Change in serotonin metabolism in the rat brain in response to the repeated stimulus presentation

The content of serotonin (5-HT), its metabolite 5-hydroxyindoleacetic acid (5-HIAA), monoamine oxidase (MAO) activity and kinetic parameters (K(m) and Vmax) for the reaction of 5-HT deamination, were examined in various regions of the rat brain after repeated presentation of a contextual stimulus. Habituation to the stimulus was accompanied by an increase of 5-HT metabolism and active transport of 5-HIAA in the amygdala, striatum and midbrain, while these changes were not found in the prefrontal cortex and hippocampus. Kinetic studies have revealed that the enhancement of 5-HT deamination by MAO in the brain structures was mediated by different catalytic mechanisms. A significant decrease in K(m) value for 5-HT deamination in the amygdala indicated an increase in the affinity of enzyme towards 5-HT. In the striatum the enhanced MAO activity was provided by increasing maximal rate of 5-HT deamination. It is concluded that an activation of presynaptic mechanisms of the serotonergic transmission in the amygdala and striatum is involved in the inhibition of biological significance and attention to repeated presentation of stimulus.     

On the taxonomy and presumable evolutionary pathways of planktonic larvae of Ceriantharia (Anthozoa,Cnidaria)

After investigation of the type specimens of 11 genera of ceriantharian larvae, it was concluded that the overwhelming majority of planktonic forms should be referred to the family Arachnactidae. Despite the fact that the presence of acontioids is traditionally considered as the only characteristic feature of this family, in most of the species acontioids develop at rather late ontogenetic stages. The importance of another feature, the presence or absence of p-rhabdoids, was considered. Members of suborder Penicillaria (Arachnactidae) typically have p-rhabdoids in the endoderm of alternate mesenteries and in acontioids. Members of suborder Spirularia (Cerianthidae and Botrucnidiferidae) have no p-rhabdoids and all cnidae in their mesenteries are restricted to the region of the mesenteric filament. In Arachnactidae the number of known larval forms significantly exceeds the number of benthic ones. The planktonic forms with developing and mature gonads were described in this family. The paedogenetic origin of Arachnactidae is discussed. It seems likely that, due to the uniformity and deficiency of definite morphological characteristics of the benthic members of the family Arachnactidae, only cnidom and type of the planktonic larva can be used for reliable taxonomical identification of the polyps.     

Role of serotonin receptors in the amygdaloid complex and central gray substance in conditioned passive avoidance reaction in rats

The functional role of 5-HT1 receptors in the memory trace retrieval was investigated in amygdala (AM), central gray substance of midbrain (CGS) and frontal cortex. There is used the passive avoidance response in the rat. The decrease of 5-HT1 binding sites in AM and CGS was revealed for the rats with retention of the passive avoidance response. The binding of 3H-5-HT in AM was found two sets of binding sites. It was concluded, that 5-HT1 receptors of AM and CGS are involved in learning processes either in the moment of the memory trace retrieval or immediately after it.     

Changes in brain monoamine oxidase activity in conditioned passive avoidance reaction in rats]

Activity of the enzyme monoamine oxidase (MAO) and kinetic parameters (Km, Vmax) for the 5-hydroxytryptamine (5-HT) and dopamine deamination were examined in the brain of rats with conditioned passive avoidance recall. Changes of the 5-HT and dopamine deamination were found in amygdala, striatum and frontal cortex. MAO activity was not changed in hippocampus. In amygdala the rate of 5-HT deamination was significantly increased and kinetic studies revealed increased affinity of the enzyme for 5-HT. The metabolism of dopamine in amygdala was unchanged. In frontal cortex the deamination of 5-HT was not changed, but the dopamine deamination significantly decreased. This decrease was due to lowering of MAO affinity for dopamine. In striatum the metabolism of both 5-HT and dopamine was reduced, and kinetic studies showed the lowering of Vmax for 5-HT and dopamine deamination.     

Distinctions in metabolism of serotonin and dopamine in rat brain during latent inhibition

Latent inhibition (LI) is a behavioral phenomenon, in which repeated presenting of a non-reinforced stimulus retards conditioning to this stimulus when it is coupled with a reinforcer. In order to find specific serotonin (5-HT- and dopamine (DA) changes mediating the LI, the 5-HT and DA metabolism was investigated in certain brain regions. Oxidative deamination of 5-HT and DA by monoamine oxidase (MAO) was determined in the prefrontal cortex, striatim, amygdala, and hippocampus at preexposure and testing stages of the LI using the passive avoidance procedure in rats. Preexposed animals demonstrated high MAO activity for 5-HT deamination in the amygdala and striatum and lower MAO activity for DA deamination in the amygdala and hippocampus. After testing the LI, a high level of 5-HT deamination by MAO was revealed in the amygdala, white the lower level of 5-HT deamination by MAO was shown in the prefrontal cortex. At the same time, no changes in DA metabolism were found in all the brain regions studied. Thus, the role of dopaminergic system in the LI effect may be limited by the preexposure stage. The obtained evidence suggests that the enhanced 5-HT activity in the amygdala and striatum induced by the preexposed stimulus is a principal biochemical mechanism underlying the LI.     

A neurophysiologic study of sleep in children during the first year of life]

Polygraphic investigation of day sleep has been carried out in thirty suckling infants (aged from 25 days to 12 months). EEG, OCG, SGR, respiration ECG, muscular activity, and in some infants, also rheographic parameters (REG and RG of the shin) have shown that already at an early nursing age, states of drowsiness, falling asleep, light and medium depth and deep slow sleep set in, as well as the so-called rapid sleep which occurs only after slow sleep. The denotation of the slow sleep stages is based on the classification by Loomis et al., though their electroenecepholographic expression in the infant is in many ways peculiar and undergoes certain dynamics during the first year of life. Peculiarities of the central area EEG have been exhibited in all the age groups, and it has been assumed that the central parts of the cortex of a suckling infant are a kind of "window" into the subcortical parts. While EEG, displaying new forms of activity at certain stages of sleep undergo distinct age changes, vegetative sleep manifestations display only some age depending quantitative differences. Thus, at the nursing age the mechanisms of electroencephalographic and vegetative sleep manifestations are of different degree of maturity: they possess a considerable autonomy, although they function in concord.     

The Probiotic Strain Lactobacillus fermentum 39: Biochemical Properties,Genomic Features,and Antiviral Activity

Microbiology - Lactobacillus fermentum 39 is a well-known probiotic strain, which is widely used for production of pharmacopoeial probiotic preparations, dietary supplements, and foodstuffs...     

Monoaminoxidase activity and serotonin metabolism in the brain of rats during latent inhibition]

The monoamine oxidase (MAO) activities and the concentrations of 5-HT and 5-hydroxyindoleacetic acid were investigated in four brain regions in rats during the acquisition of latent inhibition in one-trial passive avoidance task. 5-HT metabolism was not altered in the hippocampus. Changes of 5-HT metabolism were found in the frontal cortex during testing of latent inhibition and were accompanied by lowering of MAO activity. No change of 5-HT metabolism was observed in this structure at the stage of pre-exposition to conditioned stimulus. 5-HT metabolism was activated at the stage of pre-exposition to conditioned stimulus in the amygdala and striatum and was maintained on high level, in these structures during testing of latent inhibition. The data presented here indicate that serotoninergic system in various brains regions is specifically involved in the formation of different stages of latent inhibition.