Amine neurotransmitter levels in male and female rats through developmental periods

The effect of a single dose of Mk-801 use on adult brain tissue after an experimental head trauma model applied in immature rats

OBJECTIVE

Within the scope of this research, the long-term effects of experimental blunt head trauma on immature rats and MK-801 administered acutely after trauma on the brain tissue will be examined. In addition, the impact of trauma and MK-801 on Nestin and CD133, which are essential stem cells, will be evaluated by immunohistochemical and ELISA methods.

METHODS

In this study, the contusion trauma model was used. Sprague Dawley rats 30 7-day-old were divided into three groups: Group 1 (n = 10) control group, Group 2 (n = 10) trauma Group (head trauma applied), and Group 3 (n = 10) MK-801 + trauma Group. In the third group, immediately after head trauma, MK-801 (Sigma M107) dissolved in physiological saline was administered as a single dose of 1 mg/kg ip.

RESULTS

The concentration of nestin was significantly higher in the control group compared to both the trauma and trauma+drug groups (p < 0.001). CD133 was statistically significantly higher in the control group compared to the other two groups (p = 0.002). It was determined that the differences in Nestin CA1 and DG measurements resulted from the trauma and control and trauma and trauma+drug groups, and the differences in CD133 CA1 and DG measurements resulted from the trauma and control group.

CONCLUSION

The positive effect of MK-801 on neuroprotective and neuronal proliferation was elaborated. Administration of MK-801 significantly induced nestin and CD133 concentrations in the injured tissue.

Effects of low-doses of methamphetamine on d-fenfluramine-induced head-twitch response (HTR) in mice during ageing and c-fos expression in the prefrontal cortex

BACKGROUND

The head-twitch response (HTR) in mice is considered a behavioral model for hallucinogens and serotonin 5-HT_2A receptor function, as well as Tourette syndrome in humans. It is mediated by 5-HT_2A receptor agonists such as ( ±)- 2,5-dimethoxy-4-iodoamphetamine (DOI) in the prefrontal cortex (PFC). The 5-HT_2A antagonist EMD 281014, can prevent both DOI-induced HTR during ageing and c-fos expression in different regions of PFC. Moreover, the nonselective monoamine releaser methamphetamine (MA) suppressed DOI-induced HTR through ageing via concomitant activation of inhibitory 5-HT_1A receptors, but enhanced DOI-evoked c-fos expression. d-Fenfluramine is a selective 5-HT releaser and induces HTR in mice, whereas MA does not. Currently, we investigated whether EMD 281014 or MA would alter: (1) d-fenfluramine-induced HTR frequency in 20-, 30- and 60-day old mice, (2) d-fenfluramine-evoked c-fos expression in PFC, and (3) whether blockade of inhibitory serotonergic 5-HT_1A- or adrenergic ɑ₂-receptors would prevent suppressive effect of MA on d-fenfluramine-induced HTR.

RESULTS

EMD 281014 (0.001-0.05 mg/kg) or MA (0.1-5 mg/kg) blocked d-fenfluramine-induced HTR dose-dependently during ageing. The 5-HT_1A antagonist WAY 100635 countered the inhibitory effect of MA on d-fenfluramine-induced HTR in 30-day old mice, whereas the adrenergic ɑ₂ antagonist RS 79948 reversed MA's inhibitory effect in both 20- and 30- day old mice. d-Fenfluramine significantly increased c-fos expressions in PFC regions. MA (1 mg/kg) pretreatment significantly increased d-fenfluramine-evoked c-fos expression in different regions of PFC. EMD 281014 (0.05 mg/kg) failed to prevent d-fenfluramine-induced c-fos expression, but significantly increased it in one PFC region (PrL at - 2.68 mm).

CONCLUSION

EMD 281014 suppressed d-fenfluramine-induced HTR but failed to prevent d-fenfluramine-evoked c-fos expression which suggest involvement of additional serotonergic receptors in the mediation of evoked c-fos. The suppressive effect of MA on d-fenfluramine-evoked HTR is due to well-recognized functional interactions between stimulatory 5-HT_2A- and the inhibitory 5-HT_1A- and ɑ₂-receptors. MA-evoked increases in c-fos expression in PFC regions are due to the activation of diverse monoaminergic receptors through increased synaptic concentrations of 5-HT, NE and/or DA, which may also account for the additive effect of MA on d-fenfluramine-evoked changes in c-fos expression. Our findings suggest potential drug receptor functional interaction during development when used in combination.

