Behavioral, histopathological, and biochemical evaluations on the effects of cinnamaldehyde, naloxone, and their combination in morphine-induced cerebellar toxicity.

Long-term morphine use for therapeutic approaches may lead to serious side effects. Several studies have suggested opioid antagonist and antioxidant therapy for reducing adverse effects of morphine. Cinnamaldehyde has a potent anti-oxidant property. In this study, separate and combined effects of cinnamaldehyde and naloxone (an opioid receptor antagonist) on behavioral changes and cerebellar histological and biochemical outcomes were investigated after long-term morphine administration. Seventy-eight rats were divided into two major morphine-treated and morphine-untreated groups. Morphine-treated group was subdivided into seven subgroups for receiving vehicle, normal saline, cinnamaldehyde (1.25, 5, and 20 mg/kg), naloxone, and cinnamaldehyde plus naloxone before morphine. Morphine-untreated group was subdivided into six subgroups and treated with vehicle, cinnamaldehyde (1.25, 5, and 20 mg/kg), naloxone, and their combination. Chemical compounds were administered for 28 consecutive days. Behavioral tests including footprint, rotarod, and beam balance tests were employed. Histopathological and biochemical alterations of cerebellum were determined. Body and cerebellum weights, stride width, time spent on the rotarod, Purkinje cell number, thickness of molecular and granular layers, superoxide dismutase (SOD), and total antioxidant capacity (TAC) decreased as a result of administrating morphine. Morphine increased beam transverse time, malondealdehyde (MDA), tumor necrosis factor-α (TNF-α), and caspase-3 levels. Histopathological changes such as cellular vacuolation and loss were also produced as a result of treatment with morphine. Cinnamaldehyde, naloxone, and their combination treatments improved all the above-mentioned alterations induced by morphine. We concluded that cinnamaldehyde produced a neuroprotective effect through anti-oxidant, anti-inflammatory, apoptotic, and probably naloxone-sensitive opioid receptor interaction mechanisms.

Oxidative Stress Indices Changes in the Hearts of Rat Pups in Response to Maternal Buprenorphine Treatment during Gestation and Lactation.

This study aimed to assess the effects of Buprenorphine (BUP) on oxidative parameters in pups born to mothers exposed to the drug during gestation and lactation. Pregnant and lactating rats received BUP, 0.5 or 0.1 mg/kg subcutaneously for 21 and 28 days, respectively. At the end of the study, the pups were anesthetized, and the hearts were dissected out to measure oxidative stress indices, including the levels of Malondialdehyde (MDA), Nitric oxide (NO), Glutathione (GSH), and the activity of Superoxide dismutase (SOD). Our findings indicated that BUP did not alter MDA, NO, GSH levels, nor SOD activity in the cardiac tissue of pups exposed to this drug during the fetal period and through breast milk. We suggest performing additional studies to determine the association between BUP and oxidative modifications in cardiac tissues of pups born to mothers under BUP therapy during gestation and lactation.

Acute naloxone-precipitated morphine withdrawal elicits nausea-like somatic behaviors in rats in a manner suppressed by N-oleoylglycine.

RATIONALE: Acute naloxone-precipitated morphine withdrawal (MWD) produces a conditioned place aversion (CPA) in rats even after one or two exposures to high-dose (20 mg/kg, sc) morphine followed 24-h later by naloxone (1 mg/kg, sc). However, the somatic withdrawal reactions produced by acute naloxone-precipitated MWD in rats have not been investigated. A recently discovered fatty acid amide, N-oleoylglycine (OlGly), which has been suggested to act as a fatty acid amide hydrolase (FAAH) inhibitor and as a peroxisome proliferator-activated receptor alpha (PPARα) agonist, was previously shown to interfere with a naloxone-precipitated MWD-induced CPA in rats. OBJECTIVES: The aims of these studies were to examine the somatic withdrawal responses produced by acute naloxone-precipitated MWD and determine whether OlGly can also interfere with these responses. RESULTS: Here, we report that following two exposures to morphine (20 mg/kg, sc) each followed by naloxone (1 mg/kg, sc) 24 h later, rats display nausea-like somatic reactions of lying flattened on belly, abdominal contractions and diarrhea, and display increased mouthing movements and loss of body weight. OlGly (5 mg/kg, ip) interfered with naloxone-precipitated MWD-induced abdominal contractions, lying on belly, diarrhea and mouthing movements in male Sprague-Dawley rats, by both a cannabinoid 1 (CB1) and a PPARα mechanism of action. Since these withdrawal reactions are symptomatic of nausea, we evaluated the potential of OlGly to interfere with lithium chloride (LiCl)-induced and MWD-induced conditioned gaping in rats, a selective measure of nausea; the suppression of MWD-induced gaping reactions by OlGly was both CB1 and PPARα mediated. CONCLUSION: These results suggest that the aversive effects of acute naloxone-precipitated MWD reflect nausea, which is suppressed by OlGly.

