Biochemical, electrophysiological, and pharmacological evidence supporting a role for cholinergic dysfunction in age-related memory disturbances is critically reviewed. An attempt has been made to identify pseudoissues, resolve certain controversies, and clarify misconceptions that have occurred in the literature. Significant cholinergic dysfunctions occur in the aged and demented central nervous system, relationships between these changes and loss of memory exist, similar memory deficits can be artificially induced by blocking cholinergic mechanisms in young subjects, and under certain tightly controlled conditions reliable memory improvements in aged subjects can be achieved after cholinergic stimulation. Conventional attempts to reduce memory impairments in clinical trials hav not been therapeutically successful, however. Possible explanations for these disappointments are given and directions for future laboratory and clinical studies are suggested.

Benzodiazepines remain widely used for the treatment of anxiety disorders despite prominent, often limiting side effects including sedation, muscle relaxation, and ataxia. A compound producing a robust anxiolytic action comparable to benzodiazepines, but lacking these limiting side effects at therapeutic doses (an anxioselective agent), would represent an important advance in the treatment of generalized anxiety disorder, and perhaps other anxiety disorders. Here we report that the pyrazolo[1,5-a]-pyrimidine, ocinaplon, exhibits an anxioselective profile in both preclinical procedures and in patients with generalized anxiety disorder, the most common of the anxiety disorders. In rats, ocinaplon produces significant muscle relaxation, ataxia, and sedation only at doses >25-fold higher than the minimum effective dose (3.1 mg͞kg) in the Vogel ''conflict'' test. This anticonflict effect is blocked by flumazenil (Ro 15-1788), indicating that like benzodiazepines, ocinaplon produces an anxiolytic action through allosteric modulation of GABA A receptors. Nonetheless, in eight recombinant GABAA receptor isoforms expressed in Xenopus oocytes, the potency and efficacy of ocinaplon to potentiate GABA responses varied with subunit composition not only in an absolute sense, but also relative to the prototypical benzodiazepine, diazepam. In a double blind, placebo controlled clinical trial, a 2-week regimen of ocinaplon (total daily dose of 180 -240 mg) produced statistically significant reductions in the Hamilton rating scale for anxiety scores. In this study, the incidence of benzodiazepine-like side effects (e.g., sedation, dizziness) in ocinaplon-treated patients did not differ from placebo. These findings indicate that ocinaplon represents a unique approach both for the treatment and understanding of anxiety disorders.generalized anxiety disorder ͉ benzodiazepines

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