Effect of neurotropin on hyperalgesia induced by prostaglandin E2, naloxone, melatonin and dark condition in mice

Subcutaneous injection of formaldehyde into mouse hind paw elicited pain responses consisting of licking or biting of the paw, which were observed biphasically. The first and second phases were enhanced by melatonin and melatonin, naloxone, prostaglandin E2, respectively. Mice kept in the dark also exhibited hyperalgesic response. When neurotropin was injected intraperitoneally 30 min prior to those treatments, hyperalgesia was suppressed to the control level. Aspirin inhibited only the second hyperalgesic phase.     

Etorphine induction of analgesia and catatonia in the rat: Systemic or intracranial injection

Etorphine was injected into the rat either intraperitoneally (i.p.), in the periaqueductal gray (PAG) region of the midbrain, or in the cerebellum (CB). The flinch-jump technique was used to measure analgesia and the bar test to assess catatonia. Etorphine doses were 5, 10, 50 or 100 μg/kg (i.p.). The doses of etorphine administered to the PAG were 0.1, 1.0, 2.0 or 3.0 μg. The dose of etorphine administered to the cerebellum was 2.0 μg. The effective doses into the PAG for producing both analgesia and catatonia were about 15 times less than the intraperitoneal doses, suggesting central mediation of these actions, involving the PAG and perhaps other central neural sites. Injection of 2.0 μg etorphine into the cerebellum did not cause analgesia or catatonia. There was a high correlation between the production of analgesia and of catatonia suggesting a common factor in these actions, at least as measured in this experiment.     

We are the researched,the researchers,and the discounted: The experiences of drug user activists as researchers

In this commentary, activists from Urban Survivors Union, the United States national drug users union, discuss our experiences conducting research on methadone clinic adoption of relaxed SAMHSA guidelines during the COVID-19 epidemic. In particular, we focus on our interactions with academic researchers as a grassroots organization of criminalized people designing our own research. We describe the challenges we navigated to retain decision making powers over the research question, data analysis and interpretation, and dissemination. We find that our collaborations with academic researchers are often complicated by power imbalances and structural issues. In our experience as directly impacted people, even community based participatory research (CBPR) often sidelines us. Our eventual research approach demonstrates how our process transcends CBPR by becoming community driven research (CDR). We suggest several changes to the research process in order to propagate this model.     

Comparison of gamma-glutamyl transferase induction by phenobarbital in the rat, guinea pig and rabbit

Serum and hepatic γ-glutamyl transferase (GGT) activities were correlated with the microsomal markers cytochrome P-450 and aminopyrine N-demethylase after i.p. injection of phenobarbital (PB) to rats, guinea pigs and rabbits. The response to PB in the regimen employed was greatest in the rabbit and least in the guinea pig. Great disparities were observed in the microsomal protein contents following PB administration to the three species, masking the responses of the other indices when these were related to protein contents rather than to tissue weights. The increased hepatic GGT activities in PB-treated guinea pigs and rabbits were reflected in increased serum activities of this enzyme; the hepatic and serum GGT activities showed an excellent correlation with cytochrome P-450 and aminopyrine N-demethylase activities, supporting the view that the changes in GGT activity were related to enzyme induction. Although hepatic GGT activity in PB-treated rats also showed good correlation with enzyme induction indices, activity of this enzyme in rat serum was undetectable in control and PB-treated animals. Analysis of ribosome-free microsomal proteins by sodium dodecylsulfate (SDS)-polyacrylamide gel electrophoresis confirmed the marked increase in three bands in the PB-treated rat, but quite different changes were noted in the guinea pig and the rabbit. Our results extend knowledge about the heterogeneous response to PB shown by different animal species. The data provide further evidence that GGT is a PB-inducible enzyme, and suggest that the rabbit is the best model for elucidating the relationship between enzyme induction and GGT activity occurring in several human clinical situations.     

Behavioral effects of intrahippocampal injections of clonidine, yohimbine and salbutamol in the rat

Intrahippocampal injections of adrenergic drugs, clonidine (an alpha 2-agonist), yohimbine (an alpha 2-antagonist), and salbutamol (a beta 2-agonist) were performed in the awake rat. The injection of a high dose of clonidine caused a depression in locomotion in the open-field. Yohimbine partially antagonized the clonidine-induced hypomotility. The intrahippocampal injection of salbutamol had no effect on ambulatory behavior of the rat. These results suggest that the role played by the anterodorsal hippocampus in modifying behavior in novel situations is dependent on the specific sub-population of adrenoceptors that is stimulated.     