Oleoyl glycine: interference with the aversive effects of acute naloxone-precipitated MWD, but not morphine reward, in male Sprague-Dawley rats.

RATIONALE: Oleoyl glycine (OlGly), a recently discovered fatty acid amide that is structurally similar to N- acylethanolamines, which include the endocannabinoid, anandamide (AEA), as well as endogenous peroxisome proliferator-activated receptor alpha (PPARα) agonists oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), has been shown to interfere with nicotine reward and dependence in mice. OBJECTIVES AND METHODS: Behavioral and molecular techniques were used to investigate the ability of OlGly to interfere with the affective properties of morphine and morphine withdrawal (MWD) in male Sprague-Dawley rats. RESULTS: Synthetic OlGly (1-30 mg/kg, intraperitoneal [ip]) produced neither a place preference nor aversion on its own; however, at doses of 1 and 5 mg/kg, ip, it blocked the aversive effects of MWD in a place aversion paradigm. This effect was reversed by the cannabinoid 1 (CB1) receptor antagonist, AM251 (1 mg/kg, ip), but not the PPARα antagonist, MK886 (1 mg/kg, ip). OlGly (5 or 30 mg/kg, ip) did not interfere with a morphine-induced place preference or reinstatement of a previously extinguished morphine-induced place preference. Ex vivo analysis of tissue (nucleus accumbens, amygdala, prefrontal cortex, and interoceptive insular cortex) collected from rats experiencing naloxone-precipitated MWD revealed that OlGly was selectively elevated in the nucleus accumbens. MWD did not modify levels of the endocannabinoids 2-AG and AEA, nor those of the PPARα ligands, OEA and PEA, in any region evaluated. CONCLUSION: Here, we show that OlGly interferes with the aversive properties of acute naloxone-precipitated morphine withdrawal in rats. These results suggest that OlGly may reduce the impact of MWD and may possess efficacy in treating opiate withdrawal.

Naloxegol, an opioid antagonist with reduced CNS penetration: Mode-of-action and human relevance for rat testicular tumours.

Naloxegol is an opioid antagonist which has been developed for the treatment of patients with opioid induced constipation. In the nonclinical safety program naloxegol was shown to have a very benign toxicity profile. In the rat, but not the mouse, 2-year carcinogenicity study a change in tumour pattern with an increase in testicular Leydig cell tumours (LCT) was observed after dosing at high (supra-pharmacological) concentrations. To establish the basis of the increase in LCT and to assess its potential relevance to humans, studies to exclude and potentially identify mode-of-action (MoA) were performed. A genotoxic mechanism was ruled out following negative results in the Ames, mouse lymphoma, and micronucleus assays. An effect on androgen metabolism was excluded since the treatment of rats with naloxegol for 14days did not result in any induction of CYP protein levels. It was demonstrated that administration of centrally restricted opioid antagonists naloxegol or methylnaltrexone at high doses induced an increase in LH release with no clear increase in testosterone, in contrast to the centrally acting opioid antagonist naloxone, which showed marked increases in both LH and testosterone. LCT due to increased LH stimulation is common in rats but not documented in humans. Collectively, the lack of genotoxicity signal, the lack of androgen effect, the increase in LH secretion in rats, which is no considered to be relevant for LCT formation in humans, and high margins to clinical exposures, the observed increase in LCT in the rat is not expected to be clinically relevant.

