain areas affected by the early developmental pathology, particularly the dorsolateral prefrontal cortex. The course of the illness and the importance of stress may be related to normal maturational aspects of dopaminergic neural systems, particularly those innervating prefrontal cortex. Some implications for future research and treatment are considered.

The neural basis of human error processing: Reinforcement learning, dopamine, and the error-related negativity.

Abstract: The authors present a unified account of 2 neural systems concerned with the development and expression of adaptive behaviors: a mesencephalic dopamine system for reinforcement learning and a “generic” error-processing system associated with the anterior cingulate cortex The existence of the error-processing system has been inferred from the error-related negativity (ERN), a component of the event-related brain potential elicited when human participants commit errors in reaction-time tasks The authors propose that the ERN is generated when a negative reinforcement learning signal is conveyed to the anterior cingulate cortex via the mesencephalic dopamine system and that this signal is used by the anterior cingulate cortex to modify performance on the task at hand They provide support for this proposal using both computational modeling and psychophysiological experimentation

Subanesthetic effects of the noncompetitive NMDA antagonist, ketamine, in humans: Psychotomimetic, perceptual, cognitive, and neuroendocrine responses.

Abstract: Background: To characterize further behavioral, cognitive, neuroendocrine, and physiological effects of subanesthetic doses of ketamine hydrochloride in healthy human subjects. Ketamine, a phencyclidine hydrochloride derivative, is a dissociative anesthetic and a noncompetitive antagonist of the N -methyl-D-aspartate subtype of excitatory amino acid receptor. Methods: Nineteen healthy subjects recruited by advertisements from the community participated in this randomized, double-blind, placebo-controlled study. Subjects completed three test days involving the 40-minute intravenous administration of placebo, ketamine hydrochloride (0.1 mg/kg), or ketamine hydrochloride (0.5 mg/kg). Behaviors associated with the positive and negative symptoms of schizophrenia were assessed by using the Brief Psychiatric Rating Scale. Changes in perception and behaviors associated with dissociative states were assessed by the Perceptual Aberration Subscale of the Wisconsin Psychosis Proneness Scale and the Clinician-Administered Dissociative States Scale. Cognitive function was assessed by using the (1) Mini-Mental State Examination; (2) tests sensitive to frontal cortical dysfunction, including a continuous performance vigilance task, a verbal fluency task, and the Wisconsin Card Sorting Test; and (3) tests of immediate and delayed recall. Plasma levels of cortisol, prolactin, homovanillic acid, and 3-methoxy-4-hydroxyphenethyleneglycol were measured. Results: Ketamine (1) produced behaviors similar to the positive and negative symptoms of schizophrenia; (2) elicited alterations in perception; (3) impaired performance on tests of vigilance, verbal fluency, and the Wisconsin Card Sorting Test; (4) evoked symptoms similar to dissociative states; and (5) preferentially disrupted delayed word recall, sparing immediate recall and postdistraction recall. Ketamine had no significant effect on the Mini-Mental State Examination at the doses studied. Ketamine also had no effect on plasma 3-methoxy-4hydroxyphenethyleneglycol levels, although it blunted a test day decline in plasma homovanillic acid levels at the higher dose. It also dose dependently increased plasma cortisol and prolactin levels. Ketamine produced small dose-dependent increases in blood pressure. Conclusions: These data indicate that N -methyl-Daspartate antagonists produce a broad range of symptoms, behaviors, and cognitive deficits that resemble aspects of endogenous psychoses, particularly schizophrenia and dissociative states.