Possible involvement of β-endorphin in docosahexaenoic acid-induced antinociception

Citrulline malate (CM; CAS 54940-97-5, Stimol?) is known to limit the deleterious effect of asthenic state on muscle function, but its effect under healthy condition remains poorly documented. The aim of this longitudinal double-blind study was to investigate the effect of oral ingestion of CM on muscle mechanical performance and bioenergetics in normal rat. Gastrocnemius muscle function was investigated strictly non-invasively using nuclear magnetic resonance techniques. A standardized rest-stimulation- (5.7 min of repeated isometric contractions electrically induced by transcutaneous stimulation at a frequency of 3.3 Hz) recovery-protocol was performed twice, i.e., before (t(0)-24 h) and after (t(0)+48 h) CM (3 g/kg/day) or vehicle treatment. CM supplementation did not affect PCr/ATP ratio, [PCr], [Pi], [ATP] and intracellular pH at rest. During the stimulation period, it lead to a 23% enhancement of specific force production that was associated to significant decrease in both PCr (28%) and oxidative (32%) costs of contraction, but had no effect on the time-courses of phosphorylated compounds and intracellular pH. Furthermore, both the rate of PCr resynthesis during the post-stimulation period (VPCr(rec)) and the oxidative ATP synthesis capacity (Q(max)) remained unaffected by CM treatment. These data demonstrate that CM supplementation under healthy condition has an ergogenic effect associated to an improvement of muscular contraction efficiency.     

Induction of prolonged, continuous slow-wave sleep by blocking cerebral H₁ histamine receptors in rats

BACKGROUND AND PURPOSE

Classic H₁ histamine receptor (H₁R) antagonists are non-selective for H₁R and known to produce drowsiness. Modern antihistamines are more selective for H₁R, and are ‘non-drowsy’ presumably due to reduced permeability through the blood-brain barrier. To characterize both histaminergic sleep regulation and the central actions of antihistamines, in the present study we analysed the effect of classic and modern antihistamines on rats'' sleep using continuous i.c.v. infusions.

EXPERIMENTAL APPROACH

Effects of classic (d-chlorpheniramine; d-CPA) and second-generation (cetirizine) antihistamines on sleep were compared after i.p. injections or continuous i.c.v. infusions into rats. Fluorescent cetirizine/DBD-pz was synthesized to trace the approximate distribution of cerebral cetirizine. Furthermore, the effects of H₁R antagonists on cultured preoptic neurons were examined using calcium imaging.

KEY RESULTS

d-CPA 4 mg·kg⁻¹ i.p. increased non-rapid eye movement (REM) sleep whereas 10–40 mg·kg⁻¹d-CPA decreased non-REM sleep at dark onset time. Nocturnal i.c.v. infusions of d-CPA (10 µmol·100 µL⁻¹·10 h⁻¹) increased drowsiness but not non-REM sleep, whereas the same i.c.v. infusions of cetirizine significantly increased non-REM sleep, abolished REM sleep, and decreased wakefulness for more than 10 h. The medial preoptic area contained the greatest fluorescent labelling after i.c.v. cetirizine/DBD-pz infusions. Histamine-induced Ca²⁺ increases in medial preoptic neurons were blocked by d-CPA or cetirizine, whereas d-CPA, but not cetirizine, increased Ca²⁺ irrespective of antihistaminergic activity at ≥100 µM.

CONCLUSION AND IMPLICATIONS

The excitatory action of d-CPA may explain the seemingly inconsistent actions of d-CPA on sleep. Cerebral H₁R inhibition by cetirizine induces synchronization of cerebral activity and prolonged, continuous slow-wave sleep.     

