Traumatic Brain Injury Models in Zebrafish (Danio rerio)

Neuroscience and Behavioral Physiology - Current medicine has a high level of interest in studies of the pathogenesis of traumatic brain injury (TBI). This comes particularly from high levels of...     

Prolonged Social Isolation and Social Instability in Adolescence in Rats: Immediate and Long-Term Physiological and Behavioral Effects

After weaning on the 21st day of life, Wistar rat pups were kept in groups of 4–5 individuals for six weeks (control group), in individual cages (social isolation group), or were subjected to alternate days of isolation and housing in groups of 10 rats with constant rotation of partners (social instability group). Some of the animals were then decapitated for investigations, while the remainder were tested and left undisturbed for two months in groups of 4–5 individuals. The animals were retested as adults. Body, thymus, and adrenal weight were measured, along with blood corticosterone levels at rest and in acute stress; basal testosterone levels, basal and stress systolic arterial blood pressure, and the amplitude and prepulse inhibition of the acoustic startle reaction were assessed, and the behavioral manifestations of anxiety and depression were evaluated. The results showed that social environment factors in adolescence affected the animals’ physiological and behavioral characteristics, some effects being transient and settling on subsequent housing in stable groups, others persisting into adulthood, and a third group becoming significant only as rats became adults.     

Involvement of the catecholamine mechanisms in the activation of mouse hypophyseotesticular complex induced by the female presence effect

We have studied the role of the adrenergic and dopaminergic mechanisms in the activation of the endocrine testicular function of CBA/Lac and A/He male mice induced by the presence of a female in estrus without any tactile contact with a male. The-adrenoreceptor blocker phentolamine inhibited an increase in the peripheral blood plasma testosterone level caused by the receptive female challenge. Propranolol blockade of -adrenoreceptors abruptly increased the stimulating effect of the receptive female presence on the blood testosterone level. The expression of the adrenoblocker action on the blood male sex hormone level depended on a male genotype. The dopamine receptor blocker pimozide produced a moderate effect on the blood testosterone but an attempt to separate its influence into the male sex hormone tonic secretion and the blood testosterone level against a background of sexual activation failed. It was concluded that the adrenergic mechanisms were involved in the activation of the hypothalamo-hypophyseotesticular complex induced by the presence of the receptive female.Translated from Problemy Éndokrinologii, Vol. 32, No. 6, pp. 55–59, November–December, 1986.     

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

A dose-dependent the effect of 5HT_2C-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. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 142, No. 11, pp. 541–544, November, 2006     

Effect of serotonin 5-HT1A receptor agonists on sexual motivation of male mice

The effect of selective agonists of serotonin 5-HT_1A receptors on sexual arousal (its behavioral and hormonal components) in male CBA mice caused by estral females was studied. Injections of 8-OH-DPAT, flesinoxane, and ipsapirone significantly decreased the main behavioral parameter of sexual motivation (duration of the male's stay near the wall separating it from the receptive female). The activating effect of the female on the pituitary gonadal system of the male was completely blocked: the blood testosterone level did not increase. Therefore, the behavioral and hormonal components of sexual activation of males are regulated by the serotonin mechanisms alone, in which the cerebral 5-HT_1A receptors are involved. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 127, No. 2, pp. 224–226, February, 1999     

Chronic Administration of Imipramine Normalizes Decreased Sexual Motivation and Increased Predisposition to Catalepsy Induced by Propylthiouracil in Rats

Thyroxine synthesis inhibitors increase the predisposition to catalepsy and decrease sexual motivation and the amplitude of the acoustic startle reflex in rats. The sensitivity of these behavioral changes to antidepressants remains uncertain. Chronic administration of the classical tricyclic antidepressant imipramine (15 mg/kg, 21 days) prevented the appearance of high sensitivity to catalepsy and the decrease in sexual motivation in Wistar rats given propylthiouracil (50 mg/liter, 28 days), without altering the amplitude of the startle reflex. Normalization of behavior in response to imipramine was not associated with changes in movement activity in the open field test or the animals’ body weight. There was also no change in the expression of the 5-HT_2A serotonin receptor gene in the frontal cortex. The model of propylthiouracilinduced catalepsy with reduced sexual motivation in rats has potential for studying the role of thyroid abnormalities in the development of depression and the mechanisms of action of antidepressants. Translated from Zhurnal Vysshei Nervnoi Deyatel’nosti imeni I. P. Pavlova, Vol. 58, No. 2, pp. 217–225, March–April, 2008.     

