Oestrual Phase at first exposure to Predator-induced Stress Determines Pattern of Alterations in Oestrous Cycle and Endocrine Response in the Rat.

Stress has been acknowledged as one of the aetiologies of female reproductive dysfunction, yet the mechanismsinvolved are not totally elucidated. Based on the paucity of information on how predator-induced stress (PS) affects oestrouscycle in rats, this study was designed to investigate the effect of PS on the oestrous cycle in rats. Forty-eight (48) SpragueDawley rats were used for this study. They were randomly divided into Control and PS group. Each group was divided intofour subgroups (n=6/group) according to the phases of oestrous cycle. Stress was induced by exposing rats to cat (predator)for 60 minutes/day for 14 consecutive days. PS caused significant disruption of the oestrous cycle. In animals subjected toPS at proestrus (PS-proestrus) and oestrus (PS-oestrus), percentage occurrence of proestrus, oestrus and metestrus phaseswere significantly reduced compared with control. In animals subjected to PS at metestrus (PS-metestrus) and diestrus (PSdiestrus), percentage occurrence of oestrus phase was not significantly affected. In all animals exposed to PS, percentageoccurrence of diestrus was significantly increased regardless of the phase of first exposure compared with control.Corticosterone and prolactin levels were significantly elevated in PS groups compared with control. Progesterone wassignificantly increased in animals at diestrus phase compared with oestrus phase and respective phases in control. Oestradiolwas significantly reduced in PS group compared with control at oestrus phase but not significantly different at diestrus phase.Luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels were significantly lower in PS groups at oestrusphase compared with diestrus phase. This study shows that PS disrupts the oestrous cycle secondary to perturbation ofhormonal control of female reproduction and is influenced by the phase at first exposure to stress.

Analgesic activity of aqueous leaf extract of Phyllanthus amarus.

Various doses of the aqueous extract of Phyllanthus amarus (AEPA) were investigated for analgesic and anti-inflammatory activities using both thermal and chemical models of pain assessment in rats. The extract caused a significant (P < 0.05) dose related increase inhibition of the carrageenan-induced paw oedema in the rats. The inhibition produced by 200 mg/kg AEPA (70.20%) was significantly higher than that of the reference drug (Acetylsalicylic acid). The extract produced a marked analgesic activity by inhibiting both early and late phases of pain stimulus in Formalin-induced paw licking rats and also a significant and dose related increase in inhibiting the mean tail immersion duration (MITD) at varying water bath temperature (50 degrees C, 55 degrees C and 60 degrees C). This study thus established the anti-inflammatory and analgesic activities of Phyllanthus amarus.

Antifertility effect of calcium channel blockers on male rats: association with oxidative stress.

PURPOSE: Calcium ions are vital in many biologic processes including a variety of enzymatic reactions, activation of excitable cells, coupling of electrical activation to cellular secretion, haemostasis, bone metabolism and sperm functions. Calcium channel blockers (CCB) appear to have a reversible anti-fertility effect on male rats which does not occur through inhibition of the pituitary-gonadal axis. While the effects of CCB on male reproductive function have been investigated, less information is available regarding other reproductive indices and the underlying mechanism in the pathogenesis of male reproductive dysfunction. Therefore, the involvement of oxidative mechanisms in the adverse manifestation induced by CCB on male reproductive functions is investigated in this study. METHODS: For this purpose, lipid peroxidation; enzymatic antioxidants such as superoxide dismutase, catalase and glutathione reduced; epididymal sperm count, motility; histopathology of the testes, epididymis, seminal vesicle, prostate glands; and reproductive performance were determined. RESULTS: CCB administration in rats causes significant oxidative stress in the male reproductive milieu in term of increase in malondialdehyde (MDA) level and a concomitant decrease in catalase, superoxide dismutase and reduced glutathione enzyme activities in the testes. In addition, CCB treatment significantly decreased the sperm count, sperm motility, fertility index, implantation count, and litter size in this study. CONCLUSION: There is substantial evidence that CCB induces significant oxidative stress in the testes, which appears to be responsible for the adverse effects of decreased sperm count and motility ultimately leading to reduced fertility in rats.

Anti-diabetic and anti-oxidant effects of Zingiber officinale on alloxan-induced and insulin-resistant diabetic male rats.

This study was designed to investigate the hypoglycaemic and anti-oxidant effects of Zingiber officinale on experimentally induced diabetes mellitus using alloxan and insulin resistance. Aqueous extracts of raw ginger was administered orally at a chosen dose of 500mg/ml for a period of 4 weeks to alloxan-induced diabetic and insulin resistant diabetic rats. The experimental rats exhibited hyperglycaemia accompanied with weight loss to confirm their diabetic state. Ginger effectively reduced fasting blood glucose and malonydealdehyde levels in alloxan-induced diabetic and insulin resistant diabetic rats compared to control and ginger only treated rats. Furthermore, ginger increased serum insulin level and also enhanced insulin sensitivity in alloxan-induced diabetic and insulin resistant diabetic rats compared to control and ginger only treated rats. The results of the study clearly show that dietary ginger has hypoglycaemic effect, enhances insulin synthesis in male rats and has high antioxidant activity. One of the likely mechanisms is the action of malonydealdehyde, which acts as a scavenger of oxygen radicals.

