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1 October 2016 Effects of Caffeine on Olfactory Learning in Crickets
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Abstract

Caffeine is a plant-derived alkaloid that is generally known as a central nervous system (CNS) stimulant. In order to examine the effects of caffeine on higher CNS functions in insects, we used an appetitive olfactory learning paradigm for the cricket Gryllus bimaculatus. Crickets can form significant long-term memories (LTMs) after repetitive training sessions, during which they associate a conditioned stimulus (CS: odor) with an unconditioned stimulus (US: reward). Administration of hemolymphal injections of caffeine established LTM after only single-trial conditioning over a wide range of caffeine dosages (1.6 µµg/kg to 39 mg/kg). We investigated the physiological mechanisms underlying this enhancement of olfactory learning performance pharmacologically, focusing on three major physiological roles of caffeine: 1) inhibition of phosphodiesterase (PDE), 2) agonism of ryanodine receptors, and 3) antagonism of adenosine receptors. Application of drugs relevant to these actions resulted in significant effects on LTM formation. These results suggest that externally applied caffeine enhances LTM formation in insect olfactory learning via multiple cellular mechanisms.

© 2016 Zoological Society of Japan
Seigo Sugimachi, Yukihisa Matsumoto, Makoto Mizunami, and Jiro Okada "Effects of Caffeine on Olfactory Learning in Crickets," Zoological Science 33(5), 513-519, (1 October 2016). https://doi.org/10.2108/zs150209
Received: 23 December 2015; Accepted: 1 April 2016; Published: 1 October 2016
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