Differential involvement of mu-opioid receptors in the rostral versus caudal nucleus accumbens in the reinforcing effects of heroin in rats: evidence from focal injections of β-funaltrexamine

RATIONALE: The nucleus accumbens is a diverse and heterogeneous structure along its rostrocaudal axis. The influence of specific subpopulations of mu-opioid receptors within the NAcc in heroin self-administration has not been documented. OBJECTIVES: This study was undertaken to investigate the involvement of subregions of the NAcc in heroin self-administration in rats. METHODS: Male rats were trained to self-administer heroin and then given beta-FNA, an irreversible mu-opioid receptor antagonist, into either the rostral or caudal portion of the NAcc. RESULTS: beta-FNA (0.25-2.5 nmol) attenuated heroin self-administration in a dose-responsive manner when given into the caudal but not rostral NAcc. The number of infusions of 18 microg of heroin self-administered was increased by 50-100%. This effect persisted for up to 17 days following administration of the highest dose. These doses of beta-FNA were found to decrease [(3)H]DAMGO binding in a dose-responsive manner and the effect was confined to the NAcc, as nearby structures such as the caudate putamen and olfactory tubercles were unaffected. The effect of beta-FNA (2.5 nmol) administration into the caudal NAcc was also assessed on the dose-effect curve for heroin. This dose apparently shifted the dose-effect curve to the right initially, followed by an apparent upward shift for up to 17 days after beta-FNA administration. CONCLUSIONS: The caudal portion of the NAcc and its output sites merit further investigation regarding the reinforcing effects of heroin.     

Stimulation of β-adrenergic receptors in the pineal gland increases the noradrenaline stores of its sympathetic nerves

Summary The administration of isoproterenol decreases the level of serotonin in the rat pineal gland and at the same time it increases pineal noradrenaline. These effects depend on the stimulation of a -adrenergic receptor because they are blocked by pretreatment of the animals with propranolol; this drug by itself does not modify either serotonin or noradrenaline levels in the pineal. The elevation of noradrenaline produced by isoproterenol is selective for the pineal because it is not observed in the salivary gland innervated by postganglionic adrenergic fibers from the same origin as pineal nerves. Pineal serotonin is stored in equilibrium in two compartments, i.e., the parenchymal cells and the adrenergic nerves and thus is most probably reduced in both sites. Since noradrenaline and serotonin are detected in pineal nerve vesicles and may coexist in them, the diminution of intravesicular serotonin, by making more storage sites available, probably determines the selective increase of pineal noradrenaline. A similar modification in the ratio of intravesicular amines as a result of the physiological stimulation of pineal -adrenergic receptors by the adrenergic neurotransmitter may explain some of the changes observed in the content of pineal amines.     

Discrete cue-conditioned alcohol-seeking after protracted abstinence: pattern of neural activation and involvement of orexin₁ receptors

BACKGROUND AND PURPOSE

The enduring propensity for alcoholics to relapse even following years of abstinence presents a major hurdle for treatment. Here we report a model of relapse following protracted abstinence and investigate the pattern of neuronal activation following cue-induced reinstatement and administration of the orexin₁ receptor antagonist SB-334867 in inbred alcohol-preferring rats.

EXPERIMENTAL APPROACH

Rats were trained to self-administer alcohol under operant conditions and divided into two groups: immediate (reinstated immediately following extinction) and delayed (extinguished and then housed for 5 months before reinstatement). Prior to reinstatement, animals were treated with vehicle (immediate n= 11, delayed n= 11) or SB-334867 (20 mg·kg⁻¹ i.p.; immediate n= 6, delayed n= 11). Fos expression was compared between each group and to animals that underwent extinction only.

KEY RESULTS

SB-334867 significantly attenuated cue-induced reinstatement in both groups. Immediate reinstatement increased Fos expression in the nucleus accumbens (NAc), infra-limbic (IL), pre-limbic (PrL), orbitofrontal (OFC) and piriform cortices, the lateral and dorsomedial hypothalamus, central amygdala and basolateral amygdala (BLA), and the bed nucleus of the stria terminalis. Following delayed reinstatement, Fos expression was further elevated in cortical structures. Concurrent with preventing reinstatement, SB-334867 decreased Fos in NAc core, PrL and OFC following immediate reinstatement. Following protracted abstinence, SB-334867 treatment decreased reinstatement-induced Fos in the PrL, OFC and piriform cortices.

