Effect of whole-body exposure to high-frequency electromagnetic field on the brain electrogeny in neurodefective and healthy mice.

A direct registration of brain cortical and hippocampal activity during a high-frequency electromagnetic field (HF EMF) exposure was performed. All experimental procedures were done under urethane anaesthesia (20%, 2 g/kg i.p.) in Lurcher mutant mice, wild type (healthy littermates) were used as controls. Experimental animals were exposed to the HF EMF with frequency corresponding to cellular phones. Our method is based on the use of gel electrodes (silicon tubes or glass microcapillaries filled with agar) where the connection with classical electrodes is located out of HF EMF space. ECoG evaluation showed a distinct shift to lower frequency components but clear effect has been observed only in wild type (healthy) mice whereas in Lurcher mutant mice only gentle differences between frequency spectra were found. Measurement of hippocampal rhythmicity showed gentle changes with increase of higher frequencies (i.e. opposite effect than in cortex) and changes in theta oscillations registered from a dentate gyrus and CA1 area in both types of animals (healthy and mutant). These findings support the idea about possible influencing the central nervous system by HF EMF exposure and support also some recent results about possible health risks resulting from cellular phones use.

Interactions between nitric oxide and dopamine in inhibitory learning and memory in newborn rats.

Taking into account our previous results on dopamine and nitric oxide effects on neonatal inhibitory learning and memory in rats, the mutual interactions of the two molecules were studied in this experimental paradigm. Both increased dopamine content and nitric oxide bioavailability in the brain after application of dopamine and L-arginine as substrate for nitric oxide synthase solutions into lateral cerebral ventricles improved learning and 24 h memory. Joint application of dopamine and L-arginine yielded still more improvement. Learning and memory processing were dose dependently enhanced by D1 receptor agonists as well, whereas D1 receptor antagonists had an opposite and also dose-dependent effect. Dopamine or D1 receptor agonists administered together with nitro-L-arginine, a nitric oxide synthase inhibitor that impaired learning and memory due to a decreased nitric oxide availability, antagonized the effect of nitro-L-arginine, as did L-arginine. D1 receptor antagonists impaired both learning and memory, and L-arginine rendered learning values normal. The dopamine and D1 receptor-agonist effect on 24 h memory was concentration dependent, and their higher concentrations substantially increased the retention indexes. The intimate mechanisms of these interactions are to be identified in further experiments.

Inhibitory learning and memory in newborn rats influenced by nitric oxide.

The impact of nitric oxide on learning, memory processing and retrieval was studied in the neonatal rats. For comparison, spontaneous motor activity and changes of brain temperature were also studied after nitric oxide manipulations in identical age groups. The nitric oxide availability was either increased by a systemic or intracerebroventricular application of L-arginine, a substrate of nitric-oxide synthase, or decreased by nitro-L-arginine, its inhibitor. L-arginine, 20 mM or nitro-L-arginine, 10 or 5 mM were given intraperitoneally, 1 ml/100 g weight, or in the amounts of 11 into both lateral cerebral ventricles. Intact and saline injected pups were used as controls. Spontaneous motor behavior of newborn pups were not unambiguously affected by nitric oxide, and the same applies to changes of brain and body temperature or heart rate. In no case any correlation with changes of learning and/or memory could be established. Learning was dose dependently impaired relative to controls by intraperitoneal application of nitroarginine. L-arginine only slightly decreased numbers of trials to both criteria and partially abolished the blocking effect of nitroarginine on nitric oxide synthase. With the use of intracerebroventricular injections the positive impact of L-arginine on learning became highly significant. In 24-h memory, intraperitoneal injections of L-arginine enhanced the retention indexes. The impairing effect of nitro-L-arginine significantly increased with delaying after-learning application intervals, being more pronounced at the 3-h than at 0-h interval. Here also, its effect was partially abolished by L-arginine. Effects of nitric-oxide availability in brain after intracerebroventricular application of these substances at 16 various post-learning intervals were assessed on memory processing and retrieval. A general enhancing effect of increased nitric-oxide supply on 24-h retention indexes was found through all studied intervals, which was not, however, monotonous, but several peaks appeared with application at 3, 6, 18 and 23.5 h after learning. On the other hand, the suppressive effect of NArg was not evident relative to saline before the 6-h post-learning injection delay. These results show that nitric oxide exerts a considerable central modulatory effect on learning, memory processing and retrieval at the very early postnatal period of the rat. The efficiency of nitric-oxide manipulations depends on its actual bioavailability in the brain and the stage of memory processing.

The influence of 3-aminopropansulphonic acid (3-APS) on thalamic neurons.

The possible pathways conducting pain are still being discussed. One of the possible pathways may pass through the centrum medianum (CM). In the present study the activity of neurones of CM in cats was recorded using glass-micropipettes. 3-aminopropansulphonic acid (3-APS), which is a GABA analogue was administered intravenously in a dose of 0.1, 0.2, 0.5 and 1.0 mmol/kg. The depressive effect starts at the dose of 0.2 mmol/kg. The duration of the effect depends on the dose of 3-APS. Hence 3-APS has a very strong effect on other thalamic neurones so that it may be used for influencing their activity.