Administration Of Morphine Sulfate Research Articles

Effect of routine abdominal drainage on postoperative pain after uncomplicated laparoscopic cholecystectomy for cholelithiasis: A randomised controlled trial

This is a prospective randomized controlled trial to investigate the effect of routine abdominal drainage on postoperative pain after uncomplicated laparoscopic cholecystectomy for cholelithiasis. This study was a single-center randomized controlled trial performed at the general surgery ward of Taleghani hospital, in Tehran, Iran, from July 2018 to October 2018. Patients were randomly divided into two parallel groups, one receiving routine abdominal drainage and the other receiving no treatment. Postoperative pain was measured by the Universal Pain Assessment Tool (UPAT) 0, 2, 4, 6, 12, and 24 h postoperatively. A total of 60 patients (30 patients in the study and control groups) were included. GLM repeated measure analysis showed a significant time*treatment effect for routine abdominal drainage in decreasing UPAT scores from baseline to 24 h after surgery (F = 4.59, df = 3.98, P-value = 0.001). Our findings demonstrated that abdominal drainage significantly reduces postoperative pain 0, 2, 4, 6, and 12 h after surgery (P-value<0.05). We also showed that abdominal drainage increases the time to first morphine sulfate administration and decreases the total dose of morphine sulfate administration (P-value<0.001). Moreover, we demonstrated that abdominal drainage decreases the average postoperative pain (P-value<0.001) and does not lead to any considerable side effects. However, 24 h after surgery, no significant pain-relieving effect was evident for abdominal drainage. In conclusion, insertion of abdominal drainage leads to decreased postoperative pain. Future studies need to investigate the optimal time for removal of the abdominal drain.This trial was prospectively registered in the Iranian Registry of Clinical Trials with a registration ID of IRCT20130706013875N2.

The contribution of morphine sulfate to the development of necrotizing enterocolitis in preterm infants: a matched casecontrol study.

Zvizdic Z, Milisic E, Jonuzi A, Terzic S, Zvizdic D. The contribution of morphine sulfate to the development of necrotizing enterocolitis in preterm infants: a matched case-control study. Turk J Pediatr 2019; 61: 513-519. The aim of the study was to determine whether morphine sulfate administration is associated with an increased risk of necrotizing enterocolitis (NEC) in preterm infants supported by mechanical ventilation due to respiratory failure. The matched case-control retrospective study was carried out at the Neonatal Intensive Care Unit (NICU) of the University Clinical Center Sarajevo, on 122 preterm infants classified into total NEC group and control group. The total NEC group was further divided into medical NEC and surgical NEC subgroups. The association between the use and duration of morphine sulfate infusion and the development of NEC was evaluated in both unadjusted and adjusted analysis. Preterm infants who developed NEC were on mechanical ventilation more frequently compared to premature infants without signs of NEC (Mann- Whitney U test; p=0.0031). A positive correlation between the frequency of receiving morphine sulfate and the development of NEC was observed (Chi square test of independence; p=0.0001). The risk of NEC in preterm infants was increased by the use of morphine sulfate. Validation of this observation in other populations is warranted.

Antagonism of orexin type-1 receptors (OX1Rs) attenuates naloxone-precipitated morphine withdrawal syndrome in rat dorsal hippocampus