CONCLUSIONS AND IMPLICATIONS

Cue-induced alcohol seeking can be triggered following protracted abstinence in rats. The effects of SB-334867 on both behaviour and Fos expression suggest that the orexin system is implicated in cue-induced reinstatement, although some loci may shift following protracted abstinence.     

Measurement of biological activity of somatotropin in hypophysectomized rats

目的：建立测定生长激素（ＧＨ）在体生物活性的方法．方法：以去垂体大鼠体重增长（ＢＷＧ）和胫骨骺软骨板宽度（ＴＥＷ）为指标，观察动物性别、给药途径、次数和周期不同对效应的影响；同时进行４ｄＢＷＧ，６ｄＢＷＧ和６ｄＴＥＷ法，测定ＧＨ的效价（平行线３×３设计）．结果：♀和♂ｓｃ和ｉｍ给药以及每日给药１次和２次的ＢＷＧ和ＴＥＷ差异无显著意义．给药６ｄ比给药４ｄ引起较大的ＢＷＧ和ＴＥＷ（Ｐ＜００５）．４ｄＢＷＧ法和６ｄＢＷＧ法在００２０－０５００ＩＵ·ｄ－１有较好的λ值（００６６０和０１７４７）和ｒ值（０９０００和０９２３７）；４ｄＢＷＧ，６ｄＢＷＧ和６ｄＴＥＷ法测得ｒｈＧＨ的效价为４６１３２，３９８２９和４８０２３ＩＵ／ａｍｐ．６ｄＢＷＧ法有较小的λ值和较低的ＡＲＦＬ值．结论：可在同一组去垂体大鼠体内同时用４ｄＢＷＧ，６ｄＢＷＧ和６ｄＴＥＷ法测ＧＨ活性，以６ｄＢＷＧ法较好．     

Effect of cyclo(Leu-Gly) on reserpine-induced hypomotility and increases in cortical β-adrenergic receptors

Previous studies have indicated that the endogenous peptide, melanotropin release inhibiting factor (MIF) and its analog cyclo(Leu-Gly) (CLG) facilitate dopamine (DA) receptor agonist binding and inhibit DA receptor supersensitivity induced by neuroleptics and opiates. The effect of CLG was tested on -adrenergic hypersensitivity induced by reserpine to ascertain whether CLG has effects on other neuronal systems besides DA. Administration of reserpine to rats induced hypomotility and enhanced binding of [³H]dihydroalprenolol (DHA) to cortical membranes. Concurrent administration of CLG blocked both the hypomotility and the enhanced [³H]DHA binding to cortical membranes. Lithium has also been shown to prevent reserpine induced hypomotility and increased cortical [³H]DHA binding. These studies suggest that CLG may be producing its effect either like lithium or by an amphetamine like action. If CLG can be shown to have lithium like activity, it could prove to be useful in the treatment of mania.     

Effects of some GABA-mimetic drugs on the antinociceptive activity of morphine and β-endorphin in rats

Summary Intracerebroventricular administration of muscimol, a potent GABA-receptor agonist, counteracted the antinociceptive effect of morphine or -endorphin in rats as measured by the tail flick method. Muscimol's activity was reversed by bicuculline. Isoguvacine, another GABA agonist, as well as nipecotic acid and guvacine, two inhibitors of neuronal and glial uptake of GABA, also antagonized morphine's antinociceptive effect. A role of the central GABA-ergic system in mediating opiate antinociception is proposed.This study was supported by C.N.R. grant no. CT 77.01401.04     

Anti-implantation activity of 2 derivatives of o-hydroxy naphthaquinones in rats

AIM:To search for female contraceptive agents. METHODS: 2-Hydroxy-3-methyl-1, 4-naphthoquinone monosemicarbazone ( HMNQS ) and 2-hydroxy-1, 4-naphthoquinone monothiosemicarbazone ( HNQTS ) were screened for anti-implantation activity in rats. RESULTS: Both compounds showed a dose-dependent activity, and HNQTS was more potent. An 100 % anti-implantation activity was observed with HNQTS 150 mg kg-1 ig . Its LD50 was found to be >2g kg-1 ig in mice. CONCLUSION: HNQTS was more potent than HMNQS for anti-implantation activity in rats.     

