(C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.”
“The mammalian circadian clock located in the suprachiasmatic nucleus (SCN) is thought to be modulated by 5-HT. 5-HT is though to inhibit photic phase shifts by inhibiting the release of glutamate from retinal terminals, as well as by decreasing the responsiveness of retinorecipient cells in the SCN. Furthermore, there is also evidence that 5-HT may underlie, in part, non-photic phase shifts of the circadian system. Understanding the mechanism by which 5-HT accomplishes these goals

is complicated by the wide variety of 5-HT receptors found in the SCN, the heterogeneous organization of both the circadian clock and the location of 5-HT receptors, and by a lack of

sufficiently selective pharmacological agents for the 5-HT receptors selleck products of interest. Genetically modified animals engineered to lack a specific 5-HT receptor present an alternative avenue Vadimezan of investigation to understand how 5-HT regulates the circadian system. Here we examine behavioral and molecular responses to both photic and nonphotic stimuli in mice lacking the 5-HT(1A) receptor. When compared with wild-type controls, these mice exhibit larger phase advances to a short late-night light pulse and larger delays to long 12 h light pulses that span the whole subjective night. Fos and mPer1 expression in the retinorecipient SCN is significantly attenuated following late-night light pulses in the 5-HT(1A) knockout animals. Finally, non-photic phase shifts to (+/-)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) are lost in the knockout animals, while attenuation of the phase shift to the PJ34 HCl long light pulse due to rebound activity following a wheel lock is unaffected. These findings suggest that the 5-HT(1A) receptor plays an inhibitory role in behavioral phase shifts, a facilitatory role in light-induced gene expression, a necessary role in phase shifts to

8-OH-DPAT, and is not necessary for activity-induced phase advances that oppose photic phase shifts to long light pulses. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.”
“In natural settings, the occurrence of unpredictable infrequent events is often associated with emotional reactions in the brain. Previous research suggested a special sensitivity of the brain to valence differences in emotionally negative stimuli. Thus, the present study hypothesizes that valence changes in infrequent negative stimuli would have differential effects on visual novelty processing. Event-related potentials (ERPs) were recorded for highly negative (HN), moderately negative (MN) and Neutral infrequent stimuli, and for the frequent standard stimulus while subjects performed a frequent/infrequent categorization task, irrespective of the emotional valence of the infrequent stimuli.