Herein the effect of hippocampal orexin type-1 receptors (OX1Rs) blockade on morphine withdrawal syndrome was studied. Animals were made dependent by subcutaneous (s.c.) administration of morphine sulfate (10mg/kg) at an interval of 12h for 9 consecutive days. Thereafter, on day 10, naloxone hydrochloride (1.5mg/kg, i.p.) was injected and the somatic signs of withdrawal syndrome were monitored during a 25-min period. Two groups of animals received bilateral microinjection of either SB-334867, a selective OX1Rs antagonist, (0.5μg/0.5μl), or its vehicle into the dorsal hippocampus immediately before each morphine injection. Other groups of animals were made dependent at first and only received a single microinjection of SB-334867 or vehicle on day 10 before naloxone injection. The results showed that intra-hippocampal microinjection of SB-334867 before each morphine treatment, significantly decreased the signs of morphine withdrawal, including teeth chattering (dependent: 18.5±2.3, SB treated: 5±1, p<0.001), diarrhea (dependent: 8.7±0.6, SB treated: 4.1±0.6, p<0.001), ptosis (dependent: 33.8±3.7, SB treated: 11.6±1.1, p<0.001), and chewing (dependent: 40±2.3, SB treated: 29±2.4, p<0.01). SB-334867 did not attenuate withdrawal syndrome, when it was microinjected as a single dose immediately before naloxone injection. The present results suggest a role for orexin in naloxone-precipitated withdrawal and thus possibly morphine dependence and this effect is, at least in part, via OX1Rs in the dorsal hippocampus.

Abstract #850: Case Reports of Blunted Corticotropic and Gonadotropic Function After Acute and Chronic Administration of Morphine Sulphate

Abstract #850: Case Reports of Blunted Corticotropic and Gonadotropic Function After Acute and Chronic Administration of Morphine Sulphate

Antinociceptive and Anti-inflammatory Effects of Combined Administration of a-tocopherol and Morphine in Long Evans Rats

Background: Morphine is an opioid analgesic which is used to treat moderate to severe pain but has a number of side effects. This study is aimed to explore that combination of morphine and a-tocopherol (aT) are better analgesic as well as anti-inflammatory effect than that of morphine alone.Objective: To assess the effects of combination of morphine with a-tocopherol on pain and inflammation.Methods: This prospective experimental study was conducted in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Shahbag, Dhaka from January 2013 to December 2013. For this purpose, 15 male Long Evans rats were studied. On the basis of vitamin and drug administrations, the rats were divided into three (3) groups (5 rats in each). Control group received normal saline, one experimental group received morphine sulphate (MS) at a dose of 3 mg/kg body weight and another experimental group received combination of MS with aT at a dose of 3 mg/kg body weight and 500 mg/kg body weight, respectively. All the groups received single dose and equal volume (1 ml) through intraperitoneal route 1 hour before the test. Just one hour after administrations, they were subjected to formalin test followed by formalin induced paw edema test. The data were statistically analyzed by ANOVA followed by Bonferroni Post Hoc test.Results: Combined administration of MS and aT lowered the variables for nociceptive pain, central analgesic activity, inflammatory pain as well as inflammation than individual administration of MS.Conclusion: From this study it may be concluded that combined administration of morphine sulphate and atocopherol were more effective in lowering pain and inflammation than individual administration of morphine.Anwer Khan Modern Medical College Journal Vol. 8, No. 1: Jan 2017, P 24-29

Antinociceptive and Anti-inflammatory Effects of Combined Administration of a-Tocopherol and Morphine in Acetic Acid Induced Writhing Test

Background: Morphine represents the front line therapy for the clinical management of acute and chronic pain but has a number of side effects. So, to minimize the side effect of this tradition analgesic, this study is aimed to explore that combination of morphine and a-tocopherol (?T) are better analgesic as well as anti-inflammatory effect than that of morphine alone.Objective: to assess the effects of combination of morphine with a-tocopherol against nociceptive and inflammatory pain.Methods: This prospective experimental study was conducted in the Department of Physiology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Shahbag, Dhaka from January 2013 to December 2013. For this purpose, 15 male Long Evans rats were studied. On the basis of vitamin and drug administrations, the rats were divided into three (3) groups (5 rats in each). Control group received normal saline, one experimental group received morphine sulphate (MS) at a dose of 3 mg/kg body weight and another experimental group received combination of DS with ?T at a dose of 3 mg/kg body weight and 500 mg/kg body weight, respectively. All the groups received single dose and equal volume (1 ml) through intraperitoneal route 1 hour before the test. Just one hour after administrations, they were subjected to acetic acid induced writhing test . The data were statistically analyzed by ANOVA followed by Bonferroni Post Hoc test.Results: combined administration of MS and ?T significantly lowered (p 0.05) the variables for visceral nociceptive pain and inflammatory pain than individual administration of MS. Conclusion: from this study it may be concluded that combined administration of morphine sulphate and a-tocopherol were more effective in lowering the nociceptive and inflammatory pain than individual administration of morphine.Anwer Khan Modern Medical College Journal Vol. 7, No. 2: Jul 2016, P 20-24