Changes of dopamine β-hydroxylase activity in human plasma during prolonged overactivity of the sympathetic nervous system in various diseases

Summary The activity of dopamine -hydroxylase in plasma was studied in 10 patients with various diseases accompanied by a prolonged overactivity of the sympathetic nervous system. Eight of these patients were suffering from head injury, one from tetanus and one from multiple injuries complicated by fat embolism syndrome. Plasma noradrenaline and adrenaline levels were measured concomitantly by a radioenzymatic method. It could be demonstrated that sustained increases of noradrenaline and/or adrenaline levels, which were present for several days or even weeks, were associated with a gradual decline of dopamine -hydroxylase activity. The decrease of dopamine -hydroxylase activity was more pronounced in those patients with especially high plasma catecholamine levels. In 3 patients only 13–16% of the initial dopamine -hydroxylase activity remained after an increase in the activity of the sympathetic nervous system lasting 3–4 weeks. In one of these 3 patients it could be shown that the dopamine -hydroxylase activity and the noradrenaline and adrenaline levels in plasma returned to the initial levels after complete recovery. An initial increase followed by a decline was present in these patients with the highest increases in adrenaline levels. The decline in dopamine -hydroxylase activity was not due to an increase in endogenous inhibitors, since the activity of a known amount of dopamine -hydroxylase was not reduced by adding it to a plasma in which the dopamine -hydroxylase activity was decreased.Four patients suffering from head injury without signs of an overactivity of the sympathetic nervous system served as controls. No comparable decline of the dopamine -hydroxylase activity in plasma was observable and noradrenaline and adrenaline levels were within the normal range.The results indicate that dopamine -hydroxylase activity in plasma does not provide an useful parameter of the sympatho-adrenal activity in a state of prolonged overactivity in humans. It is suggested that the decline in the plasma concentration of dopamine -hydroxylase in the latter condition may be caused by the depletion of releasable stores of this enzyme in the sympathetic nerve endings.These results were presented in part at the 19. Frühjahrstagung der Deutschen Pharmakologischen Gesellschaft Mainz, March 14–17, 1978     

Cannabinoid CB₁ receptor restrains accentuated activity of hypothalamic corticotropin-releasing factor and brainstem tyrosine hydroxylase neurons in endotoxemia-induced hypophagia in rats

It is well known that endocannabinoids play an important role in the regulation of food intake and body weight. Endocannabinoids and cannabinoid receptors are found in the hypothalamus and brainstem, which are central areas involved in the control of food intake and energy expenditure. Activation of these areas is related to hypophagia observed during inflammatory stimulus. This study investigated the effects of cannabinoid (CB₁) receptor blockade on lipopolysaccharide (LPS)-induced hypophagia. Male Wistar rats were pretreated with rimonabant (10 mg/kg, by gavage) or vehicle; 30 min later they received an injection of either LPS (100 μg/kg, intraperitoneal) or saline. Food intake, body weight, corticosterone response, CRF and CART mRNA expression, Fos-CRF and Fos-α-MSH immunoreactivity in the hypothalamus and Fos-tyrosine hydroxylase (TH) immunoreactivity in the brainstem were evaluated. LPS administration decreased food intake and body weight gain and increased plasma corticosterone levels and CRF mRNA expression in the PVN. We also observed an increase in Fos-CRF and Fos-TH double-labeled neurons after LPS injection in vehicle-pretreated rats, with no changes in CART mRNA or Fos-α-MSH immunoreactive neurons in the ARC. In saline-treated animals, rimonabant pretreatment decreased food intake and body weight gain but did not modify hormone response or Fos expression in the hypothalamus and brainstem compared with vehicle-pretreated rats. Rimonabant pretreatment potentiated LPS-induced hypophagia, body weight loss and Fos-CRF and Fos-TH expressing neurons. Rimonabant did not modify corticosterone, CRF mRNA or Fos-α-MSH responses in rats treated with LPS. These data suggest that the endocannabinoid system, mediated by CB₁ receptors, modulates hypothalamic and brainstem circuitry underlying the hypophagic effect during endotoxemia to prevent an exaggerated food intake decrease.This article is part of a Special Issue entitled ‘Central Control of Food Intake’.     

