Reversal of anisomycin-induced amnesia by the ergot derivative hydergine

Post-translational protein modification as the substrate for long-lasting memory

Prevailing models of memory identify mRNA translation as necessary for long-lasting information storage. However, there are enough instances of memory storage in the virtual absence of protein synthesis to prompt consideration of alternative models. A comprehensive review of the protein synthesis literature leads us to conclude that the translational mechanism is exclusively a permissive, replenishment step. Therefore, we propose that post-translational modification (PTM) of proteins already at the synapse is the crucial instructive mechanism underlying long-lasting memory. A novel feature of this model is that non-random spontaneous (or endogenous) brain activity operates as a regulated positive-feedback rehearsal mechanism, updating network configurations by fine-tuning the PTM state of previously modified proteins. Synapses participating in memory storage are therefore supple, a feature required for networks to alter complexity and update continuously. In analogy with codons for amino acids, a long-lasting memory is represented by a 'degenerate code' - a set of pseudo-redundant networks that can ensure its longevity.

Vinpocetine: nootropic effects on scopolamine-induced and hypoxia-induced retrieval deficits of a step-through passive avoidance response in rats

Vinpocetine, vincamine, aniracetam, and Hydergine, compounds with purported cognition activating activity, were evaluated for their ability to prevent scopolamine-induced and hypoxia-induced impairment of passive avoidance retention (24 hr) in rats. Vinpocetine (peak effect dose [PED]= 200 mg/kg PO), aniracetam (PED = 100 mg/kg PO), vincamine (PED = 30 mg/kg PO), and Hydergine (PED = 1 mg/kg PO) prevented memory disruption by scopolamine. Vinpocetine (PED = 3 mg/kg PO) and aniracetam (PED = 30 mg/kg PO) were also effective in preventing disruption of passive avoidance retention impaired by 7% oxygen hypoxia. In contrast, Hydergine (0.05 to 3 mg/kg PO) and vincamine (0.3 to 100 mg/kg PO) were not effective against hypoxia-induced impairment. Hydergine at doses greater than 10 mg/kg PO markedly impaired motor function. In both tests the protection was dose-related for all test substances in an inverted U-shaped manner. Mecamylamine (1, 3, 10 mg/kg SC), (-)-nicotine (0.1 to 0.4 mg/kg SC), apovincaminic acid (1-400 mg/kg PO) and pemoline (1-100 mg/kg PO) did not protect against memory impairment induced by either procedure. These data support the view that vinpocetine, a compound chemically distinct from the pyrrolidinones, has a cognitive activating ability as defined in models of both scopolamine-induced and hypoxia-induced memory impairment in rats.

Habituation of exploratory activity in mice: a screening test for memory enhancing drugs

The habituation of exploratory activity was investigated as an experimental model of memory processes. Mice were given two sessions in a simple photo-cell activity cage and the decrease in activity at the second session (habituation) served as an index of retention. Retention decreased as the interval between sessions increased from 1 to 7 days. Retention was facilitated or impaired by post-session. IP injections of several drugs known respectively to improve [(+)-amphetamine, nicotine, physostigmine, strychnine] or impair (chlordiazepoxide, chlorpromazine, scopolamine) memory in other animal models. Memory facilitation or impairment only occurred if administration of the enhancing or impairing agent closely followed the first session, suggesting that the consolidation period was of limited duration. Post-session administration of presumably rewarding or noxious stimuli did not affect retention. Finally, retention was enhanced by several drugs which are used clinically for the treatment of memory disorders (bromocriptine, dihydroergotoxine, meclofenoxate, naftidrofuryl and piracetam). These results, consistent with classical learning data, suggest that habituation of exploratory activity in mice provides a simple but valid model of memory processes suitable for the screening of memory enhancing drugs.