Dendrosomal Curcumin Nanoformulation Attenuates Naloxone Precipitated Morphine Withdrawal Signs in Rats

Curcuminis known to possess a wide range of therapeutic and pharmacological properties as anti-inflammatory, antitumor, antinociceptive and neuroprotective agents. The recent achievements of nanotechnology illustrate a novel approach in treatment of drug abuse and addiction. Curcumin as a new candidate can be exploited for drug abuse treatment, but its low bioavailability and water solubility is the most important obstacles and limits its application. Here, curcumin was efficiently encapsulated in a nontoxic nanocarrier, labeled dendrosome, to overcome these problems. The present study is designed to investigate the effect of intraperitoneal (i.p.) administration of Dendrosomal curcumin (DNC) on the behavioral signs of morphine withdrawal syndrome. Male Wistar rats weighing 250-300 g were rendered dependent on morphine by subcutaneous (s.c.) administration of morphine sulfate (6, 16, 26, 36, 46, 56 and 66 mg/kg, 2 ml/kg) at set intervals of 24 h for 7 days. The animals received i.p. administration of DNC(12.5 mg/kg) immediately after each morphine injection. On day 8, naloxone (2 mg/ kg, i.p.) was injected and behavioral signs of morphine withdrawal were assessed for 25 min. Our results show that i.p. injection of DNC significantly decreases naloxone precipitated morphine withdrawal signs. The present study indicates that intraperitoneal administration of Dendrosomal curcumin exerts a significant effect on morphine dependency in rats.

An assessment of physical dependence following subcutaneous administration of morphine sulfate in cynomolgus monkeys

An assessment of physical dependence following subcutaneous administration of morphine sulfate in cynomolgus monkeys

Blockade of orexin type-1 receptors in locus coeruleus nucleus attenuates the development of morphine dependency in rats

The aim of this study was to evaluate the effects of orexin type-1 receptor (OX1R) antagonism in locus coeruleus (LC) nucleus on the development of morphine physical dependence in rats. Animals were rendered dependent on morphine by subcutaneous (s.c.) administration of morphine sulfate (6, 16, 26, 36, 46, 56 and 66mg/kg, 2ml/kg) at set intervals of 24h for 7 days. Immediately before each morphine administration, the animals received intra-LC administration of SB-334867 (3mM, 0.2μl), a selective orexin type-1 receptor antagonist. On day 8, naloxone (3mg/kg, i.p.) was injected and physical dependence was evaluated for 30min. Our results showed that administration of OX1R antagonist before each morphine injection significantly decreased somatic signs of naloxone-induced morphine withdrawal syndrome, including defecation, wet-dog shake, diarrhea, jumping, scratching, and teeth chattering. These results suggest that the activation of OX1R in LC nucleus might be involved in the development of morphine dependency.

