[Immobility and hyperthermia in tail suspension test: the association with Porsolt test and startle response in 11 inbred mouse strains, and the effect of MAO A knockout].

The tail suspension test (TST)-induced immobility and hyperthermia and acoustic startle response were studied in 11 mouse inbred strains and in MAO A knockout Tg8 mice. Significant genotypic differences in TST-induced immobility rather than hyperthermia and the lack of correlation between the expression of immobility and hyperthermia were found. Positive genotypic correlation between immobility in the TST and Porsolt test as well as TST-induced immobility and acoustic startle response was shown. Genetic knockout of the main enzyme in serotonin and catecholamines metabolism, MAO A, decreased the startle response and TST-induced hyperthermia but had no effect on TST-induced immobility in Tg8 mice indicating the differences in neurochemical regulation of these TST-induced responses. The results support the validity of the TST as dry-land version of the forced swimming test and draw attention to TST-induced hyperthermia as an animal model of response to uncontrollable, inescapable stress demonstrated in humans.

Effects of administration of sodium glutamate during the neonatal period on behavior and blood corticosterone levels in male mice.

Treatment of male DBA/2 mice with sodium glutamate (4 mg/g) on postnatal days 1, 3, 5, 7, and 9 induced reductions in the numbers of square crossings, vertical rearings, excursions to the center, and the time spent in the center in adulthood, as compared with a group of males given physiological saline at the same times. These measures showed no change as compared with intact animals. In the light-dark test, the time spent by mice in the light sector was greater after administration of sodium glutamate than after administration of physiological saline but did not differ from that in intact animals. In the acoustic startle reflex test, sodium glutamate decreased startle amplitude but had no effect on the magnitude of prestimulus inhibition. Sexual motivation in males decreased after sodium glutamate, physiological saline producing a tendency to decreased sexual motivation. Neonatal administration of sodium glutamate increased basal blood corticosterone in adult males by a factor of 4, while physiological saline had no effect on this measure. These results lead to the conclusion that neonatal administration of sodium glutamate decreases motor and investigative activity, anxiety, and sexual motivation in adult male mice and increases basal corticosterone. Physiological saline increased all these parameters apart from sexual motivation, though this was not associated with changes in basal corticosterone.

Immobility and hyperthermia in the tail suspension test: association with the Porsolt test and the reflex startle reaction in 11 inbred mouse strains and the effects of genetic knockout of MAO A.

Immobility and hyperthermia induced by unavoidable stress imposed by the tail suspension test (TST) and the acoustic startle reaction were assessed in mice of 11 inbred strains and in Tg8 mice, which have genetic knockout of MAO A. Sharp genotypic differences in immobility were seen, while there was no correlation with the hyperthermic response to the TST. A correlation was found between the extent of immobility in the TST and the startle reaction. Studies of 11 strains of mice revealed a positive correlation between the duration of immobility in the TST and the Porsolt "despair test." Genetic knockout of MAO A, one of the key enzymes in catecholamine and serotonin metabolism in the brain, weakened the startle reaction and TST-induced hyperthermia but had no significant effect on the immobility of Tg8 mice, which provides evidence of differences in the neurochemical regulation of these reactions. These data provide grounds for using the TST as a "dry" Porsolt test and identify TST-induced hyperthermia as a model for reactions to unavoidable stress.

Hypothermic effect of 5-HT1A receptor agonist: comparison of intranasal, intraperitoneal, and subcutaneous routes of administration.

The hypothermic effects of 5-HT1A serotonin receptor agonist 8-OH-DPAT after intranasal, intraperitoneal, and subcutaneous administration were compared. In a dose of 1 mg/kg 8-OH-DPAT induced similar thermal reactions after administration by all three routes. In a dose of 0.5 mg/kg 8-OH-DPAT caused no appreciable changes in body temperature after intraperitoneal injection and decreased it after subcutaneous and intranasal administration. No genotypic differences in the effects of 5-HT1A receptor agonist administered by different routes were detected in four inbred mouse strains.

Effect of 5HT2C-receptor agonist MK-212 on blood corticosterone level and behavior in mice.

A dose-dependent the effect of 5HT2C-receptor agonist MK-212 on mouse behavior was demonstrated. Intraperitoneal injection of MK-212 in high doses (0.5 and 1.0 mg/kg) increased blood level of corticosterone in mice and reduced their motor activity. In low doses of 0.1 and 0.2 mg/kg, the agonist reduced anxiety, but had no effect on motor activity. It is hypothesized that low doses of MK-212 exhibited anxiolytic activity in mice.

[The effect of neonatal administration of monosodium glutamate on behavior and blood corticosterone level].

DBA/2 male mice were treated with monosodium glutamate (MSG) in a dose of 4 mg/g on 1, 3, 5, 7, 9 days after birth. Saline treated and intact males were used as control groups. MSG treated males displayed decreased number of crossed squares, rearings, entries in the centre and time in the centre of open field in comparison with saline-treated but not intact animals. Time in the light compartment of the light-dark box was increased in MSG-treated mice versus both saline treated and intact animals. MSG administration reduced acoustic startle response but did not affect the magnitude of prepulse inhibition of the startle reflex. Sexual motivation in male mice was reduced by MSG, the same trend was observed after saline treatment. MSG administration increased corticosterone basal level 4-fold while saline treatment did not affect it. These data suggest that neonatal administration of MSG decreases locomotion, exploratory activity, anxiety in male mice, while corticosterone level is increased. Saline treatment increases these parameters (except sexual motivation), and this augmentation is not connected to changes in corticosterone basal level.