Pioglitazone potentiates development of morphine-dependence in mice: possible role of NO/cGMP pathway.

Peroxizome proliferator-activated receptor gamma (PPARγ) is highly expressed in the central nervous system where it modulates numerous gene transcriptions. Nitric oxide synthase (NOS) expression could be modified by simulation of PPARγ which in turn activates nitric oxide (NO)/soluble guanylyl-cyclase (sGC)/cyclic guanosine mono phosphate (cGMP) pathway. It is well known that NO/cGMP pathway possesses pivotal role in the development of opioid dependence and this study is aimed to investigate the effect of PPARγ stimulation on opioid dependence in mice as well as human glioblastoma cell line. Pioglitazone potentiated naloxone-induced withdrawal syndrome in morphine dependent mice in vivo. While selective inhibition of PPARγ, neuronal NOS or GC could reverse the pioglitazone-induced potentiation of morphine withdrawal signs; sildenafil, a phosphodiesterase-5 inhibitor amplified its effect. We also showed that nitrite levels in the hippocampus were significantly elevated in pioglitazone-treated morphine dependent mice. In the human glioblastoma (U87) cell line, rendered dependent to morphine, cAMP levels did not show any alteration after chronic pioglitazone administration while cGMP measurement revealed a significant rise. We were unable to show a significant alteration in neuronal NOS mRNA expressions by pioglitazone in mice hippocampus or U87 cells. Our results suggest that pioglitazone has the ability to enhance morphine-dependence and to augment morphine withdrawal signs. The possible pathway underlying this effect is through activation of NO/GC/cGMP pathway.

Diabetogenic effect of a series of tricyclic delta opioid agonists structurally related to cyproheptadine.

The unexpected observation of a hyperglycemic effect of some tricycle-based delta opioid receptor (DOR) agonists led to a series of studies to better understand the finding. Single administration of two novel tricyclic DOR agonists dose dependently elevated rat plasma glucose levels; 4-week toxicology studies confirmed the hyperglycemic finding and further revealed pancreatic ß-cell hypertrophy, including vacuole formation, as well as bone dysplasia and Harderian gland degeneration with regeneration. Similar diabetogenic effects were observed in dog. A review of the literature on the antiserotonergic and antihistaminergic drug cyproheptadine (CPH) and its metabolites revealed shared structural features as well as similar hyperglycemic effects to the present series of DOR agonists. To further evaluate these effects, we established an assay measuring insulin levels in the rat pancreatic ß-cell-derived RINm5F cell line, extensively used to study CPH and its metabolites. Like CPH, the initial DOR agonists studied reduced RINm5F cell insulin levels in a concentration-dependent manner. Importantly, compound DOR potency did not correlate with the insulin-reducing potency. Furthermore, the RINm5F cell insulin results correlated with the diabetogenic effect of the compounds in a 5-day mouse study. The RINm5F cell insulin assay enabled the identification of aryl-aryl-amine DOR agonists that lacked an insulin-reducing effect and did not elevate blood glucose in repeated dosing studies conducted over a suprapharmacologic dose range. Thus, not only did the RINm5F cell assay open a path for the further discovery of DOR agonists lacking diabetogenic potential but also it established a reliable, economical, and high-throughput screen for such potential, regardless of chemotype or target pharmacology. The present findings also suggest a mechanistic link between the toxicity observed here and that underlying Wolcott-Rallison Syndrome.

Economic analysis of alvimopan in North American Phase III efficacy trials.