Intrathecal Administration of Infumorph®vs Compounded Morphine for Treatment of Intractable Pain Using the Prometra®Programmable Pump

The intrathecal administration of morphine sulfate has become an established alternative to oral opiate therapy for the treatment of chronic pain. Currently, Infumorph(®) is the only morphine sulfate approved by the US Food and Drug Administration for continuous intraspinal administration with an infusion pump. However, in order to achieve and maintain adequate pain relief, patients may require concentrations outside of those commercially available products resulting in the use of compounded morphine. Accuracy, safety, and efficacy data related to Infumorph and compounded morphine use were collected during clinical trials of a new implantable pump. This report compares those results in a total of 154 subjects implanted with the Prometra programmable pump. The mean drug delivery accuracy using only Infumorph in 31 subjects was 100.1% and was comparable with the accuracy reported for the 71 subjects who received only compounded morphine sulfate (97.4%). The percentage of subjects free from device-related serious adverse events (DRSAEs) was similar in both groups. Compounded morphine showed statistically significant improvements in pain and disability, where Infumorph only showed a statistical improvement in pain. Dosing was higher in the compounded group. Results are also presented for a crossover group that received both types of morphine. ThePrometra system accurately delivers both Infumorph and compounded morphine with no significant differences in DRSAE rates. These results indicate that compounded morphine delivery effectively treats the chronic pain patient population. Higher doses appear to provide better pain relief; however, optimal pain relief will need to be balanced against the risk of granuloma formation.

Long-Term Follow-Up of a Novel Implantable Programmable Infusion Pump

The Prometra® Programmable Pump System (Flowonix Medical, Inc., Mt. Olive, NJ, USA) is designed for continuous intrathecal administration of morphine sulfate to treat chronic intractable pain. As a follow-up to a previous report on acute six-month data, this study evaluated the efficacy of treatment at one year and the accuracy of drug delivery throughout the study (average of 2.5 years, range 0-3.6 years). Accuracy of drug delivery was determined as the ratio of delivered-to-programmed drug volume at scheduled refill visits (monthly for the first six months and every three months thereafter). Efficacy was assessed at 12 months using the visual analog and numeric rating scales and the Oswestry Disability Index. Safety was assessed by documenting adverse events and device complications throughout the study. The mean accuracy of the Prometra pump was 97.9% and was comparable to the reported accuracy at one to six months (97.1%). After 12 months, 68% of the remaining subjects reported improvement in disability scores from baseline and more than 75% of the remaining subjects reported decreases in pain from baseline. The incidence rates of adverse events and device complications were similar to previous reports for this therapy. The Prometra pump demonstrated accurate drug delivery throughout the study and provides an effective and safe means for intrathecal administration of morphine sulfate for treatment of chronic intractable pain.

Comparison of Laparoscopically Assisted Vaginal Hysterectomy and Abdominal Hysterectomy: A Randomized Controlled Trial

Objective To compare intraoperative hemorrhage and other operative parameters after laparoscopically assisted vaginal hysterectomy (LAVH) versus total abdominal hysterectomy (TAH) for benign gynecologic conditions. Design A prospective, randomized, controlled trial. Materials and Methods Between April 2010 and March 2011, 50 Thai patients with strong indications for hysterectomy—with uterine sizes ≤16 weeks of gravid uterus and with no contraindications for open or laparoscopic surgeries—were randomly assigned for LAVH or TAH. Main Outcome Measures Intraoperative blood loss, operating time, postoperative analgesic requirements, perioperative complications, and duration of hospitalization. Results Intraoperative blood loss was significantly less in the LAVH group (median 120 mL [range 50–300]) than in the TAH group (median 250 mL [105–800]) (median difference 130 mL, p <.001, 95% confidence interval [CI] 55–200). The LAVH group required significantly less postoperative morphine sulfate administration (median 3 mg [range 0–12]) than the TAH group (15 mg [6–24]) (median difference 9 mg, p <.001, 95% CI 9–12). The hospital stay for the LAVH group (median 3 days; range 2–7) was significantly shorter than that of the TAH group (median 4 days; range 4–5) (median difference 2 days, p <.001, 95% CI 1–2). The operating time was comparable between the 2 groups (median 100 minutes; range 50–240) for the LAVH and 115 minutes (range 60–200) for the TAH group (median difference 5 minutes, p =.592, 95% CI −15–25). There were no conversions from a LAVH to a laparotomy. Conclusions The LAVH has advantages over the TAH in that in the former there is less intraoperative blood loss, less postoperative morphine requirement, and a shorter duration of postoperative hospital stays.

