Changes of locomotor, exploratory and emotional behavior in animal model of depression induced by deficiency of brain monoamine content.

The character of changes of open field behavior was not studied extensively in animal model of depression with deficiency of brain monoamine/serotonin content and obtained results are controversial. Both, enhancement and invariability of locomotor activity has been obtained. Additional investigation of this question is motivated also by insufficient study of exploratory and emotional behaviors in animal model of depression of this type. Animal model of depression was developed by chronic administration of Clomipramine and/or Melipramine in rat pups from postnatal day 7 (P7) and/or 14 (P14) to P21 and/or P28, respectively. Studies of open field behavior were started in adult age rats i.e. 8-12 weeks after the end of treatment. Control animals were the same age old. Two-week period of postnatal development starting at the P7 and/or P14 appeared equally sensitive to early antidepressant treatment. Modeled animals exhibited significant increase of horizontal locomotor activity. Frequency of center entrance and the time of staying in the center of open field were increased significantly indicating that animal models of depression can not percept really the level of stressfulness of novel surroundings. All of these changes indicate also to the significant level of exploratory behavior in modeled animals. Postnatal exposure of rat pups to Clomipramine or Melipramine produces significant increase of locomotor activity but dos not induces behavioral 'despair' or "refractory loss of interest" at mature age.

Nucleus- and species-specific properties of the slow (<1 Hz) sleep oscillation in thalamocortical neurons.

The slow (<1 Hz) rhythm is an electroencephalogram hallmark of resting sleep. In thalamocortical neurons this rhythm correlates with a slow (<1 Hz) oscillation comprising recurring UP and DOWN membrane potential states. Recently, we showed that metabotropic glutamate receptor activation brings about an intrinsic slow oscillation in thalamocortical neurons of the cat dorsal lateral geniculate nucleus in vitro which is identical to that observed in vivo. The aim of this study was to further assess the properties of this oscillation and compare them with those observed in thalamocortical neurons of three other thalamic nuclei in the cat (ventrobasal complex, medial geniculate body; ventral lateral nucleus) and two thalamic nuclei in rats and mice (lateral geniculate nucleus and ventrobasal complex). Slow oscillations were evident in all of these additional structures and shared several basic properties including, i) the stereotypical, rhythmic alternation between distinct UP and DOWN states with the UP state always commencing with a low-threshold Ca2+ potential, and ii) an inverse relationship between frequency and injected current so that slow oscillations always increase in frequency with hyperpolarization, often culminating in delta (delta) activity at approximately 1-4 Hz. However, beyond these common properties there were important differences in expression between different nuclei. Most notably, 44% of slow oscillations in the cat lateral geniculate nucleus possessed UP states that comprised sustained tonic firing and/or high-threshold bursting. In contrast, slow oscillations in cat ventrobasal complex, medial geniculate body and ventral lateral nucleus thalamocortical neurons exhibited such UP states in only 16%, 11% and 10% of cases, respectively, whereas slow oscillations in the lateral geniculate nucleus and ventrobasal complex of rats and mice did so in <12% of cases. Thus, the slow oscillation is a common feature of thalamocortical neurons that displays clear species- and nuclei-related differences. The potential functional significance of these results is discussed.