Negatively charged air ions are of interest of researchers and physicians as an effective means of prophylaxis and treatment of a wide range of diseases. Our previous studies showed that negatively charged air ions have normalizing effects on important physiological functions in rats subjected to prolonged chronic stress [3] and acute immobilization stress [4]. These studies used either long-lasting (three weeks) exposure to air ions during chronic induction of neurosis or pre-treatment (daily for one week) exposure before acute experiments in the immobilization stress model. It remained unclear whether short periods of exposure to air ions had prophylactic effects during the actual development of immobilization stress. Since the adaptational abilities of the body, especially resistance to stress-inducing factors, can depend on the type of nervous system [1, 2, 6], studies were performed with consideration of the typological characteristics of the animals' behavior. The aim of the present work was to study these points.Experiments were carried out using 64 male Wistar rats (250-350 g). All animals were kept in standard animal-house conditions with natural illumination. Air was ionized using an t~lion-132 device (an up-todate modification of the "Chizhevskii lamp" electroeffluvial air ionizer) for 1 h as animals were immobilized. The intensity of air ion formation was 31.6 ions/sec. Rats were placed 2 m from the air ionizer.llnstitute of Higher Nervous Activity and Neurophysiology, Russian Academy of Sciences, Moscow.

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Studies of identical groups of male Wistar rats after preliminary selection to give groups including extreme behavioral types with low and high rankings on the anxiety scale showed that blood testosterone concentrations in intact rats (controls) correlated negatively with anxiety ranking, i.e., minimal hormone concentrations (no greater than 5 nM) corresponded to high levels of anxiety - with a predominance of passive defensive behavioral components on testing. Short-term exposure to a "death threat" situation (sight of a boa attacking and eating two individuals from the group of rats) impaired this correlational relationship in a manner comparable to the sequelae of chronic neuroticization by unavoidable pain stimulation. Impairments were manifest as scatter in measures in low-anxiety animals (3-21 nM). This characteristic, reflecting the multitude of adaptive pathways in the population in threat situations, distinguishes this type of action from neuroticization by unavoidable pain stimulation, which leveled out individual differences and decreased the hormone level.

The levels of monoamines and their metabolites were studied by HPLC with electrochemical detection in homogenates of hypothalamus, hippocampus, prefrontal cortex, and amygdala in intact and neuroticized Wistar rats with different types of behavior in the open field and forced swimming tests. Intact rats with intermediate levels of activity and depressivity had higher serotonin concentrations in the hypothalamus and lower noradrenaline and hydroxyindoleacetic acid levels in the hippocampus than rats characterized by low activity and high depressivity. In neuroticization, the levels of study monoamines and their metabolites decreased in all the brain structures investigated with the exceptions of an increase in the dopamine concentration in the hippocampus and the dihydroxyphenylacetic acid concentration in the prefrontal cortex. The effect of neuroticization on the neurotransmitter systems in all study structures except the hypothalamus depended on the typological characteristics of the rats. This was most marked in rats with the extreme types of behavior--active and passive--in which changes in monoamine and metabolite contents were seen in all brain structures studied. Rats of the intermediate type showed no changes in any of the substances studied in the hippocampus.