Ototoxicity: a high risk to auditory function that needs to be monitored in drug development.

Hearing loss constitutes a major global health concern impacting approximately 1.5 billion people worldwide. Its incidence is undergoing a substantial surge with some projecting that by 2050, a quarter of the global population will experience varying degrees of hearing deficiency.

Scopolamine induced deficits in a battery of rat cognitive tests: comparisons of sensitivity and specificity.

Despite much research, the cognitive effects of scopolamine hydrobromide, a cholinergic antagonist, remain controversial. Scopolamine affects multiple systems each of which can impact behavior. One way to tease apart the effects of the drug is to determine the effects of low scopolamine doses on different abilities.

Donepezil primarily attenuates scopolamine-induced deficits in psychomotor function, with moderate effects on simple conditioning and attention, and small effects on working memory and spatial mapping.

Rationale: Alzheimer's dementia (AD) patients have profound deficits in cognitive and social functions, mediated in part by a decline in cholinergic function. Acetylcholinesterase inhibitors (AChEI) are the most commonly prescribed treatment for the cognitive deficits in AD patients, but their therapeutic effects are small, and it is still not clear if they primarily affect attention, memory, or some other cognitive/behavioral functions.

Objectives: The objective of the present experiments was to explore the effects of donepezil (Aricepttrade mark), an AChEI, on behavioral deficits related exclusively to cholinergic dysfunction.

Soluble Abeta and cognitive function in aged F-344 rats and Tg2576 mice.

Recent findings suggest that Alzheimer's dementia may be mediated by soluble beta amyloid (Abeta) more than the deposits of aggregated, insoluble Abeta, and vulnerability to cognitive deficits after scopolamine challenge may help identify AD even in patients that are still pre-symptomatic. The objectives of the present experiments were to determine if vulnerability to cognitive deficits after scopolamine challenge is related to levels of soluble Abeta, and if levels of soluble Abeta are more closely related to cognitive deficits than levels of insoluble Abeta, even in aged, transgenic mice, after they have developed very high levels of insoluble Abeta. Aged F-344 rats and young mice over-expressing the Swedish mutation in the human amyloid precursor protein (APPsw; Tg2576+) had elevated levels of soluble Abeta, and were more vulnerable to scopolamine challenge in the Morris water maze (MWM), relative to young rats and Tg2576- mice; but, among individual animals, higher levels of soluble Abeta were not correlated with vulnerability to scopolamine.

Effects of CRF1 receptor antagonists and benzodiazepines in the Morris water maze and delayed non-matching to position tests.

Rationale: Benzodiazepines continue to be widely used for the treatment of anxiety, but it is well known that benzodiazepines have undesirable side effects, including sedation, ataxia, cognitive deficits and the risk of addiction and abuse. CRF(1) receptor antagonists are being developed as potential novel anxiolytics, but while CRF(1) receptor antagonists seem to have a better side-effect profile than benzodiazepines with respect to sedation and ataxia, the effects of CRF(1) receptor antagonists on cognitive function have not been well characterized. It is somewhat surprising that the potential cognitive effects of CRF(1) receptor antagonists have not been more fully characterized since there is some evidence to suggest that these compounds may impair cognitive function.

Chronobiotic activity of N-[2-(2,7-dimethoxyfluoren-9-yl)ethyl]-propanamide. Synthesis and melatonergic pharmacology of fluoren-9-ylethyl amides.

A series of fluoren-9-yl ethyl amides (2) were synthesized and evaluated for human melatonin MT(1) and MT(2) receptor binding. N-[2-(2,7-dimethoxyfluoren-9-yl)ethyl]propanamide (2b) was selected and evaluated in functional assays measuring intrinsic activity at the human MT(1) and MT(2) receptors and demonstrated full agonism at both receptors. The chronobiotic properties of 2b were demonstrated in both acute and chronic rat models where 2b produced an acute phase advance of 32 min at 1mg/kg and chronically entrained free-running rats with a mean effective dose of 0.

Heterocyclic aminopyrrolidine derivatives as melatoninergic agents.

A series of chiral heterocyclic aminopyrrolidine derivatives was synthesized as novel melatoninergic ligands. Binding affinity assays were performed on cloned human MT(1) and MT(2) receptors, stably expressed in NIH3T3 cells. Compound 16 was identified as an orally bioavailable agonist at MT(1) and MT(2) melatonin receptors with low vasoconstrictive activity.

An assessment of the effects of serotonin 6 (5-HT6) receptor antagonists in rodent models of learning.

Antagonists of serotonin 6 (5-HT6) receptors have been reported to enhance cognition in animal models of learning, although this finding has not been universal. We have assessed the therapeutic potential of the specific 5-HT6 receptor antagonists 4-amino-N-(2,6-bis-methylamino-pyrimidin-4-yl)-benzenesulfonamide (Ro 04-6790) and 5-chloro-N-(4-methoxy-3-piperazin-1-yl-phenyl)-3-methyl-2-benzothiophenesulfonamide (SB-271046) in rodent models of cognitive function. Although mice express the 5-HT6 receptor and the function of this receptor has been investigated in mice, all reports of activity with 5-HT6 receptor antagonists have used rat models.

Indanyl piperazines as melatonergic MT2 selective agents.

Optimization of a benzyl piperazine pharmacophore produced N-acyl-4-indanyl-piperazines that bind with high affinity to melatonergic MT(2) receptors. (R)-4-(2,3-dihydro-6-methoxy-1H-inden-1-yl)-N-ethyl-1-piperazine-carboxamide fumarate (13) is a water soluble, selective MT(2) agonist, which produces advances in circadian phase in rats at doses of 1-56 mg/kg that are no different from those of melatonin at 1 mg/kg. Unlike melatonin, 13 produced only weak contractile effects in rat tail artery.