Olfactory memory in rats, cholinergic agents and benzodiazepine receptor ligands

Vision, spatial cognition and intellectual disability

Vision is the most synthetic sensory channel and it provides specific information about the relative position of distant landmarks during visual exploration. In this paper we propose that visual exploration, as assessed by the recording of eye movements, offers an original method to analyze spatial cognition and to reveal alternative adaptation strategies in people with intellectual disabilities (ID). Our general assumption is that eye movement exploration may simultaneously reveal whether, why, and how, compensatory strategies point to specific difficulties related to neurological symptoms. An understanding of these strategies will also help in the development of optimal rehabilitation procedures.

Cognitive impairment and increased brain neurosteroids in adult rats perinatally exposed to low millimolar blood alcohol concentrations

Epidemiological evidence suggests that adolescents and adults perinatally exposed to alcohol, even at low doses, show high prevalence of cognitive impairment and social behavior deficits, which may be in part related to alcohol-induced changes of the gamma-aminobutyric acid (GABA)ergic neurotransmission. The endogenous neurosteroid 3alpha-hydroxy,5alpha-pregnan-20-one (3alpha,5alpha-tetrahydroprogesterone/3alpha,5alpha-THP), a potent positive allosteric modulator of GABA(A) receptor function, is implicated in the physiological tuning of GABA-mediated fast inhibition and in various alcohol's actions in the brain. This study was undertaken to determine whether perinatal exposure to low millimolar blood alcohol concentrations alters cognitive skills (social discrimination and inhibitory avoidance tests), emotional reactivity (elevated plus maze test), and neurosteroid content in brain cortex and hippocampus of adult male offspring. Dams had access to a 3% alcohol solution or to an equicaloric sucrose solution from gestational day 15 to postnatal day 9. Eighty-day old alcohol-exposed male offspring exhibited impaired social recognition memory, but unchanged inhibitory avoidance performance and normal behavior on the elevated-plus maze. The concentrations of 3alpha,5alpha-THP and its precursor progesterone were more than doubled in brain cortex and hippocampus of alcohol-exposed rats, whereas in plasma only progesterone was increased. Thus, exposure to low millimolar blood alcohol concentrations has a long-lasting impact on the developing brain as it causes an impairment of social recognition as well as an increase of brain neurosteroid content in mature animals. The latter may be consequent to altered expression/activity of brain steroidogenic enzymes, as reflected by the enduring increase of the GABA(A) receptor-active neurosteroid 3alpha,5alpha-THP in brain cortex and hippocampus, but not in plasma. It is speculated that, by inducing a greater amplification of GABA(A) receptor function, the elevation of 3alpha,5alpha-THP brain content contributes to the cognitive impairment exhibited by adult alcohol-exposed offspring.

The ameliorating effect of oroxylin A on scopolamine-induced memory impairment in mice

Oroxylin A is a flavonoid and was originally isolated from the root of Scutellaria baicalensis Georgi., one of the most important medicinal herbs in traditional Chinese medicine. The aim of this study was to investigate the ameliorating effects of oroxylin A on memory impairment using the passive avoidance test, the Y-maze test, and the Morris water maze test in mice. Drug-induced amnesia was induced by administering scopolamine (1 mg/kg, i.p.) or diazepam (1 mg/kg, i.p.). Oroxylin A (5 mg/kg) significantly reversed cognitive impairments in mice by passive avoidance and the Y-maze testing (P<.05). Oroxylin A also improved escape latencies in training trials and increased swimming times and distances within the target zone of the Morris water maze (P<.05). Moreover, the ameliorating effects of oroxylin A were antagonized by both muscimol and diazepam (0.25 mg/kg, i.p., respectively), which are GABA(A) receptor agonists. Furthermore, oroxylin A (100 microM) was found to inhibit GABA-induced inward Cl(-) current in a single cortical neuron. These results suggest that oroxylin A may be useful for the treatment of cognitive impairments induced by cholinergic dysfunction via the GABAergic nervous system.

Diazepam attenuates conditioned histamine release in guinea pigs

To clarify the possibility of pharmacological mediation on classical conditioning-associated asthmatic response, the effect of diazepam on an odor-induced conditioned histamine release was investigated in ovalbumin (OA)-sensitized guinea pigs, i.e. a model of bronchial asthma. The animals received conditioning sessions in which an antigen (OA) as the unconditioned stimulus and an odor (dimethylsulfide) as the conditioned stimulus (CS) were simultaneously inhaled. After the animals were intraperitoneally injected with saline or diazepam (2.5 or 5 mg/kg), they underwent exposure to the CS and blood collecting. This procedure was repeated three times in order that the animals would have each kind of injection. The animals injected with saline showed significantly higher levels of plasma histamine following the exposure to the CS as a conditioning effect compared with the baselines (P<0.05), whereas the group injected with diazepam (5 mg/kg) did not indicate such elevations. The suppressing effect of diazepam on the conditioned histamine release was also confirmed by a multiple regression analysis (5 mg/kg) and an analysis of covariance (2.5 and 5 mg/kg), even after adjustments for several factors regarding immunological sensitization and conditionability. The present study suggests that diazepam attenuates a conditioned histamine release.

Social memory is impaired in neonatally ibotenic acid lesioned rats

Postnatal lesion with ibotenic acid in the ventral hippocampus produces several behavioural effects that resemble the symptoms of schizophrenia. In the present study, we tested neonatally lesioned 1-year-old Sprague-Dawley rats for their social memory. It was found that social memory is worsened in lesioned rats. Subchronic treatment with haloperidol (0.025 mg/kg body weight) partly ameliorated this impairment. It was suggested that social memory might be a useful paradigm to test clinically used and potential antipsychotic drugs for their effects on learning and memory processes.