Triazolam-induced sleep in the rat: influence of prior sleep,circadian time,and light/dark cycles

Rats entrained to 12-h on /12-h off light schedule and injected with triazolam 0.4 mg/kg at the mid-point of their activity phase (6 h after lights out: circadian time = CT-18) had a stronger hypnotic response than animals free-running in constant dark injected at the equivalent circadian time. In contrast, entrained rats injected 5 h after lights on (CT-5) showed increased wake after injection relative to baseline, largely due to REM sleep inhibition. Hypnotic efficacy was found to be inversely related to prior accumulated sleep. During the 6 h before injection, entrained rats injected at CT-18 slept significantly less than the free-running rats, which in turn slept significantly less than entrained rats injected at CT-5. Taken together, the results suggest that the amount of prior sleep was a more important influence on the response to triazolam than either light/dark per se or circadian phase. Methodologically, automated sleep scoring was found to be an efficient method for examining drug effects, particularly when corroborated by concurrent independent physiological variables and spectral analysis.     

Metallothionein induction in rat liver by dietary restriction or exercise and reduction of exercise-induced hepatic lipid peroxidation

Metallothioneins (MTs) occur throughout the animal kingdom and they are induced in vivo by metals, hormones, cytotoxic agents, and some kind of stress. It is well known that various stresses such as starvation and immobilization can induce MT synthesis in animal tissues, but the influence of dietary restriction is unknown. The MT levels in the liver increased by food-deprivation and then decreased by refeeding, and a long period of starvation down-alters hepatic MT levels. When the stress is intensified, the induced quantity of hepatic MT is reduced. It became clear that hepatic MT concentrations are controlled within a two fold limit when stressed by dietary restriction. MT was also induced in rat liver at recovery stage following an exhaustive running exercise, and thionein was synthesized first and then zinc bound to the protein. The half-life of hepatic MT induced by exercise (which is a nonmetallic inducer) was estimated at 5.2 h. Preinduced MT markedly suppressed exercise-induced lipid peroxidation in rat liver.     

Pharmacological inhibition of forskolin-stimulated adenylate cyclase activity in rat brain by melatonin, its analogs, and diazepam

Preincubation of rat forebrain membranes for 30-60 min with micromolar concentrations of the pineal hormone, melatonin, significantly inhibited forskolin-stimulated adenylate cyclase (AC) activity. Melatonin had an EC25 (concentration which inhibited AC activity by 25%) of 600 microM and caused a maximal inhibitory effect of approximately 30% at a concentration of 1000 microM. A comparison of the effects of melatonin and its analogs, 6-chloromelatonin and 2-iodomelatonin, in the striatum revealed that these halogenated drugs were 2-3 times more potent than melatonin in inhibiting AC activity. The EC25 values were 611, 226 and 189 microM for melatonin, 6-chloromelatonin and 2-iodomelatonin respectively. The receptor antagonists phentolamine (alpha-adrenergic), propranolol (beta-adrenergic), and metergoline (serotonergic) did not block the effect of melatonin in forebrain membranes. The central-type benzodiazepine (BZ) antagonist, Ro 15-1788 (flumazenil), also failed to block the inhibitory effects of melatonin, and the benzodiazepines, diazepam and Ro 5-4864, on AC activity. Evidence that inhibition of adenylate cyclase activity may be involved in the prevention of seizures suggests that the reported anticonvulsant effect of large doses of melatonin may be due to this mechanism. The greater potency of the halogenated melatonin analogs in inhibiting AC suggests that further study of their potential usefulness as anticonvulsants would be worthwhile.     

Phospholipase D-dependent and -independent p38MAPK activation pathways are required for superoxide production and chemotactic induction, respectively, in rat neutrophils stimulated by fMLP

Mitogen-activated protein kinase (MAPK)-mediated signal transduction pathways convert signals by extracellular stimulation into a variety of cellular functions. However, the roles of MAPKs in neutrophils are not well understood. To elucidate the temporal roles of p38MAPK during rat neutrophil activation stimulated by N-formyl-methionyl-leucyl-phenylalanine (fMLP), we examined the kinetics of this enzyme and the role of p38MAPK related to neutrophil functions (superoxide production and chemotaxis). SB203580, a potent and specific inhibitor of p38MAPK, significantly depressed both superoxide production and chemotaxis. Ethanol and 1-butanol, inhibitors of phospholipase D (PLD), suppressed p38MAPK activation in neutrophils under conditions (1 microM fMLP for 5 min) that stimulated superoxide production; and they significantly depressed superoxide production in rat neutrophils stimulated by fMLP. However, neither inhibitor had any effect on the activation of p38MAPK under the conditions (10 nM fMLP for 60 min) that gave optimal chemotaxis. These results indicate that multiple signaling pathways were involved in stimulating p38MAPK and that p38MAPK played different roles in regulating neutrophil function depending on the conditions for stimulation with fMLP. In addition, the activation of p38MAPK occurred dependent on or independent of PLD activation in neutrophils stimulated with fMLP.     