Histopathological and biochemical changes of morphine sulphate administration on the cerebellum of albino rats

In this study the long-term effects of morphine sulphate treatment (MST) on histopathological and biochemical changes in the cerebellum was assessed in albino rats. Normal saline (5 ml) was given orally as placebo in the control group ( n = 25). Morphine groups received morphine orally at a dose level of 5 mg/kg body weight day after day for 10, 20 and 30 days ( n = 25/group). Light microscopy revealed that the molecular layer showed vacuolation. The Purkinje cells lost their specific shaped appearance, decreased in size and numbers. The granular cells highly degenerated. Electron microscopy revealed fragmentation of the cisterns of the both types of endoplasmic reticulum, resulted in a progressive depletion of total protein contents as well as general carbohydrates in all treated groups as supported by histochemical observation. Obvious destruction of mitochondrial inner membrane and cristae mediate cell death. Also, abnormal nucleus with deformed perforated nuclear membrane and deformation of the plasma membrane with degeneration of the synapses could interpreted as a sign of necrosis. Biochemical analysis revealed that dopamine (DA) and norepinephrine (NE) were significantly decreased in four brain areas (cortex striatum, thalamus/hypothalamus, and cerebellum). In contrast, serotonin (5-HT) level was increased in these brain regions; with an exception of 5-HT on day 10 and neurotransmitter levels in the pons were unaffected. The quantitative analysis showed a significant decrease ( P < 0.05) in the diameter of Purkinje cells and in the thickness of both molecular and granular layers treated groups. Morphine sulphate induces may be a cell death or necrosis in the rat cerebellum and modulating neurotransmitter system. Our findings pointed out the risk of increased cerebellum damage due to long-term of morphine use.

Accuracy and efficacy of intrathecal administration of morphine sulfate for treatment of intractable pain using the Prometra® Programmable Pump

Intrathecal infusion pumps are increasingly used to deliver analgesics for chronic intractable pain. This trial evaluated the accuracy and efficacy of the new Prometra® Programmable Pump System for intrathecal administration of morphine sulfate to treat chronic intractable pain. One hundred and ten patients were given continuous intrathecal morphine sulfate and assessed monthly for up to six months. Accuracy was determined as the ratio of delivered to programmed drug volume (DP ratio). Efficacy was assessed using the visual analog and numeric rating scales and the Oswestry Disability Index. The mean accuracy of the Prometra pump was 97.1%, with a 90% confidence interval of 96.2-98.0%. Decreases in pain and disability were reported at 68.4% of patient visits. No unanticipated adverse events or device complications were reported. The Prometra pump provides an accurate, effective, and safe system for intrathecal administration of morphine sulfate for treatment of chronic intractable pain.

