18 It is also well-established that long-term potentiation (LTP) in the hippocampus is optimally elicited with priming
stimulations delivered at theta frequency (5-8 Hz) range, and its strength increases linearly with increasing theta power.19,20 Naturally occurring theta as well as LTP can induce synaptic changes of the type needed for memory storage.21 The implication of theta in learning and memory is further demonstrated by the findings that Inhibitors,research,lifescience,medical selective elimination or facilitation of theta activity blocks or enhances the induction of LTP and overall memory.22,23 Vertes and Kocsis24 proposed that “The theta rhythm acts as a significant signal. Information arriving with theta (with a particular phase) is stored in the hippocampus, whereas information arriving in the absence (or phase shift) of theta is not encoded.” Although the implication of sleep in learning and memory has long been advocated,25 there are Inhibitors,research,lifescience,medical as many studies that have failed to describe a link between sleep and memory as those that have claimed such
a relationship. Based on the convincing evidence that theta is directly involved in mnemonic functions of hippocampus,24 an important point is whether Inhibitors,research,lifescience,medical or not theta during active waking (exploratory behavior) and REM sleep serves the same function.26 We have shown that theta frequency during exploratory behavior selleckchem differed significantly from that during REM sleep,16 either because of behavioral differences between inbred Inhibitors,research,lifescience,medical strains during waking, or because theta is controlled by different genetic mechanisms
during sleep and waking. Because the link between theta and memory during sleep remains unknown and because theta is under strong genetic control, we believe that discovering its molecular basis could shed light on the theta rhythm function both during Inhibitors,research,lifescience,medical waking and sleep. The theta peak frequency (TPF) during REM sleep varies greatly with genetic background. The TPF is significantly different between C57BL/6J (B) and BALB/cByJ (C) inbred mice during REM sleep, the first being slow (5.756.25) while the second fast (6.75-7.75). Over 80% of the inter-inbred strain variability can be explained by genetic effects. In BXC Fl mice the TPF is similar to that of B and significantly faster than C, suggesting that the C allele is recessive. We have mapped a highly significant locus linked to TPF on the mouse chromosome 5, suggesting the presence of an autosomal recessive Megestrol Acetate gene. This single locus explained more than 65% of the variance. After narrowing down the identified region, different candidate genes were analyzed and the short-chain acyl-coenzyme A dehydrogenase gene (Acads) involved in the p-oxidation of short chain fatty acids, showed a spontaneous mutation in C mice. For comparison with REM theta, we have also analyzed TPF during waking episodes with clear theta activity (theta-dominated active waking).