|
|
Effect of ketamine on light-induced changes in the circadian system
Kratina, Alex ; Bendová, Zdeňka (advisor) ; Valeš, Karel (referee)
The circadian system is controlled by the suprachiasmatic nuclei of the hypothalamus (SCN) and ensures optimal timing of physiological processes. Synchronization of this system with external light conditions is based on the activation of NMDA receptors during light exposure in the subjective night. Ketamine is a non-competitive antagonist of NMDA receptors used as a safe anesthetic, whose subanesthetic doses act as an antidepressant with a rapid onset of action, and increase proliferation in some parts of the brain. There are hypotheses about the possible effect of subanesthetic doses of ketamine on the circadian system, altough this effect has not yet been tested. This work aims to investigate the effect of a single subanesthetic dose of ketamine on the circadian system of the rat, especially on light-induced changes in locomotor activity and light-induced markers in the SCN and dentate gyrus, which represents one of the strongly proliferative areas of the brain. Our results show that ketamine decreases light pulse-induced c-FOS protein expression in the SCN at the onset of the subjective night, but increases this expression in the dentate gyrus under the same conditions. Reduction of c-FOS expression in the SCN correlates with the behavioral output of the circadian system and thus suppresses the...
|
|
|
Investigation of the involvement of central ghrelin signalling in methamphetamine dependence using behavioural and molecular methods
Lapka, Marek ; Šustková, Magdaléna (advisor) ; Votava, Martin (referee) ; Amchová, Petra (referee)
v anglickém jazyce Interest in appetite-inducing peptide hormones, such as ghrelin, is gradually increasing. There is a growing number of publications dealing with the involvement of this orexigenic peptide in the mechanisms of obesity and various addictive behaviours, not excluding addiction to stimulant substances including methamphetamine. Central ghrelin signaling appears to play an important role in addictive behavior, and in the processing of memory traces. Recently, antagonism of the ghrelin receptor for growth hormone secretion (GHS-R1A) has been proposed as a promising tool for the still unsatisfactory treatment of methamphetamine addiction. Premedication with a commonly used experimental GHS-R1A antagonist, the triazole derivative, JMV2959, significantly reduced the rewarding and reinforcing effects of methamphetamine in several animal models of addiction. However, the molecular aspects of GHS-R1A involvement in specific brain regions related to the addiction process remain unclear. This work demonstrates that acute and subchronic (4 days) administration of JMV2959 alone, at doses significantly effective in addiction models (1 and 3 mg/kg intraperitoneally), had no effect on memory functions tested in the Morris water maze in rats, as well as no significant effects on molecular markers...
|
|
|
Synchronization of circadian system during prenatal and early postnatal development
Houdek, Pavel ; Sumová, Alena (advisor) ; Novotná, Růžena (referee)
One of the few attributes common to almost all living organisms is an ability to generate and maintain endogenous rhythms, which are controlled by a biological clock. The processes, which recur with a period of about 24 hours, are known as the circadian rhythms. The circadian clock controls rhythms of molecular, physiological as well as behavioral processes and adapts their activity to regularly appearing changes in day and night or season. In case of mammals, central oscillator is located in the hypothalamic suprachiasmatic nuclei (SCN). The SCN clock entrains rhythms of peripheral oscillators located in cells of other tissues. The central oscillator itself is synchronized with external environment mainly by a light-dark cycle, however, other cues can entrain the SCN clock as well. For example, during prenatal development, entrainment of a fetal clock is entirely dependent on non-photic cues derived from maternal organism. This study aimed to investigate a mechanism of the communication between the maternal and fetal central oscillators. A hypothesis was tested whether maternal melatonin may play a role in entrainment of the circadian clock in the fetal SCN. Furthermore, a mechanism, how melatonin may entrain the fetal clock was investigated at molecular level. The results provided evidence, that...
|
|
|
The effect of endocannabinoid system on light entrainment of rat circadian system
Filipovská, Eva ; Bendová, Zdeňka (advisor) ; Balík, Aleš (referee)
Circadian system of mammals is generated in suprachiasmatic nuclei of hypothalamus. This system is synchronized with light conditions through phase shifts that occur after light exposition during the subjective night. Recent studies have shown that activation of endocannabinoid receptors attenuates the light-induced phase shifts and influences the ability of circadian system to light entrainment. The aim of this work is to examine this influence on behavioral level and on light-reactive cellular processes within the suprachiasmatic nuclei. Our results show that the activation of endocannabinoid system via CB1 receptor agonist modulates the light-induced phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and the expression of c-Fos protein in neurons of suprachiasmatic nuclei in the rat's brain; these cellular processes correlate with the attenuation of light entrainment. Keywords: circadian system, suprachiasmatic nuclei, light entrainment, endocannabinoid system, CB1 receptors, extracellular signal-regulated kinase 1/2, ERK1/2, c-Fos
|
|
|
Synchronization of circadian system during prenatal and early postnatal development
Houdek, Pavel ; Sumová, Alena (advisor) ; Novotná, Růžena (referee)
One of the few attributes common to almost all living organisms is an ability to generate and maintain endogenous rhythms, which are controlled by a biological clock. The processes, which recur with a period of about 24 hours, are known as the circadian rhythms. The circadian clock controls rhythms of molecular, physiological as well as behavioral processes and adapts their activity to regularly appearing changes in day and night or season. In case of mammals, central oscillator is located in the hypothalamic suprachiasmatic nuclei (SCN). The SCN clock entrains rhythms of peripheral oscillators located in cells of other tissues. The central oscillator itself is synchronized with external environment mainly by a light-dark cycle, however, other cues can entrain the SCN clock as well. For example, during prenatal development, entrainment of a fetal clock is entirely dependent on non-photic cues derived from maternal organism. This study aimed to investigate a mechanism of the communication between the maternal and fetal central oscillators. A hypothesis was tested whether maternal melatonin may play a role in entrainment of the circadian clock in the fetal SCN. Furthermore, a mechanism, how melatonin may entrain the fetal clock was investigated at molecular level. The results provided evidence, that...
|
guest ::