Effect of morphine on the bispectral index during isoflurane anesthesia in dogs

ObjectiveTo assess the effect of morphine on the bispectral index (BIS) in dogs during isoflurane anesthesia maintained at a constant end–tidal concentration. Study designProspective, randomized, experimental trial. AnimalsEight adult Beagle dogs, weighing between 7.1 and 9.8 kg. MethodsAnesthesia was induced with isoflurane via a face mask. Dog's tracheas were intubated and anesthesia maintained with isoflurane at a constant end–tidal concentration (e′Iso) of 1.81% for a 30–minute equilibration period. Pulmonary ventilation was controlled to normocapnia. After equilibration, baseline values were recorded prior to intravenous administration of morphine sulfate (0.5 mg kg−1) (MT) or an equal volume of saline (CT). Measurements for heart rate, systolic, diastolic and mean arterial pressure (SAP, DAP and MAP) were recorded at 10, 20, 30, 45, 60, 75, 90, 105 and 120 minutes after treatment. Bispectral index was recorded every 10 seconds for 3 minutes for each time measurement. Venous blood samples were collected at baseline, 10, 20, 30, 45, 60 and 120 minutes for determination of morphine serum concentrations. Anesthesia was discontinued after the last measurement and dogs were allowed to recover. ResultsBaseline BIS for MT and CT at 1.81%e′Iso were 63 ± 10 and 58 ± 9, respectively. Bispectral index in MT was 4–8% lower at 20, 75, 90 and 105 minutes compared with CT. There were no differences in BIS between baseline and any subsequent measurement within either MT or CT. Heart rate, SAP, MAP, and DAP decreased after morphine administration. Conclusion and clinical relevanceIntravenous administration of 0.5 mg kg−1 morphine sulfate did not cause clinically significant changes in the BIS of unstimulated dogs during isoflurane anesthesia at an e′Iso of 1.81%.

Effects of maternal oral administration of morphine sulfate on developing rat fetal cerebrum: A morphometrical evaluation

Intrauterine morphine exposure is a risk factor for neurological and behavioral deficit in children, although the precise underlying biological correlate for this is unclear. Female pregnant rats were orally treated with 0.1 mg/ml of morphine solution on the 21st day of gestation. Pregnant rats were killed on the 21st day of gestation and their fetuses were taken out and evaluated for growth and cerebral development. The fetuses were fixed and followed by dehydration through graded ethanol solutions and were then embedded and their heads were coronally sectioned through the frontal cerebral cortex. Quantitative computer-assisted morphometric study was done on the frontal cerebral cortex (FCC) which consists of cortical plate (CP), intermediate (migratory) zone (IZ) and matrix (proliferative) zone (MZ) in the rat embryos. The results showed that morphine exposure caused a significant reduction of fetal weight and crown-to-rump length in morphine exposure group. The present study showed that animals with intrauterine morphine exposure, induced by a period of reduced placental blood flow during the second week of pregnancy, demonstrate reduced both cortical thickness and the numbers of neurons in the developing fetal frontal cerebral cortex (FCC). Histomorphometric evaluation revealed that the thickness of the CP was significantly decreased in the morphine-exposed embryos. In addition, neuronal counting showed that cell proliferation in the CP was suppressed after morphine administration and that the migration of neurons from the matrix zone (MZ) to the cortex was decelerated. In conclusion, these results showed that morphine exposure during the second week of pregnancy could affect brain development in a way, which could lead to neurological and behavioral deficits in the postnatal animal.

WITHDRAWN: Effects of maternal oral administration of morphine sulfate on developing rat fetal cerebrum: A morphometrical evaluation

WITHDRAWN: Effects of maternal oral administration of morphine sulfate on developing rat fetal cerebrum: A morphometrical evaluation

Does intraosseous equal intravenous? A pharmacokinetic study

Study Objective Despite the growing popularity of intraosseous infusion for adults in emergency medicine, to date there has been little research on the pharmacokinetics of intraosseously administered medications in humans. The objective of the study was to compare the pharmacokinetics of intraosseous vs intravenous administration of morphine sulfate in adults. Methods The study followed a prospective, randomized, crossover design. Each subject was equipped with an indwelling intraosseous access device and an intravenous line. Subjects were randomized to receive a 5-mg bolus of morphine sulfate infused intraosseously or intravenously, followed by the alternate administration route 24 hours later. Serial venous blood samples (5 mL) were taken at baseline and at 13 time points over 8 hours postinfusion. Blood samples were analyzed for morphine concentration by radioimmunoassay. Pharmacokinetic parameters were calculated from the data, including maximum plasma concentration ( C max), time to maximum concentration ( T max), and area under plasma concentration-time curve (AUC), among others. Data were analyzed by analysis of variance. Results No statistically significant differences were observed between intraosseous and intravenous administration of morphine sulfate for nearly all of the pharmacokinetic parameters including C max (235 ± 107 vs 289 ± 197 ng/mL, mean ± SD, IO vs IV, respectively), T max (1.3 ± 0.5 vs 1.4 ± 0.5 minutes), and AUC (0-∞) (4372 ± 1785 vs 4410 ± 1930 ng min −1 mL −1). There was, however, a statistically significant difference in the volume of distribution in the central compartment, V d ( P = .0247), which in the opinion of the investigators was thought to be due to a minor deposition effect near the intraosseous port or in the bone marrow. Conclusion The results support the bioequivalence of intraosseous and intravenous administration of morphine sulfate in adults.

