Positive Controls in Adults and Children Support That Very Few, If Any, New Neurons Are Born in the Adult Human Hippocampus.

Adult hippocampal neurogenesis was originally discovered in rodents. Subsequent studies identified the adult neural stem cells and found important links between adult neurogenesis and plasticity, behavior, and disease. However, whether new neurons are produced in the human dentate gyrus (DG) during healthy aging is still debated. We and others readily observe proliferating neural progenitors in the infant hippocampus near immature cells expressing doublecortin (DCX), but the number of such cells decreases in children and few, if any, are present in adults. Recent investigations using dual antigen retrieval find many cells stained by DCX antibodies in adult human DG. This has been interpreted as evidence for high rates of adult neurogenesis, even at older ages. However, most of these DCX-labeled cells have mature morphology. Furthermore, studies in the adult human DG have not found a germinal region containing dividing progenitor cells. In this Dual Perspectives article, we show that dual antigen retrieval is not required for the detection of DCX in multiple human brain regions of infants or adults. We review prior studies and present new data showing that DCX is not uniquely expressed by newly born neurons: DCX is present in adult amygdala, entorhinal and parahippocampal cortex neurons despite being absent in the neighboring DG. Analysis of available RNA-sequencing datasets supports the view that DG neurogenesis is rare or absent in the adult human brain. To resolve the conflicting interpretations in humans, it is necessary to identify and visualize dividing neuronal precursors or develop new methods to evaluate the age of a neuron at the single-cell level.

Istradefylline reduces memory deficits in aging mice with amyloid pathology.

Adenosine A2A receptors are putative therapeutic targets for neurological disorders. The adenosine A2A receptor antagonist istradefylline is approved in Japan for Parkinson's disease and is being tested in clinical trials for this condition elsewhere. A2A receptors on neurons and astrocytes may contribute to Alzheimer's disease (AD) by impairing memory. However, it is not known whether istradefylline enhances cognitive function in aging animals with AD-like amyloid plaque pathology. Here, we show that elevated levels of Aß, C-terminal fragments of the amyloid precursor protein (APP), or amyloid plaques, but not overexpression of APP per se, increase astrocytic A2A receptor levels in the hippocampus and neocortex of aging mice. Moreover, in amyloid plaque-bearing mice, low-dose istradefylline treatment enhanced spatial memory and habituation, supporting the conclusion that, within a well-defined dose range, A2A receptor blockers might help counteract memory problems in patients with Alzheimer's disease.

Barbiturate withdrawal following Internet purchase of Fioricet.

BACKGROUND: The Internet enables businesses to advertise their pharmaceutical products and services without medical supervision. The Internet also allows for the unsupervised purchase of medications that may have neurologic consequences. OBJECTIVE: To describe acute withdrawal delirium following the abrupt discontinuation of Fioricet. PATIENT: The patient was a 37-year-old woman with a history of depression and migraine headaches but not drug abuse. She developed a florid withdrawal delirium following the discontinuation of a drug she purchased online. The medication, which contained butalbital, was self-administered in escalating doses for the treatment of chronic headaches. Daily doses of up to 750 mg to 1000 mg were reported. RESULTS: The patient was admitted to the hospital for the treatment of unexplained seizures that were followed by several days of an intense withdrawal syndrome. Little improvement was noted after the administration of benzodiazepines and phenothiazine. After parenteral phenobarbital administration, her symptoms resolved. CONCLUSIONS: The withdrawal state from barbiturates is similar to that from ethanol. Tolerance can develop with prolonged abuse, leading to escalating drug doses to achieve the desired effect. The suggested management of both types of withdrawal syndromes is similar, but the relative resistance of the behavioral and autonomic features in patients was remarkable. Physicians should be aware of the ease with which medications can be purchased without supervision from Internet pharmacies. The magnitude of the number of drugs that are made available through this means creates a proclivity to withdrawal states.