Stress-associated cardiovascular reaction masks heart rate dependence on physical load in mice.

When tested on the treadmill mice do not display a graded increase of heart rate (HR), but rather a sharp shift of cardiovascular indices to high levels at the onset of locomotion. We hypothesized that under test conditions cardiovascular reaction to physical load in mice is masked with stress-associated HR increase. To test this hypothesis we monitored mean arterial pressure (MAP) and heart rate in C57BL/6 mice after exposure to stressful stimuli, during spontaneous locomotion in the open-field test, treadmill running or running in a wheel installed in the home cage. Mice were treated with ß1-adrenoblocker atenolol (2mg/kg ip, A), cholinolytic ipratropium bromide (2mg/kg ip, I), combination of blockers (A+I), anxiolytic diazepam (5mg/kg ip, D) or saline (control trials, SAL). MAP and HR in mice increased sharply after handling, despite 3weeks of habituation to the procedure. Under stressful conditions of open field test cardiovascular parameters in mice were elevated and did not depend on movement speed. HR values did not differ in I and SAL groups and were reduced with A or A+I. HR was lower at rest in D pretreated mice. In the treadmill test HR increase over speeds of 6, 12 and 18m/min was roughly 1/7-1/10 of HR increase observed after placing the mice on the treadmill. HR could not be increased with cholinolytic (I), but was reduced after sympatholytic (A) or A+I treatment. Anxiolytic (D) reduced heart rate at lower speeds of movement and its overall effect was to unmask the dependency of HR on running speed. During voluntary running in non-stressful conditions of the home cage HR in mice linearly increased with increasing running speeds. We conclude that in test situations cardiovascular reactions in mice are governed predominantly by stress-associated sympathetic activation, rendering efforts to evaluate HR and MAP reactions to workload unreliable.

[c-fos Gene expression in the brain of rats with various exploratory and defensive behavior]. / Osobennosti ékspressii gena fos v mozge krys s razlichnym issledovatel'skim i oboronitel'nym povedeniem.

Groups of active and passive Wistar rats were revealed in the "open field" and "hole exploration" tests. The pronounced c-fos gene expression was found in different brain structures of rats preliminary subjected to electrodermal stimulation in the "step down" test. Marked differences in c-fos gene expression were observed in brain structures of rats with the active and passive behavior in the "open field", "hole exploration", and "step down" tests. The most pronounced and intensive c-fos gene expression was noticed in the passive rats.

[Neuroactive complexed zinc compounds from bovine brain]. / Neiroaktivnye kompleksnye soedineniia tsinka iz mozga krupnogo rogatogo skota.

The fraction obtained from acidic extract of bovine brain homogenate after several steps of chromatographic purification provokes spontaneous aggressive encounters in rats upon intracerebroventricular injection. The simultaneous long-term raising of electric shock-induced aggression with the suppressing of muricidal and intraspecies aggressive behaviour has been observed. Intravenous and intraperitoneal injections of this fraction induce no behavioural changes in rats. It has been determined that the fraction consists of complex compounds of zinc with various aliphatic amines. A similar or higher behavioural activity has been discovered in series of synthetic complexes of zinc with different ligands, that are suggested for use in modelling any nervous and psychiatric disorders connected with an increased aggression level.

[Is pain-induced aggression actually a defensive form of that behavior?]. / Deistvitel'no li agressiia, vyzvannaia bol'iu, iavliaetsia oboronitel'noi formoi dannogo povedeniia?

25-minute testing of aggressive reactions in constant pairs of male rats, elicited by electric shocks shows that electro-pain aggression of rats is not a homogeneous process, but consists of three successive stages: orienting-investigatory activity and attempts to get out of the chamber; defensive aggression; establishing of relations of domination-subordination and attacking aggression. Division in attacking rats and defending themselves, occurs mainly at final stages of testing (15-25 min); in some pairs reactions of attacking aggression are accomplished by the same rats. It is supposed that rats pain aggression is not a purely defensive form of this behaviour, but a modification of intermale aggression caused by specificity of laboratory conditions.

[Predatory aggressiveness of the rat after intraventricular administration of individual brain-specific proteins of the S-100 group and their peptide fragments]. / Khishchnicheskaia agressivnost' krys posle vnutrizheludochkovogo vvedeniia otdel'nykh mozgospetsificheskikh belkov gruppy S-100 i ikh peptidnykh fragmentov.

Intraventricular injections to rats of the basic fraction of the brain specific protein S-100 in a concentration of 3 mg/ml, significantly facilitates the formation of their predatory aggression induced by the alimentary deprivation and social isolation, expressed in mice killing. This effect is not produced by fragments of S-100 molecules obtained as a result of treatment of the basic protein fraction by proteolytic enzymes. Administration of the minor S-100 fraction, albumin and rats summate brain proteins did not influence animals predatory aggression.

[Inherent behavioral activity of rats administered different fractions of brain-specific S-100 proteins]. / Vrozhdennaia povedencheskaia aktivnost' krys pri vvedenii razlichnykh fraktsii mozgospetsificheskikh belkov gruppy S-100.

The intraventricular injection of brain specific S-100 proteins leads to the prolonged heterochronous changes of the inherent rat behaviour forms during the period of water and food needs restitution. The effects of various doses of S-100 proteins fractions on the behavioural activity differs in the degree of expression and in time of their onset. The specific influence of some S-100 proteins fractions on duration of the different inherent forms of rat behaviour can be explained by plurality of molecular mechanisms of their effects.