EFFECT OF SEROTONIN SELECTIVE REUPTAKE INHIBITOR FLUOXETINE IN RETRIEVAL OF MEMORY TRACE IN RATS HAVING DIFFERENT SUSSCEPTIBILITY TO AUDIOGENIC SEIZURES
1University “Azad”, Tabriz, Islamic Republic of Iran.
2A.I.Karaev Institute of Physiology, NAS of Azerbaijan, Baku, Hismailova@azdata.net
The study concerns comparative analysis of retrieval of conditioned passive avoidance reaction (CPAR) under serotonin selective reuptake inhibitor – fluoxetin – (25 mg/kg into the stomach through guide 1 h prior to an experiment) in Wistar rats with different susceptibility to stressful acoustic stimulus and differing with inborn ratio of activities of brain serotoninergic (5-HT), noradrenergic (NA) and dopaminergic (DA) systems. The index of susceptibility to stressful stimulus was strength of seizure blow in rats. Differences in way of reaction to acoustic stress give grounds to cull animals into two groups: seizure-sensitive (SS – prone to seizures) and seizure-resistant (SR – without motor excitation) rats. Biochemical analysis of biogenic amines content in different brain structures demonstrated that SS rats differ originally with high levels of DA and 5-HT, whereas SR – with upregulation of NA and downregulation of 5-HT.
The experiments showed significant differences in maintaining memory traces on 2nd and 5th days after learning sessions in experimental and control animals of both groups. The SS control rats relatively to SR ones demonstrated increase of total time of staying in the safe compartment, exploratory activity as well as an increased number of rats kept memory trace. Acute administration of fluoxetine results in contrast effects in memory retrieval in the experimental animals of both groups. High scores of memory storage in all testing days on background of are noticed in SR rats in comparison to the controls in the form of increase of total time of animal staying in the light compartment when the increased exploratory activity is observed as well as in high percentage of rats kept memory trace. In the SS rats the mentioned parameters appear to decrease.
It is proposed that differences in retrieval of memory traces under fluoxetine in animals with different phenotypes are, apparently, due to intervention of the drug in 5-HT turnover changing inborn ratio of the brain 5-HT-ergic systems. Apparently, in the basis of mnestic processes lies different character of effect of serotonin upregulation on serotonin receptors having different level of expression in the nerve cells in the rats having different susceptibility to acoustic stress: upregulated – in SR and downregulated – in SS rats, which, perhaps, is related to significant original differences in serotonin level in the nerve cells of these groups of animals.