Süleyman Aydin

Effects of Hypericum perforatum L. and Hypericum calycinum L. extracts on the central nervous system in mice.

Hypericum species have been used as herbal remedies for the therapy of various diseases since ancient times. It has been reported that Hypericum perforatum is a useful herbal remedy for the treatment of neurological disorders such as coxalgia, menopausal neurosis, headache, hydrophobia, hypersensitivity, mental aliments, neuralgia, paralysis, spastic paralysis, spinal convulsion, spinal irritation, stiff neck, tetanus, etc. On the basis of recent clinical studies, the extracts prepared from H. perforatum have been found to be effective for the treatment of mild and moderate depressions with no special side effects. In the present study, the effects of H. perforatum and H. calycinum on the central nervous system were investigated using various behavioural models including swimming time, locomotor activity, tail-flick and hole-board experiments. According to the results obtained, it was found that the extracts prepared from Hypericum perforatum and Hypericum calycinum are as effective as antidepressant drugs, desipramine and trimipramine, which were used for the comparison of their effects with these two plant extracts in animal models. The findings obtained also suggested that the antidepressant effect of Hypericum calycinum may be as potent as that of Hypericum perforatum and may be used for therapeutic purposes in depression.

Analgesic activity of Nepeta italica l.

A screening study was performed on/by essential oils of Nepeta viscida Boiss and Nepeta italica L. using tail‐flick and tail immersion (52.5°C) methods. N. italica samples were collected from three differentlocalities of Turkey. Surprisingly, only one of the essential oils showed significant activity, which was blocked by naloxone, indicating the involvement of opioid receptors. This was seen only with the mechanical but not the thermal algesic stimulus, suggesting a specific activity on opioid receptors, excluding mu receptors. The same, active essential oil also exhibited a non‐competitive inhibition of acetylcholine contractions of isolated rat ileum but it was inactive on the isolated rat aorta. Furthermore, a correlation between the analgesic activity and the amount of 1,8‐cineole was noticed. Copyright

Nepetalactone : A new opioid analgesic from Nepeta caesarea Boiss.

The essential oils of Nepeta species including Nepeta phyllochlamys P. H. Davis, N. nuda L. ssp. nuda, and N. caesarea Boiss. have been screened by use of the tail‐flick and tail immersion (52.5°C) methods.

Investigation of Origanum onites, Sideritis congesta and Satureja cuneifolia essential oils for analgesic activity

Essential oils, obtained by Clevenger distillation, of Sideritis congesta P. H. Davis et Hub.Mor., Satureja cuneifolia Ten. and Origanum onites L. collected from two different localities were investigated for their analgesic activity by using the tail‐flick method in mice and by comparing with standard analgesic drugs, morphine and fenoprofen. Among the essential oils tested, marked analgesic activity was found to be specific only for Origanum onites. Surprisingly, the analgesic activity of Origanum oils seems to be dependent on the locality. Findings obtained in the present study strongly suggested that the analgesic activity is related to the carvacrol content of essential oils.

Endothelium-dependent and independent effects of garlic on rat aorta.

Effects of garlic on isolated rat aorta were investigated by comparing with those of acetylcholine and L-arginine in the presence and absence of endothelium. For this purpose, certain linear and non-linear regression models were applied for concentration-response curves obtained by acetylcholine, L-arginine and garlic in the rat aorta. Garlic caused dose-dependent relaxations in isolated rat aorta which were attenuated by the removal of endothelium as in the case of acetylcholine. However, the relaxant responses to acetylcholine, L-arginine and garlic were not completely abolished by the endothelial denudation. Application of a number of regression models for the vasorelaxant effects of acetylcholine and garlic revealed that mechanism(s) of the effect of garlic may be different from that of acetylcholine. Furthermore, it was noted that L-arginine-induced relaxations, but not those induced by acetylcholine and garlic, are enhanced by a 2 or 4 h incubation period in the bathing medium. The findings obtained strongly suggested that the vasorelaxant effect of garlic is important in its hypotensive activity and mediated by the production of endothelium-and/or muscle-derived relaxing factors.