Effects of Sexual Experience on Sexual Motivation in Copulatory Behavior in Male Rats

The effects of sexual experience on the behavior of one-year-old male Wistar rats in conditions excluding direct interaction and in conditions of direct contact with potential sexual and social partners were studied. Interest in a social partner on the other side of a partition was most strongly demonstrated by sexually experienced males, while sexually naive males showed the greatest interest in conditions of direct contact. All males showed maximum activity levels in the presence of a receptive female. Sexual experience in males had no effect on the motivational component of male sexual behavior, i.e. sexual excitation: the levels of sexual motivation in the presence of a receptive female were identical in sexually naive and experienced male rats. However, sexual experience produced fundamental changes in the nature of the consumatory stage of male sexual behavior on interaction with a receptive female, significantly increasing its expression. There were increases in measures of copulatory behavior such as the numbers of mountings and intromissions while the latent periods of their appearance decreased. There was also an increase in the proportion of males demonstrating elements of copulatory behavior in relation to partners of predominantly social significance.     

Effect of Monoamine Oxidase Gene Knockout on Dopamine Metabolism in Mouse Brain Structures

Experiments were performed on knockout Tg8 mice lacking monoamine oxidase A gene that plays a major role in dopamine catabolism. The study by the method of high-performance liquid chromatography revealed considerable regional differences in the contents of dopamine and its metabolite dihydroxyphenylacetic acid in brain structures of these animals. Tg8 mice differed from the parent C3H/HeJ strain by low level of dihydroxyphenylacetic acid in the striatum, midbrain, hypothalamus, and hippocampus and high concentration of dopamine in the striatum. No differences were revealed in the contents of dopamine and dihydroxyphenylacetic acid in the frontal cortex and amygdala. The 2.4-4.8-fold decrease in the content of dihydroxyphenylacetic acid in various brain structures was not accompanied by changes in dopamine concentration. These data reflect the effective compensation for deficiency of dopamine metabolism. Our results suggest that monoamine oxidases A and B and catechol-O-methyltransferase play different roles in dopamine metabolism in various brain structures.     

Hypothalamic tryptophan hydroxylase and the hypothalamic-pituitary-adrenocortical response to water deprivation and hydration in vasopressin-deficient and normal rats

The effects of water deprivation and hydration on plasma corticosterone concentration and the activity of tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin (5-HT) biosynthesis, in the hypothalamus of vasopressin- (AVP-) deficient homozygous Brattleboro and normal Wistar rats were studied. In the Wistar rats, water deprivation caused an increase in the TPH activity in the anterior and middle (infundibular) parts of the hypothalamus, while hydration did not affect the activity of the enzyme in the anterior hypothalamus but produced an increase in its middle part. In contrast, in the Brattleboro rats, water deprivation had no effect on TPH activity in the anterior and middle parts of the hypothalamus but hydration produced a decrease in TPH activity in the anterior hypothalamus. After 48 h of water deprivation, the plasma corticosterone concentration significantly increased in water-deprived and decreased in hydrated Wistar rats. Under water deprivation, the rise in corticosterone concentration in the homozygous Brattleboro rats was significantly greater than that in the Wistar rats. The data provide evidence that the CRH-like activity of AVP is not necessary for activation of the hypothalamic-pituitary-adrenal system induced by water deprivation. The observations show that AVP is involved in the activation of TPH induced by water deprivation. This suggests that AVP modulates the metabolism of 5-HT and the response of the 5-HT-ergic system to water deprivation.     

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. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 92, No. 6, pp. 751–760, June, 2006.