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  Background & Objective: Herbal medicine has an old history with a broad application all over the world. Many researches have focused on the curative as well as antinociceptive effects of herbal extracts. In the previous study the analgesic effect of Chamomile extract containing 2 mg/kg essence in Rats which revealed a significant analgesic effect were studied. In this study it is planned to compare the analgesic effect of chamomile extract and Morphine (as a standard analgesic) in mice.

  Methods: This experimental study was carried out in Shahid Sadughi Medical School on 48 Syrian mice (25-30 grams) which were randomly divided into 8 groups. In this study the analgesic effect of intraperitoneal administration of Chamomile extract containing 2 mg/kg essence and different doses of Morphine (0.5, 1.0 and 2.0 mg/kg) were assessed by using Formalin Test (for chronic pain during 1 hr. post Formalin injection) and Tail Flick Test (for acute pain during 2 hr. post drug administration in 15 min. time intervals).

  Results: The results of this study showed that 2^nd phase of Formalin Test had more analgesic effect than that of 0.5 mg/kg morphine. In the case of Tail Flick Test its analgesic effect was prominent 30-90 min. after drug administration which was identical to the analgesic effect of 1.0 and 0.5 mg/kg Morphine Sulfate (P > 0.05).

  Conclusion: Data from this study confirms the analgesic effect of chamomile essence which was indicated in our previous study and that this analgesic effect is comparable with 1 mg/kg of morphine sulfate in both the Formalin TEST & Tail Flick TEST. Chamomile as an analgesic should be studied more in different studies.

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 Background & Objectives: Previous studies indicated that morphine consumption during pregnancy could inhibit embryos development. Present study further evaluated the effects of oral morphine consumption on the maternal and fetal portion placenta cells development in Wistar rats.

 Methods: Female Wistar rats (W: 170-200 g) were used in the present study. Morphine group were received morphine (0.05 mg/ml of tap water) after one night coupling with male rats for mating. On 14^th, 17^th days of pregnancy, the pregnant animals were killed with chloroform and the placentas and uterus were removed surgically and fixed in 10 % formalin. The fixed placentas and uterus were stained by H & E method and evaluated for their development. The thickness of layers, as well as number of the cells in both maternal and fetal parts of the placentas was determined by light microscopy and processed using MOTIC software.

 Results: The results indicated that oral consumption of morphine compared to control group, increased the thickness of the layers in maternal portion and also, increased the number of the cells in both maternal and fetal portion of the placenta.

 Conclusion: All together, oral morphine consumption may inhibit placenta cells development and disturb their natural functions. These abnormalities observed in the placenta by opioid addicted pregnancy Wistar rats.

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 Background and Objectives: Opiodergic system has important role in pain control. Origanum vulgare is a folk medicine with analgesic properties which is widely distributed in the north and northwest parts of Iran. The mechanism of therapeutic effects of Origanum vulgare is not understood. The aim of this study was to evaluate the intervention effect of opioid agonist (morphine) and antagonist (naloxone) on analgesic effects of Origanum vulgare.

 Methods: In this study 28 Male Wistar rats (200-250 g) were used (n=7). The rats were anaesthetized by ketamine (80mg /kg) and xylazine (10mg /kg) and a cannula was inserted into the left ventricle according to atlas of Paxinos characteristics using stereotaxic apparatus. The animals were allowed to recover for 5-7 days .In pilot examination, the effective dose of ORG extract determined 3µg/rat i.c.v. Rats were divided into 4 groups:Control group given saline 0.5ml.i.p/ saline 5µl.i.c.v or ORG 3µg/rat.i.c.v. other groups are morphine (2mg/kg ,i.p) and ORG3µg/rat,i.c.v , Naloxone (1mg/kg,i.p) and ORG 3µg/rat,i.c.v. The latency response of rats to thermal stimulation was recorded (30, 45, 60, 75, 90 &120 min after treatment) by Tail flick test. Repeated Measurement test and ANOVA were used to determine significant differences.

 Results: There was significant decrease in the pain threshold following the co-administration of ORG extract with naloxone in the Tail flick test. There also was significant decrease in the latency response or pain threshold 90 and 120 min after intervention in naloxone group compared with that in control group (p< 0.05).

 Conclusion: The results of this study showed that analgesic effect of aqueous extract of Origanum vulgare may be mediated, at least in part, by opioidergic system.

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 Background & Objective: It's been considered that midbrain region namely rostral ventromedial medulla (RVM) is the coring point of modulation of pain. The periaqueductal gray (PAG) matter has been documented to act as antinociceptive along with RVM. However, there are evidences demonstrating that RVM get a few connections from the cuneiformsnucleus (CnF) which might indicate CnF does have the same mechanism as PAG. Thus in this study, we tried to explore the antinociception effects of CnF and GABA_A circuits.

 Methods: Rats were anesthetized with Thiopental drug. Using the stereotaxic apparatus and Paxinos atlas, the point representing for CnF location over the scalp has been designated. One week after the surgery, rats were fully prepared for tests. Animals were put in three groups. First for control group, 0.5 µl of normal saline was injected into the CnF. Later, a few nanograms of bicucculline (as a GABA_A antagonist) were administered into the CnF, dose dependently.

 Results: From the results, it has been shown that CnF has a role in antinociception effect since the injection of bicucculline increased tail flick latency (TFL) and even further increased TFL when administered dose dependently (with high doses).

 Conclusion: According to results of current study, CnF has a significant role in pain modulation and circuits of GABAergic system also plays a key role on its antinociception effect.

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CT
 
Background & objectives: So far, various reports have been presented on the relationship between sex hormones and gender-related differences in pain and analgesia in humans and laboratory animals. The purpose of this study was to investigate the effect of testosterone hormone and spironolactone anti-androgen drug on morphine-induced analgesia in male mice using formalin test.
Methods: In this study, 80 male mice were divided into 10 groups (N=8); normal saline (control), sesame seed oil (as testosterone solvent), testosterone (5 and 10 mg/kg body weight), spironolactone, morphine, sesame seed oil + morphine, testosterone (5 and 10 mg/ kg body weight) + morphine and spironolactone + morphine. Formalin test was performed in all the mice, and data were analyzed by one-way ANOVA.
Results: The results showed that sesame seed oil + morphine (p<0.001), morphine (p<0.001), testosterone (5 mg/kg) + morphine (p<0.01) and testosterone (10 mg/kg) + morphine (p<0.001) significantly reduced acute  pain, and testosterone (5 mg/kg) (p<0.05), testosterone (10 mg/kg) (p<0.01), sesame seed oil + morphine (p<0.001), morphine (p<0.001), testosterone (5 mg/kg) + morphine (p<0.001) and testosterone (10 mg/kg) + morphine (p<0.001) significantly reduced chronic pain compared with control group. Spironolactone had no effect on pain relief in the presence and absence of morphine compared to control group.
Conclusions: It can be concluded that testosterone has analgesic effects on the chronic phase of the pain. On the other hand, spironolactone may have hyperalgesic effects due to its anti-androgenic properties.