[Effects of extremely low frequency electromagnetic fields during foetal life on adulthood learning in male rat]

Background and aim: Our environment is exposed to electromagnetic fields by development and industrialization of life. The aim of this investigation was to evaluate the effects of extremely low frequency electromagnetic fields [5 and 25 Hz] during fetal life on adulthood learning in male rat

Methods: In this study forty eight Sprague Dawley pregnant rats [150+/-20g] were divided into six groups of eight: control, sham, and 5 or 25Hz and 50 or 500micro T. Duration of exposure was 4 hours per day [continuously from 8 to 12 A.M.] from first day to 15th day of gestation. We evaluated learning, body weight, brain weight, brain volume, brain weight to body weight ratio and brain density of 60 days-old male offsprings. The learning task was performed by shuttle box in the form of one-way active avoidance conditioning. The number of conditioning responses and latency periods was recorded. Data was statistically analyzed by Kruskal-wallis test

Results: Fetal life exposure to ELF EMF [25Hz/50micro T] improved learning, decreased body weight and increased brain weight to body weight ratio in male rat [P<0.05]. Fetal life exposure to 25 Hz/500 micro T, 5 Hz/500 micro T and 5 Hz/50 micro T increased body weight

Conclusion: Fetal life exposure to ELF EMF [25Hz/50micro T] could improve learning in male rats

effect of intra-CA1 agmatine microinjection on water maze learning and memory in rat

Reports on agmatine are controversial showing that it may improve memory, it can deteriorate memory and some did not notice any interference with learning and memory. In the present study, the effect of directly intra-CA1 agmatine microinjection on water maze learning and memory has been assessed. The cannuls were implanted in hippocampal CA1 regions of rats in a sterotaxic frame after general anesthesia. After one week recovery period, the animals were assessed in the reference memory version of water maze. Agmatine [1, 10, 100 or 200 microg/0.5 microl] or saline were infused 20 minutes before or immediately after training. Agmatine-treated rats did not show any significant difference neither in water maze acquisition nor in consolidation task in comparison with control and sham groups. Agmatine does not affect water maze learning and memory

Effect of c-peptide on cognitive dysfunction in type 1 diabetic rat

Diabetes mellitus is a common metabolic disorder that associates with structural and functional changes in central and peripheral nervous system and progressive decline in cognitive abilities. Recent experimental and clinical data suggested that C-peptide replacement during type 1 diabetes exerts beneficial effects on diabetic rats. Determine the effect of intraperitoneal [IP] injection of c-peptide on cognitive dysfunction in type 1 diabetic rats. 24 male Sprague dawly rats [230-300 gr] used for this project divided into 3 groups: 1. control group, 2. type 1 diabetic group and 3. Diabetic group that receive C-peptide [25 nmol/kg/daily for 28 day/IP]. Diabetes induced with IV injection of Streptozotocin [60mg/kg]. Twenty one days after onset of diabet, behavioral tests conducted for seven days. In reference memory assessment, the latency of finding platform during four days decline significantly in all groups [P<0.05]. Mean escape time in diabetic group was significantly longer in comparison to other groups [P<0.05] but in comparison to diabetic group with C-peptide group, memory impairement decline significantly [P< 0.05]. During three days of working memory test, the latency required for finding platform decreased significantly [P<0.05] but this time was longer in diabetic group [P<0.05]. C-peptide could improve memory in diabetic group. C-peptide had significant role in control and inhibition of memory disorder progression

[Effect of Testosterone on carrageenone induced inflammation in gonadectomized male rats]

Different nociceptive and inflammatory responses to noxious stimuli in male and female animals imply that sex hormones may affect on inflammatory factors, induction and intensity of the inflammation. The aim of the current study was to evaluate the effect of testosterone administration on carrageenone induced inflammation in gonadectomized male rats. Forty male Wistar rats were divided into four groups [n=8]. 1-The control rats without receiving any drug or surgical operation. 2-The sham - operated animals with surgical stress. 3-The gonadectomized rats, receiving 0.5 ml vehicle [olive oil] i.p. 4-The gonadectomized rats, receiving testosterone enantate [6 mg/100 gr body weight in 0.5 ml vehicle i.p.]. At the sixth day of gonadectomy operation, inflammation was induced by injection of 1% carrageenone in the right hind paw of rats. Edematous paw volume as an index of inflammation was determined by immersing it into the mercury container. Weight of paw in the mercury was measured and then the paw volume was calculated in relation to specific gravity of mercury [13.6gm/ml]. Data were statistically analyzed by SPSS software using ANOVA. The results showed that edematous paw volume significantly was reduced in testosterone enantate administrated gonadectomized rats compared to the control group [P<0.01]. It can be concluded that high dose of testosterone causes attenuation of inflammatory response. The testosterone anti-inflammatory effect is probably due to inhibition of inflammatory factors [Interleukins] production or decrease in receptors of inflammatory factors

[Different effects of testosterone on acute and chronic pain in gonadectomized male rats]