Stress in Neonatal Rats with Different Maternal Care Backgrounds: Monoaminergic and Hormonal Responses

The first 2 weeks of life in rats are known as the stress hyporesponsive period because stress responses in pups are diminished as compared to adult animals. However, it is considered a critical period in development in which infant rats are susceptible to environmental events, such as stressful stimuli and quality of maternal care received. These early life events have long-lasting effects, shaping a variety of outcomes, such as stress responsivity. This study investigated the effects of maternal care and sex differences on the response to an aversive stimulus in rat pups from high (HL) and low licking (LL) mothers. Plasma corticosterone, oxytocin, and central monoaminergic activity in 13-day-old rats submitted to cold stress were analyzed. Stress increased plasma corticosterone and marginally decreased hypothalamic dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratio. HL pups showed higher levels of plasma oxytocin than LL pups. The maternal effect was also detected in the hippocampus, in which 5-hydroxyindole-3-acetic acid/serotonin (5-HIAA/5-HT) ratio was increased in HL pups, independently of the sex and stress. Investigating the early life events is useful not only into understand the neurobiological and hormonal mechanisms underlying maternal and stressful influences on infant development into a healthy or psychopathological adult phenotype, but also to unveil the immediate outcomes on infancy.

Profound destructive effects of adolescent exposure to vincristine accompanied with some sex differences in motor and memory performance

Vincristine, an anticancer drug, is known to induce neuronal cell damage. We have elucidated the alteration in performance of the hippocampus and cerebellum following chronic vincristine treatment (0.2 mg·(kg body mass)–1·week–1) in male and female rats. Intraperitoneal injection of vincristine in adolescent rats caused impairment of motor and cognitive behavior. In the probe test, the length of path traveled and percent swimming time for vincristine-treated rats in the correct quadrant was significantly less than for the saline-treated (control) groups. The path length and time latency at the 2nd and 3rd blocks of trials for the male vincristine-treated group was significantly higher than that for the female saline- and the vincristine-treated rats. In the rod test, vincristine exposure impaired the motor coordination in both male and female rats. Exposure to vincristine caused a significant decrease in hanging time in male rats, compared with the saline- and the vincristine-treated female rats, while there were no differences between the female vincristine-treated rats and the saline-treated rats of both sexes. The rearing frequency, total distance moved, and velocity for both male and female rats were dramatically affected by exposure to vincristine. We have observed that the hippocampal and cerebellar functions of male and female rats were profoundly affected by exposure to vincristine, especially the male rats, suggesting a sexual dimorphism in the developing central nervous system that is affected by chemicals such as anticancer drugs.

Evaluation of age and sex differences in locomotion and catalepsy during repeated administration of haloperidol and clozapine in adolescent and adult rats

Adolescence is associated with characteristic behavioral patterns as well as with substantial neuronal pruning and re-organization of the brain. Recent research has determined that the effects of various centrally active drugs differ in adolescents and adults. This study examined the motor effects of two prototypic antipsychotics in adult [>postnatal day 70 (PN70)] and adolescent (PN30-PN39) rats. Rats were injected daily with saline, 0.3 mg/kg haloperidol, or 10 mg/kg clozapine for 10 days and activity and catalepsy were measured. Adolescents of both sexes were less sensitive to the cataleptic effects of haloperidol than were adults. Male adolescents were also less sensitive to the cataleptic effects of clozapine, although this difference was transitory. In contrast, female adults showed decreased sensitivity to clozapine's effects, differing from all other groups. These results suggest that adolescents of both sexes may be less sensitive to the extrapyramidal motor effects of haloperidol. Translational implications of the clozapine results are less clear; however, results suggest that developmental differences in neurochemical systems affected by clozapine that are also related to motor behavior may play a role. These results also emphasize the importance of age and sex as determinants of the pharmacological effects of these antipsychotics.