Increase of brain endocannabinoid anandamide levels by FAAH inhibition and alcohol abuse behaviours in the rat

RATIONALE: A major clinical concern with the use of cannabinoid receptor 1 (CB1) direct agonists is that these compounds increase alcohol drinking and drug abuse-related behaviours. As an alternative approach, CB1-receptor-mediated activity can be facilitated by increasing anandamide levels with the use of hydrolase fatty acid amide hydrolase (FAAH) inhibitors. OBJECTIVE: Using the selective FAAH inhibitor URB597, we investigated whether activation of the endogenous cannabinoid tone increases alcohol abuse liability, as what happens with the CB1 receptor direct agonists. MATERIALS AND METHODS: URB597 was tested on alcohol self-administration in Wistar rats and on homecage alcohol drinking in genetically selected Marchigian Sardinian alcohol-preferring (msP) rats. In Wistar rats, URB597 effects on alcohol-induced anxiety and on stress-, yohimbine- and cue-induced reinstatement of alcohol seeking were also evaluated. For comparison, the effect of the CB1 receptor antagonist rimonabant on ethanol self-administration was also tested. RESULTS: Under our experimental condition, intraperitoneal (IP) administration of URB597 (0.0, 0.3 and 1.0 mg/kg) neither increased voluntary homecage alcohol drinking in msP rats nor facilitated fixed ratio 1 and progressive ratio alcohol self-administration in nonselected Wistars. In the reinstatement tests, the compound did not have effects on cue-, footshock stress- and yohimbine-induced relapse. Conversely, URB597 completely abolished the anxiogenic response measured during withdrawal after an acute IP administration of alcohol (3.0 g/kg). Rimonabant (0.0, 0.3, 1.0 and 3.0 mg/kg) significantly reduced ethanol self-administration. CONCLUSIONS: Results demonstrate that activation of the endocannabinoid anandamide system by selective inhibition of FAAH does not increase alcohol abuse risks but does reduce anxiety associated to alcohol withdrawal. We thus can speculate that medication based on the use of endocannabinoid system modulators such as URB597 may offer important advantages compared to treatment with direct CB1 receptor activators.     

Generation of the melatonin endocrine message in mammals: a review of the complex regulation of melatonin synthesis by norepinephrine,peptides, and other pineal transmitters

Melatonin, the major hormone produced by the pineal gland, displays characteristic daily and seasonal patterns of secretion. These robust and predictable rhythms in circulating melatonin are strong synchronizers for the expression of numerous physiological processes in photoperiodic species. In mammals, the nighttime production of melatonin is mainly driven by the circadian clock, situated in the suprachiasmatic nucleus of the hypothalamus, which controls the release of norepinephrine from the dense pineal sympathetic afferents. The pivotal role of norepinephrine in the nocturnal stimulation of melatonin synthesis has been extensively dissected at the cellular and molecular levels. Besides the noradrenergic input, the presence of numerous other transmitters originating from various sources has been reported in the pineal gland. Many of these are neuropeptides and appear to contribute to the regulation of melatonin synthesis by modulating the effects of norepinephrine on pineal biochemistry. The aim of this review is firstly to update our knowledge of the cellular and molecular events underlying the noradrenergic control of melatonin synthesis; and secondly to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis. This information reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism. This also clarifies the role of these various inputs in the seasonal variation of melatonin synthesis and their subsequent physiological function.     

Neu-P11抑制高糖高脂喂养大鼠体重的增长和脂肪的异位沉积

目的观察Neu-P11(一种新型的褪黑素受体激动剂),对高糖高脂喂养的SD大鼠体重及脂肪的影响。方法高糖高脂喂养SD大鼠5个月,建立肥胖动物模型。分组给予腹腔注射生理盐水、褪黑素(4mg/kg)、Neu-P11(10mg/kg),每周监测体重和食物摄入量。实验末处死动物,分离腹部脂肪组织并称重。结果与生理盐水组比较,Neu-P11或褪黑素处理组肥胖大鼠体重的增长明显受到抑制,腹部脂肪减少,各组相对摄食(每100g体重摄食量)无明显差异。结论Neu-P11能降低高糖高脂喂养大鼠的体重增长和脂肪沉积。     

