MODULATION OF DEFENSIVE REFLEX CONDITIONING IN SNAILS BY SEROTONIN

We studied the role of serotonin in the mechanisms of learning in terrestrial snails. To produce a serotonin deficit, the neurotoxic analogues of serotonin, 5,6- or 5,7-dihydroxytryptamine (5,6/5,7-DHT) were used. Injection of 5,6/5,7-DHT was found to disrupt defensive reflex conditioning. Within two weeks of neurotoxin application, the ability to learn had recovered. Daily injection of serotonin before a training session accelerated defensive reflex conditioning and daily injections of 5-HTP in snails with a deficiency of serotonin induced by 5,7-DHT restored the snail’s ability to learn. We discovered that injections of the neurotoxins 5,6/5,7-DHT as well as serotonin, caused a decrease in the resting and threshold potentials of the premotor interneurons LPa3 and RPa3

Participation of NO-synthase in Control of Nitric Oxide Level in Rat Hippocampus after Modelling of Ischaemic and Haemorrhagic Insult

Electron paramagnetic resonance (EPR) was used as a method for recording the content of the nitric oxide (NO) in hippocampal tissues of intact rats and rats after modelling of ischaemic and haemorrhagic stroke. Based on direct measurements of NO by EPR spectroscopy, it was shown that, within 5 hours after the onset of symptoms of ischaemic and haemorrhagic stroke, the formation of NO in the hippocampus was reduced by a factor of 2-3 and this reduction was maintained for a period of between 24 and 72 hours. The results show that a systemic character of a decrease in the intensity of NO production during the modelling of ischaemic events in the brain reflects the effects of central dysregulation of the functions at the level of the whole organism such that it is appropriate to consider implementing the correction of the vital systems of the body in a stroke. It has indicated that non-selective NO-synthase blocker L-NAME reduced the low level of NO production by a factor of 3 by its administration within 72 hours after post-ischaemic and haemorrhagic stroke. It was discovered however that L-NAME returns the level of NO production to baseline (control) by its administration within 5 hours after ischaemia