Nociception and behavioral responses to noxious stimuli are different in males and females. It seems that these differences are due to the effects of sex hormones on the pain mechanisms. The aim of the current study was to evaluate the effect of testosterone administration on nociception by formalin test in gonadectomized rats. In this study 32 male wistar rats were divided into four groups [n=8]; the control rats without receiving any drug or surgical operation, the sham - operated animals with surgical stress, the gonadectomized rats receiving 0.5 ml vehicle [olive oil] i.p., and the gonadectomized rats receiving testosterone enantate [6 mg/100 gr body weight in 0.5 ml vehicle i.p.]. On the sixth day after gonadectomy operation, formalin test was done in all rats. Pain scores in formalin test were statistically analyzed by SPSS and ANOVA. The results showed that testosterone caused an increase in pain score in acute phase of formalin test in gonadectomized rats compared with sham-operated group [p<0.001]. However, pain score in chronic phase was significantly reduced in testosterone received rats [p<0.001]. It can be concluded that testosterone increases nociception in acute phase of formalin test in gonadectomized rats. On the other hand, testosterone relieved pain during chronic phase. Anti-nociceptive effects of testosterone in chronic phase may be through central nervous system by interacting with endogenous pain modulatory systems

effect of thyroid activity on adult rat spermatogenesis

The influence of hypo- and hyper-thyroidism on spermatogenesis was studied in 60-day-old adult male Wistar rats. To confirm hypo- and hyper-thyroidism, the concentration of plasma thyroid hormones were assayed by radioimmunoassay. The hypothyroid state, induced by administration of 25 mg/kg/day methimazole for 5 successive days, resulted in significant decrease in the number of Sertoli cells, sperm count, Leydig cells and the diameter of seminiferous tubules. The hyperthyroid state, induced by administration of 1 mg/kg/day L-thyroxine for 10 successive days, increased the number of Sertoli cells, sperm count, Leydig cells and the diameter of seminiferous tubules. Serum levels of FSH and LH and testosterone were also evaluated. Hypo- and hyper-thyroidism had no effects on the concentrations of FSH and LH, while the concentration of testosterone was significantly increased in hyperthyroid state; it decreased in hypothyroid state in comparison with the control euthyroid rats. In conclusion, our data indicated that hypo- and hyper-thyroidism affect spermatogenesis through their effects on germinal, interstitial and Sertoli cells but not through the pituitary-gonadal axis

Effect of high- dosage of testosterone enanthate administration on the serum levels ofadrenocortical hormones in rat

Testosterone enanthate [TE] due to its anabolic effects is widely used by athletes to increase muscle strength. Despite widespread abuse of anabolic steroids, the endocrine effects of supraphysiologic doses of these compounds remain unclear. Our previous studies showed that the high doses of TE have some effects on the secretion of metabolic hormones. The aim of this study was to evaluate the effect [s] of high dosage of TE on serum levels of adrenocortical hormones in rat.In this study, 120 male Charles River rats [210-220g] were divided to five groups of 24. In group I, the control group, rats did not have any operation or injection. In group II rats were gonadectomized and received TE [5mg/100g B.W, i.p injection, weekly]. Group III was gonadectomized rats receiving vehicle [olive oil]. Group IV was sham-operated non-gonadectomized rats receiving the same dose of TE as group II. Group V was sham operated non-gonadectomiced rats receiving vehicle. In each group, blood samples were taken from eight rats after 21, 42, 63 days and the serum levels of testosterone, cortisol, aldostrone and corticotropin [ACTH] were measured by radioimmunoassy technique.The results showed that cortisol and aldostrone levels in TE receiving groups, were significantly lower and ACTH was higher than those of the other groups at day 21 [P<0.05]. In long term [63 days] these changes came back to the control levels.It seems that acute suppressive effects of high testosterone level on adrenocortical cells, decrease serum levels of cortisol and aldostrone and elavate ACTH. In long-term the feedback mechanisms modulate these effects via hypothalamic-hypophysial-adrenal axis

Effects of levothyroxine administration on ovulation rate and sex hormone levels in prepubertal and adult rats

Thyroid gland dysfunction is associated with disorders of female reproductive functions. The aim of this study was to examine the effects of hyperthyroidism on ovulation rate and peripheral sex steroid levels in prepubertal and adult rats. Two groups of female rats aging 30 days [prepubertal rats] and 60 days [adult rats] were made hyperthyroid by oral administration of levothyroxine daily. In the two control groups [n=10] rats with the same ages received the same volume of normal saline. After 10 days the serum levels of T[3], T[4], LH, FSH, estradiol and progesterone were measured by RIA technique and also sections of ovaries were prepared for histological studies. All ovarian follicles and corpora lutea were counted to estimate ovulation rate. The results indicated that serum estradiol and progesterone levels of adult hyperthyroid rats were significantly lower than those of the control group [p<0.05]. However, there was no significant difference between estradiol levels in the prepubertal hyperthyroid group and its control group. In the hyperthyroid groups the mean number of primary, secondary and antral follicles and corpora lutea was significantly less than those of control groups. It was concluded that high levels of plasma thyroid hormones resulted in lowered body weight and disturbed ovarian follicle development and differentiation leading to reduction in ovarian steroidogenesis and ovulation