Garlic and vitamin E provides antioxidant defence in tissues of female rats treated with nicotine.

Nicotine is known to induce oxidative stress in rat tissues and the antioxidant properties of garlic have been reported. This study was designed to determine if the peroxidative damage caused by nicotine administration can be effectively prevented with garlic juice, and vitamin E, a known antioxidant.Four groups of six rats each were divided into: Group I: (control) received 0.2ml of 0.9% normal saline, group II (received nicotine 0.6mg/kg b.w subcutaneously), group III (received nicotine 0.6mg/kg b.w + garlic juice 100mg/kg b.w orally), and group IV (received nicotine 0.6mg/kg b.w + Vitamin E 100mg/kg b.w orally). All animals were treated for 21 days. The pituitary gland, ovary, uterus, heart, liver and kidney of the animals were harvested, weighed and homogenized. Malondialdehyde (MDA), superoxide dismutase (SOD) and reduced glutathione (GSH) were then measured.Concentration of MDA was significantly increased in tissues of nicotine treated rats when compared with the control. In group III and IV, MDA levels were significantly reduced when compared with nicotine group. The activities of SOD and GSH significantly decreased in group II (nicotine only) rat tissues, while it was significantly increased in group III and IV rat tissues. The study showed that garlic juice extract (100mg/kg b.w) and vitamin E (100mg/kg b.w) administration prevented oxidative damage in rat tissues treated with nicotine. The study also showed that vitamin E has a more potent antioxidant activity than garlic juice in preventing nicotine induced oxidative damage in rat.

Effect of nicotine administration on weight and histology of some vital visceral organs in female albino rats.

It has been emphasized that cigarette smoking is not always synonymous with nicotine administration but the toxic effect of cigarette has often been associated with the nicotine content in cigarette. Epidemiologic studies have clearly indicated that cigarette smoking have many deleterious effects on visceral tissues in women. However it is not certain whether this effect is produced entirely by nicotine as cigarettes contain other toxic substances. Using an animal model, the direct effect of nicotine administration on viscera tissues in female albino rats was investigated. Twenty-four female rats with regular oestrous cycle in the same phase of the cycle were divided into two equal groups with each group receiving 0.5 mg/kg nicotine and 0.9% normal saline S.C. daily respectively. Six rats from each group were killed by cervical dissociation after 30 and 60 days treatment. The ovary, uterus, brain, kidney, heart, adrenal, pituitary and the liver were removed, weighed and histological study carried out. Weights of the ovary, kidney, pituitary and uterus were significantly [P<0.05] reduced following nicotine treatment while weights of the heart and liver increased with 60 days treatment with the appearance of cartilaginous cells in the heart and deposition of adipose around the portal vein in the liver. Necrosis, congestion, fibrosis, follicular and endometrial degeneration were observed in the brain, pituitary, kidney, ovary and uterus respectively. No significant difference was noted between the weekly growth rates in nicotine treated [5.13+/-0.29] and control [5.25+/-0.18] animals. Nicotine has deleterious effects on some vital visceral organs with observations similar to those reported in women smokers.

Effect of nifedipine on reproductive functions in male rats.

BACKGROUND: After life itself, fertility is probably the most highly prized human possession. Yet, while medical treatment of the individual naturally demands priority, relatively little attention is paid to the effects of treatment on reproductive function. OBJECTIVE: To investigate the effect of the calcium channel blocker, nifedipine, on sperm functions and identify the possible mechanism of action. METHODS: Twenty four (24) male rats weighing 150-170 g were divided into three groups of eight rats each. Group 1 (control) received distilled water; Group 2, received nifedipine 0.57 mg/kg; and Group 3, received 0.57 mg/kg and serve as a recovery group. Treatment was done orally and it lasted for 30 days. Animals in Group 3 were allowed another 30 days after drug withdrawal for recovery. Sperm count, motility, morphology and serum testosterone level were evaluated. The testes were removed, weighed and prepared for histological studies. RESULTS: The weight of the testis and epididymis were significantly reduced (P < 0.05) with administration of nifedipine. There were significant decreases (P < 0.05) in epididymal sperm count and motility. Serum testosterone levels remained unchanged in treated rats. The histological section of the testis showed no biologically meaningful change compared with control tissue. CONCLUSION: Nifedipine appears to have a reversible deleterious effect on sperm functions in rats which is not mediated by ta change in testosterone secretion.