Pharmacokinetics and pharmacodynamics of morphine in llamas

To assess the pharmacokinetics and pharmacodynamics of morphine in llamas. 6 healthy adult llamas. Llamas received morphine sulfate in a randomized crossover design. In phase 1, they received IV or IM administration of morphine at 0.05 or 0.5 mg/kg, respectively; in phase 2, they received IV administration of morphine at 0.05, 0.25, or 0.5 mg/kg. Plasma morphine and morphine-6-glucuronide concentrations were determined by validated methods. Body temperature, heart rate, respiratory rate, sedation, and analgesia were assessed and compared with plasma concentrations by regression analysis. Total body clearance was similar between IV administration of morphine sulfate at 0.25 and 0.5 mg/kg (mean +/- SD, 25.3 +/- 6.9 mL/min/kg and 27.3 +/- 5.9 mL/min/kg, respectively), and linearity was demonstrated between these doses. Bioavailability of morphine following IM administration at 0.5 mg/kg was 120 +/- 30%. Body temperature and sedation increased as the dose of morphine administered increased. Heart rate was unaffected by varying doses. Respiratory rate decreased as dose increased. Analgesia was difficult to assess as a result of high individual variability. Intravenous administration of morphine at 0.25 mg/kg provided the most consistent increase in tolerance to electric stimulation. Pharmacodynamic modeling revealed a sigmoidal relationship between plasma concentration and sedation score. Morphine was characterized by a large apparent volume of distribution and high systemic clearance in llamas. A prolonged half-life was observed with IM injection. Intravenous administration of morphine sulfate at 0.25 mg/kg every 4 hours is suggested for further study.

Establishment of model of visceral pain due to colorectal distension and its behavioral assessment in rats

To establish a visceral pain model via colorectal distension (CRD) and to evaluate the efficiency of behavioral responses of CRD by measuring the score of abdominal withdrawal reflex (AWR) in rats. Thirty-eight male SD rats weighing 180-240 g were used to establish the visceral pain model. The rat was inserted intra-anally with a 7 cm long flexible latex balloon under ether anesthesia, and colorectal distensions by inflating the balloon with air were made 30 min after recovering from the anesthesia. Five AWR scores (AWR0 to AWR4) were used to assess the intensity of noxious visceral stimuli. It was regarded as the threshold of the minimal pressure (kPa). For abdominal flatting was induced by colorectal distension. A vigorous AWR to distension of the descending colon and rectum was found in 100% of the awake rats tested. The higher the pressure of distension, the higher the score of AWR. The distension pressures of 0, 2.00, 3.33, 5.33 and 8.00 kPa produced different AWR scores (P<0.05). The pain threshold of AWR was constant for up to 80 min after the initial windup (first 1-3 distensions), the mean threshold was 3.69+/-0.35 kPa. Systemic administration of morphine sulfate elevated the threshold of visceral pain in a dose-dependent and naloxone reversible manner. Scoring the AWR during colorectal distensions can assess the intensity of noxious visceral stimulus. Flatting of abdomen (AWR 3) to CRD as the visceral pain threshold is clear, constant and reliable. This pain model and its behavioral assessment are good for research on visceral pain and analgesics.