PURPOSE: The economic effect of the use of alvimopan in four randomized, double-blind, placebo-controlled, Phase III, North American efficacy trials was analyzed. METHODS: Patients were eligible for the study if they were 18 years or older, were undergoing laparotomy for partial small or large bowel resection with primary anastomosis, and were scheduled for postoperative pain management with opioid-based i.v. patient-controlled analgesia. Patients analyzed in the North American Phase III trials received placebo or alvimopan 12 mg orally before surgery. Doses were administered twice daily beginning the day after surgery until hospital discharge or for a maximum of 15 doses. RESULTS: Compared with placebo, alvimopan was associated with a significantly shorter mean time to gastrointestinal (GI) recovery and a significantly shorter mean time to a written discharge order. Alvimopan was also associated with a mean hospital length of stay (LOS) of one full day less than placebo. The mean cost of alvimopan based on a mean of 8.9 12-mg doses was $558.00; the alvimopan cost at the upper limit of allowed dosing was $937.50. Combining the alvimopan and hospital costs for each patient, total costs for the alvimopan group were estimated to be lower than for the placebo group. CONCLUSION: In a post hoc analysis, alvimopan was associated with significantly faster upper and lower GI recovery after bowel resection and a mean LOS reduction of one day compared with placebo. The mean estimated hospital cost was $879-$977 less for patients who received alvimopan compared with placebo. The base-case and sensitivity analyses suggest that, on average, the use of alvimopan compared with placebo may have a cost-saving effect in the hospital setting.

The influence of different sub-type delta opioid receptors in nerve growth factor-induced neuronal differentiation in rat pheochromocytoma PC12 cell.

The impairment of neuronal differentiation for long-term opioid drug-exposed infants is a serious problem and there are several speculated mechanisms. We have previously reported that altering the endogenous delta opioid receptor by long-term interaction with its antagonist augmented the nerve growth factor (NGF)-induced neuronal differentiation of rat pheochromocytoma PC12 cells. In this study using subtype-specific antagonist, we present data showing further that type 2 delta opioid receptor (delta(2)-DOR) is the receptor on the PC12 cells participating in the progression of neuronal differentiation upon NGF-stimulation. Unlike the delta(2)-DOR, alteration of type 1 DOR (delta(1)-DOR) activity by delta(1)-DOR-specific antagonist appeared to be toxic for the PC12 cells. The different influence of the subtypes of delta opioid receptors in the neuronal differentiation of the PC12 cells suggests that each subtype of opioid receptor may trigger different biological activities in vivo.

Opposite modulation of opiate withdrawal behaviors on microinfusion of a protein kinase A inhibitor versus activator into the locus coeruleus or periaqueductal gray.

Chronic opiate administration upregulates the cAMP pathway in the locus coeruleus (LC). This adaptation is thought to increase the electrical excitability of LC neurons and contribute to the dramatic increase in LC firing induced by opioid receptor antagonists in opiate-dependent animals. The goal of the present study was to evaluate directly a role of the cAMP pathway in opiate withdrawal behaviors by studying, in vivo, whether withdrawal is influenced by intra-LC infusion of compounds known to activate or inhibit protein kinase A (PKA). Infusions into amygdala or periaqueductal gray (PAG) were studied for comparison. In one series of experiments the effect of intra-LC, intra-amygdala, or intra-PAG infusions of the PKA inhibitor Rp-cAMPS on naloxone-precipitated withdrawal from morphine was examined. Intra-LC infusions of Rp-cAMPS significantly attenuated several prominent behavioral signs of morphine withdrawal. Intra-PAG infusions of Rp-cAMPS also significantly attenuated opiate withdrawal behaviors, although different behaviors were affected. In contrast, intra-amygdala infusions of Rp-cAMPS were without significant effect. In a second series of experiments the effect of intra-LC or intra-PAG infusions of the PKA activator Sp-cAMPS on behavior in nondependent drug-naive animals was determined. Sp-cAMPS infusions into either brain region induced a quasi-withdrawal syndrome, but the observed behaviors differed between the two groups. Analysis of the phosphorylation state of tyrosine hydroxylase, a well characterized substrate for PKA, confirmed the ability of Rp-cAMPS and Sp-cAMPS to inhibit and activate, respectively, PKA activity in vivo. Together, these data provide direct evidence for involvement of the cAMP-PKA system in the LC, as well as in the PAG, in opiate withdrawal and withdrawal-related behaviors.