Effects of four non-cholinergic cognitive enhancers in comparison with tacrine and galanthamine on scopolamine-induced amnesia in rats

Abstract

Amnesia can be induced in rats in the passive avoidance paradigm by administration of scopolamine, a central muscarinic receptor antagonist. Tacrine or galanthamine, inhibitors of acetylcholinesterase, given in conjunction with scopolamine partially reversed the scopolamine-induced deficit in passive avoidance performance. Four so-called cognitive enhancers, all widely used for the treatment of the symptoms associated with mental aging, cerebral insufficiency and senile memory disorder, were investigated in this paradigm. Piracetam, an extract of Ginkgo biloba, dihydroergocristine and a combination of raubasine with dihydroergocristine, all attenuated the amnesia induced by scopolamine. In contrast, nicergoline had no significant effect. Raubasine alone also failed to significantly attenuate scopolamine-induced amnesia, although some doses of raubasine had a non-significant tendency (P less than 0.10) to reduce the amnesia.

Selective 5-HT1A Antagonists WAY 100635 and NAD-299 Attenuate the Impairment of Passive Avoidance Caused by Scopolamine in the Rat

“…In agreement with this view, tacrine and donepezil attenuated or completely blocked the inhibitory effects of scopolamine depending on the dose of the muscarinic receptor antagonist. It is clear, however, that noncompetitive AChE inhibitors including physostigmine and tacrine in general can only attenuate but not fully block the cognitive impairments caused by scopolamine in different learning and memory tasks (Chopin and Briley, 1992;Kojima et al, 1997;Rush and Streit, 1992;Yoshida and Suzuki, 1993). The more potent effect of tacrine compared to donepezil seen in this study might be because of differences in the mechanism of action of these two AChE inhibitors.…”

Characteristic Effects of Anti-dementia Drugs on Rat Sleep Patterns

“…Galantamine is reported to improve scopolamine-induced amnesia in rats at doses of 0.3 -3 mg/ kg (19). As for memantine, there are reports that the drug is effective in long-term spatial memory failure and amyloid β-induced memory impairment at a dose 5 -7.5 and 20 mg/kg, respectively (19,20).…”

“…2.0. The power spectrum densities, integrated and averaged, could be divided into 4 frequency areas: delta wave (0.5 -4 Hz), theta wave (4 -8 Hz), alpha wave (8 -13 Hz), and beta wave (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30). Delta activity (%) was calculated by the following equation: Delta activity (%) = delta wave power density in the drug administration period / delta wave power density in the vehicle administration period in each animal × 100.…”

The impact of flavonoids on spatial memory in rodents: from behaviour to underlying hippocampal mechanisms

“…Here, it is likely that the improved information recall in aged animals after 24 h is related to CA1 region synaptic plasticity as CA1 spatial representations are known to be less stable in aged animals compared to young ones [18,31,52,208]. In terms of the underlying pharmacological mechanisms, GBE has been reported to reduce levels of reactive oxygen species (ROS) [155,156], to increase cerebral blood flow [63], to modulate brain fluidity [204], to interact with the muscarinin cholinergic system [36] and to protect the striatal dopaminergic system [161]. Whatever the mechanism, it is likely that GBE bioactives are acting at various levels to enhance the memory system in order that it may transmit information more efficiently through hippocampal circuits.…”