Effects of Hypericum calycinum L. Extract on the Central Nervous System in Mice

Hypericum species have been used as herbal remedies for the therapy of various neurological disorders. In the present study, the effects of Hypericum calycinum on the central nervous system were investigated using various behavioural models including swimming time, locomotor activity, tail‐flick and hole‐board experiments. According to the results obtained, it was found that the extract prepared from H. calycinum is as effective as the antidepressant drugs, desipramine and trimipramine, which were used for comparison with this plant extract in animal models.

Calmodulin content and in vitro contractility of duodenum from streptozotocin-induced diabetic rats: effects of insulin therapy and calmodulin antagonism.

The effects of experimental diabetes and insulin treatment on the decreased reactivity of isolated rat duodenum to KCl and calmidazolium, a specific calmodulin antagonist, were examined. After 8 weeks of streptozotocin diabetes, the contractile effect of KCl and the non-competitive antagonistic effect of calmidazolium against KCl on isolated rat duodenum were decreased. Calmodulin levels, as measured by radioimmunoassay, were also found to the decreased in duodenum from streptozotocin-diabetic rats. Neither impaired reactivity to KCl nor decreased calmodulin levels in diabetic rat duodenum were corrected by treatment with insulin (10 IU/kg for 20 days). Following insulin treatment, there was only a partial correction in the antagonistic effect of calmidazolium as shown by the increase in non-competitive antagonist affinity constant.

The involvement of endogenous opioid mechanisms in the antinociceptive effects induced by antidepressant drugs, desipramine and trimipramine

The present study was designed to investigate the involvement of endogenous opioid systems in the antinociception induced by the antidepressant drugs, desipramine and trimipramine. For this purpose, the antinociceptive effects of desipramine (7.5 and 15.0 mg/kg i.p.) and trimipramine (5.0 and 10.0 mg/kg i.p.) were compared to that induced by morphine (0.2 and 2.0 mg/kg i.p.) in the tail-clip model in mice. Naloxone (0.3 and 3.0 mg/kg i.p.), a non-specific opioid receptor antagonist, inhibited morphine-induced antinociception in mice, whereas the antinociceptive effects of antidepressant drugs were found to be resistant to naloxone blockade to some extent, since only the higher concentration of naloxone (3.0 mg/kg i.p.) caused significant inhibition of the effects of antidepressant drugs. In contrast, naltrindole (1.0 mg/kg i.p.), a specific delta-receptor antagonist, inhibited antinociception induced by desipramine and trimipramine in this test, while it inhibited the antinociceptive effect of morphine only partly. None of the opioid antagonists produced a significant effect in the tail-clip experiment when they were injected alone. Based on these findings, we concluded that endogenous opioids are involved in the antinociceptive effects of the antidepressant drugs using different mechanisms.

Effect of insulin treatment on smooth muscle calmodulin levels in rats with long-term streptozotocin-diabetes

Altered responses to several agonists have been reported in various smooth muscles from experimentally-diabetic animals suggesting a defective contractile process of smooth muscle. Recently, decreased smooth muscle calmodulin levels have been reported in streptozotocin-diabetic rats. However, the effectiveness of insulin on the decreased calmodulin levels in diabetic rats has not been questioned. Therefore, the present study was designed to examine the effect of insulin on smooth muscle calmodulin levels from streptozotocin-diabetic rats. Calmodulin levels of the smooth muscle were measured by a radioimmunoassay technique. Streptozotocin diabetes caused a significant decrease in tissue calmodulin levels of smooth muscles. Insulin therapy for 20 days did not correct the changes in calmodulin levels of rat smooth muscles, although it normalised blood glucose in streptozotocin-diabetic rats. These findings suggest that the altered smooth muscle calmodulin may contribute the defective contractile responses in diabetes and these changes may be resistant to insulin therapy.