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Preemptive Effect (preemptive + effect)

Distribution by Scientific Domains

Medical Sciences	75%

Selected Abstracts

Preemptive effect of nucleus of the solitary tract stimulation on amygdaloid kindling in freely moving cats

EPILEPSIA, Issue 3 2010
Victor M. Magdaleno-Madrigal
Summary Purpose:, The nucleus of the solitary tract (NTS) is a primary site where vagal afferents terminate. The aim of this study was to analyze the preemptive effect of NTS electrical stimulation on daily amygdaloid kindling (AK) in freely moving cats. Methods:, Seven adult male cats were used. Bipolar electrodes were stereotaxically implanted into both amygdalae, lateral geniculate bodies, hippocampi, and prefrontal cortices. In addition, a bipolar stainless steel electrode was implanted in the left NTS. Cats were recorded under the following experimental conditions: The NTS was stimulated for 6 days before the initiation of AK (1 min on/5 min off, 1 h total). AK was performed by stimulating the amygdala every 24 h (1 s, 60 Hz, 1 ms) until behavioral stage VI was reached. Results:, The number of stimulations to reach stage VI in control animals was 23.4 ± 3.7, in lateral tegmental field (LTF) animals was 17.0 ± 2.1 days. Animals subjected to preemptive NTS stimulation showed a significant increase (53.8 ± 5.9). In addition, behavioral development was retarded, with an increase in the number of stimulations required to reach stage III. In this group, overall kindling development was delayed, and amygdaloid afterdischarge duration did not show a progressive increase as was observed in the control group. Discussion:, Our results indicate that preemptive NTS electrical stimulation interferes with epileptogenesis. This anticonvulsive effect could be related to the activation of certain structures that inhibit seizure development. Therefore, results suggest that NTS mediates the anticonvulsive effect of vagus nerve stimulation. [source]

Coexistence in a metacommunity: the competition,colonization trade-off is not dead

ECOLOGY LETTERS, Issue 8 2006
V. Calcagno
Abstract The competition,colonization trade-off model is often used to explain the coexistence of species. Yet its applicability has been severely criticized, mainly because the original model assumed a strict competitive hierarchy of species and did not allow for any preemptive effect. We considered the impact of relaxing both of these limitations on coexistence. Relaxing trade-off intensity makes coexistence less likely and introduces a minimum colonization rate below which any coexistence is impossible. Allowing for preemption introduces a limit to dissimilarity between species. Surprisingly, preemption does not impede coexistence as one could presume from previous studies, but can actually increase the likelihood of coexistence. Its effect on coexistence depends on whether or not species in the regional pool are strongly limited in their colonization ability. Preemption is predicted to favour coexistence when: (i) species are not strongly limited in their colonization ability; and (ii) the competitive trade-off is not infinitely intense. [source]

Preemptive effect of nucleus of the solitary tract stimulation on amygdaloid kindling in freely moving cats

Effects of ketamine on formalin-induced activity in the spinal dorsal horn of spinal cord-transected cats: differences in response to intravenous ketamine administered before and after formalin

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 8 2000
H. Nagasaka
Background: Although formalin has been widely used as an algesic substance in rodent studies, the unique biphasic effect seen in rats is not present in humans. Humans, like cats, have a monophasic behavioral response to formalin injection. Electrophysiologically, spinal dorsal horn neurons in cats also have what could be considered a monophasic response after the initial burst of activity following formalin injection. Although several studies of the effects of ketamine on formalin responses have been carried out in rodents, we are unaware of similar studies in cats. We hypothesize that such species differences may explain observed differences in preemptive analgesic effects. Therefore, we examined the effects of ketamine on activity of spinal wide dynamic range (WDR) neurons evoked by formalin injection in cats. Methods: We investigated in cats the effect of ketamine on the activity of WDR neurons in the spinal dorsal horn that was evoked by formalin. In addition, we studied the effects of pre- and post-administration of ketamine on the maintained phase of the formalin response. Each dose was a subanesthetic, anesthetic or high anesthetic dose (3.0 mg · kg,1, 10 mg · kg,1, and 30 mg · kg,1). Results: Intravenously administered ketamine produced a dose-dependent depression of evoked activity that was significantly greater when the drug was administered before formalin. Conclusions: In spite of the species differences in responses to formalin, there still appears to be a clear preemptive effect of ketamine in the cat. Species differences may not explain apparent differences between human and animal preemptive analgesia. [source]