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Memory Enhancement by Bryostatin in Hermissenda

¹ Marine Biological Laboratory, Woods Hole, Massachusetts
² Blanchette Rockefeller Neuroscience Institute, Johns Hopkins University, Rockville, Maryland

Memory acquisition and information and behavioral recall are fundamental processes of great interest. Studies are being conducted in many model systems including marine molluscs like Aplysia californica and Hermissenda crassicornis.

Recently, the anti-cancer drug bryostatin has been found to enhance memory recall in rodent systems. Bryostatin is known to activate autophosphorylation of protein kinase-C (PKC), an enzyme implicated in memory formation. In Hermissenda, phosphorylated PKC activates calexcitin, a GTP/Ca²⁺-binding protein that triggers calcium release from internal stores while concurrently inhibiting two voltage-dependent outward K⁺ currents. The rise in internal Ca²⁺ coupled with a decrease in K⁺ currents is putatively responsible for the enhanced long-lasting depolarization (LLD) shown in Hermissenda type B-cell photoreceptors to be associated with memory acquisition.

Hermissenda can be trained and tested using a Pavlovian conditioning regime of light (CS) paired with agitation (US) (paired training event, TE). Previous studies have shown that two TEs produced short-term memory (STM) lasting 7 min. Nine TEs produced long-term memory (LTM; present at 60 min and lasting one day) that ultimately led to consolidated LTM (CLTM; present at 220 min and lasting up to 6 days). In this study, experimental animals exposed to low bryostatin concentrations (0.1–0.25 ng/ml) and two TEs (that normally evoke only STM) demonstrated the enhanced memory stage of LTM. Both four and six TEs (that normally do not generate LTM) tested positively for CLTM with bryostatin added. Nine TEs coupled with bryostatin at a high concentration (1.0 ng/ml), however, down-regulated memory acquisition; and the animals exhibited no conditioned response with CS testing. These findings will help elucidate knowledge about memory acquisition, storage, and retrieval; contribute information that can be used to answer fundamental questions pertaining to education and more effective teaching methods; and mediate memory-related pathologies like Alzheimer’s disease and other forms of dementia.

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				A. M. Kuzirian, H. T. Epstein, C. J. Gagliardi, T. J. Nelson, M. Sakakibara, C. Taylor, A. B. Scioletti, and D. L. Alkon Bryostatin Enhancement of Memory in Hermissenda Biol. Bull., June 1, 2006; 210(3): 201 - 214. [Abstract] [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Scioletti, A. B. Articles by Alkon, D. L. Search for Related Content PubMed Articles by Scioletti, A. B. Articles by Alkon, D. L.