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Expectation of an important event affects responses to irrelevant stimuli of different modalities

100%

Michalski A.

tom 60

nr 4

Periodic alterations of event-related potentials (ERPs) were studied during "oddball" tasks. Sequences of randomly intermixed frequent (non-target) and rare (target) stimuli were presented. In visual experiments, these were flashes of light of two different colors. In auditory tests there were two tones of different frequencies. The instruction was to keep a mental count of each target stimulus. To study the alterations of the "state of the brain" produced by target detection, responses to non-targets immediately following targets were compared with responses to an eighth subsequent non-target stimulus. To evaluate the effect of such "brain states" on responses to stimuli of a different modality, additional visual stimuli (probes) were delivered after both auditory and visual "oddball" stimuli. It was found that responses to the eighth presentation of non-target stimulus were preceded by significant negative shift of recorded potential. This shift was smaller before the responses to non-targets immediately following the presentation of target stimuli. The difference was significant both in auditory and visual tests. Responses to "oddball" stimuli were little affected: only the reduction of P200 peaks in "after target" responses was significant in visual tests. Responses to probes showed stronger effects: when visual probes followed visual "oddball" stimuli, all three components measured (N100, P130 and P200) were shifted positively in responses to eighth presentations of non-targets. When visual probes were presented in auditory tests, only the amplitude of the N100 component was significantly affected.

Eliot Stellar [1919-1993]

100%

Fonberg E. , Zagrodzka J.

tom 54

nr 1

Cyclic GMP metabolism and its role in brain physiology

84%

Domek-Lopacinska K. , Strosznajder J. B.

Journal of Physiology and Pharmacology. Supplement

2005

tom 56

nr 2

15-34

Cyclic GMP (cGMP) is synthesized by guanylyl cyclase (GC) in response to nitric oxide (NO) and carbon monoxide (CO) or natiuretic peptides (NPs); atrial, brain and C-type (ANP, BNP and CNP). cGMP is degraded by several cGMP-specific phosphodiesterases (PDEs). Guanylate cyclases (GC) are differentiated into: membrane-bound/particulate (pGC) and cytosolic/soluble (sGC). In recent years evidence has accumulated that NO is the main activator of sGC and NO/cGMP plays important role in glutaminergic, cholinergic and dopaminergic signaling pathways. cGMP in the nervous system is involved in long term potentiation and depression (LTP, LTD) suggesting its participation in learning and memory mechanism. cGMP regulates calcium homeostasis and phototransduction. Its level is regulated by PDEs and their specific inhibitors protect cGMP level in cells and are very important from clinical point of view.

Effect of aging and oxidative-genotoxic stress on poly[ADP-ribose] polymerase-1 activity in rat brain

67%

Strosznajder R. P. , Jesko H. , Adamczyk A.

nr 4

Poly(ADP-ribose) polymerase-1 (PARP-1, EC 2.4.2.30), a DNA-bound enzyme, plays a key role in genome stability, but after overactivation can also be responsible for cell death. The aim of the present study was to investigate PARP-1 activity in the hippocampus, brain cortex, striatum and cerebellum in adult (4 months) and aged (24 months) specific pathogen free Wistar rats and to correlate it with PARP-1 protein level and p53 expression. Moreover, the response of PARP-1 in adult and aged hippocampus to oxidative/genotoxic stress was evaluated. Our data indicated a statistically significant enhancement of PARP-1 activity in aged hippocampus and cerebral cortex comparing to adults without statistically significant changes in PARP-1 protein level. The expression of p53 mRNA was elevated in all aged brain parts with the exception of the cerebral cortex. Our data suggest that enhancement of PARP-1 activity and p53 expression in aged brain may indicate higher DNA damage. Our data also indicate that during excessive oxidative/genotoxic stress there is no response of PARP-1 activity in aged hippocampus in contrast to a significant enhancement of PARP-1 activity in adults which may have important consequences for the physiology and pathology of the brain.