The induction of amyloid precursor protein and alpha-synuclein in rat hippocampal astrocytes by diethyldithiocarbamate and copper with or without glutathione

alpha-Synuclein is the major component of Lewy bodies. Its aggregation can be accelerated by copper, iron, or beta-amyloid (Abeta) and has been thought to provide a nucleation center during the formation of amyloid plaques. The main structural component of amyloid plaque is Abeta, which is derived from a larger protein, amyloid precursor protein (APP). Xenobiotics have been implicated in the etiology of the neurodegenerative disease. Mechanisms of diethyldithiocarbamate (DDC) neurotoxicity involve copper chelation and interactions with SH groups resulting in oxidative stress. In this study, rat hippocampal astrocytes were treated with DDC (75 microM), CuCl(2) (0.2 microM), or DDC (75 microM) plus CuCl(2) (0.2 microM) for 1h. Cells were allowed to recover with or without 10 mM GSH. Results showed an increase of APP and alpha-synuclein production occurring in a time-dependent manner. At 4 h post-treatment, cells contained small positively stained material deposited throughout the cytosol for APP and by 8 h post-treatment increases were seen in both APP and alpha-synuclein. Immunoblots supported immunocytochemical results. Glutathione (GSH) decreased the accumulation of these proteins at 8 h post-treatment.     

Rapid induction and quantitation of morphine dependence in the rat by pellet implantation

Four schedules of subcutaneous morphine pellet implantation were developed to render rats rapidly physically dependent on morphine. The schedules included implantation of four morphine pellets over a 3-day period (schedule 1), six morphine pellets over a 3-day period (schedule 2), six pellets over a 7-day period (schedule 3), and ten pellets over a 10-day period (schedule 4). Each morphine pellet contained 75 mg of morphine base. The degree of morphine dependence was quantitated by determining the median effective dose (ED₅₀) of naloxone required to induce the stereotyped jumping response. Hypothermia and weight loss, during abrupt and naloxone-induced withdrawal, were also measured. Rats on schedule 4 exhibited a high degree of dependence on morphine as evidenced by an extremely low naloxone ED₅₀ for the precipitated withdrawal jumping response, whereas schedules 1 and 2 produced a low degree of dependence as shown by high naloxone ED₅₀'s. Further evidence for a high degree of physical dependence on morphine is schedule 4 rats was indicated by their greater loss in body weight and greater hypothermic response after abrupt and after naloxone precipitated withdrawal compared with these responses in the rats in the other three schedules. A correlation was found to exist between naloxone ED₅₀ for the jumping response, body weight loss, and hypothermia observed during naloxone-induced withdrawal in morphine-dependent rats. These studies suggest that the implantation of four morphine pellets in the rat produces a mild degree of dependence and that caution should be exercised when making generalized conclusions about the biochemical correlations involved when four or less number of pellets, each containing 75 mg of morphine base, are used to induce morphine dependence in the rat.     

The effects on thermoregulation of intracerebroventricular injections of acetylcholine,pilocarpine, physostigmine,atropine and hemicholinium in the rat

The effects of intracerebroventricular (i.c.v.) injections of acetylcholine, pilocarpine, physostigmine, atropine and hemicholinium on the thermoregulatory functions of rats to ambient temperatures (T_a) of 8 and 22°C were assessed. Intracerebroventricular injections of acetylcholine, pilocarpine and physostigmine each produced a dose-dependent hypothermia in rats at both T_a of 8 and 22°C. The hypothermia in response to either acetylcholine, pilocarpine or physostigmine was brought about by both decreased metabolic heat production and cutaneous vasodilatation. Furthermore, the hypothermia induced by these agents was greatly reduced by pretreatment of animals with a small dose of atropine (2 μg i.c.v.). In addition, intracerebroventricular injection of a larger dose of atropine (5–7 μg) and hemicholinium (5–10 μg) each produced a dose-dependent hypothermia at both T_a of 8 and 22°C. The hypothermia in response to atropine and hemicholinium was brought about solely by a reduction in metabolic heat production. Thus, in the rat, intracerebroventricular injection of acetylcholine, pilocarpine, physostigmine, atropine (5–7 μg) and hemicholinium each produces the hypothermie effects, and intracerebroventricular injection of atropine (2 μg; which had no effects on rectal temperature at this dose) blocks the hypothermie effects induced by acetylcholine, pilocarpine and physostigmine in the rat.