The involvement of μ- and κ- but not δ-opioid receptors in the body weight gain of suckling rats

The effects of the benzomorphan antagonist Mr 2266 and the selective -antagonist ICI 154,129 on the body weight gain of 6-day-old suckling rat pups was observed. Mr 2266 significantly reduced body weight gain in these animals, though ICI 154,129 had no affect on this variable. These findings suggest that - and - but probably not -opioic receptors are involved in the regulation of ingestive behaviours in infant rats. The results are discussed in relation to the development of opioid-receptor subtypes in the neonatal rat brain.     

Lack of involvement ofδ-opioid receptors in mediating the rewarding effects of cocaine

The non-selective opioid antagonist naltrexone and the partial agonist buprenorphine have been reported to reduce cocaine self-administration (SA) and relapse in both humans and rhesus monkeys. Data suggesting an involvement of-opioid receptors in modulating the conditioned rewarding effects of cocaine were also recently presented. In view of such findings, the present SA and place conditioning studies were conducted to examine the influence of the selective-opioid receptor antagonist naltrindole upon the rewarding effects of cocaine. Sprague-Dawley rats were trained to self-administer cocaine (1.0 mg/kg per infusion) on an FR2 schedule of reinforcement. Dose-response and antagonist testing commenced once stable rates of cocaine SA were achieved. For antagonist testing, rats received naltrindole (0.03–10.0 mg/kg, IP) 30 min prior to the start of 2-h SA sessions. SA behavior in response to cocaine delivery (0.25 and 1.0 mg/kg per infusion) was then determined. Naltrindole in doses of 0.03–3.0 mg/kg did not alter the number of cocaine infusions taken by the rats. A higher dose of naltrindole (10.0 mg/kg), which markedly depressed locomotor activity, resulted in a 16% reduction of cocaine (0.25 mg/kg per infusion) SA behavior. When SA sessions were terminated and naltrindole (1.0 mg/kg) was administered repeatedly for 3 days, no alterations in the re-acquisition of cocaine SA were seen. Place conditioning studies also failed to find an effect of naltrindole (0.1–3.0 mg/kg) on cocaine (10 mg/kg) — induced conditioned place preferences. Naltrindole, by itself, did not induce significant place conditioning. These data fail to indicate a role of-opioid receptors in modulating either the positive reinforcing or conditioned rewarding effects of cocaine. Furthermore, they suggest that the therapeutic actions of naloxone, naltrexone and buprenorphine on cocaine SA behavior may not result from the specific blockade of-opioid receptors.     

Possible involvement of ubiquitin ligase HRD1 insolubilization in amyloid β generation

Endoplasmic reticulum (ER)-associated degradation (ERAD) selectively retro-transports and degrades unfolded proteins accumulated in the ER. We have demonstrated that the ubiquitin ligase HRD1 involved in ERAD was significantly decreased in the cerebral cortex of Alzheimer's disease patients. Furthermore, the HRD1 level was negatively correlated with amyloid β (Aβ) production levels. Here we found that the HRD1 protein level decrease was due to its insolubilization. Moreover, these protein levels extracted from detergent insoluble fraction were positively correlated with those of SEL1L and Aβs (Aβ40 and Aβ42). Thus, the insolubilization-induced decrease in the HRD1 and SEL1L levels might involve in Aβ generation.     

Involvement of central β2-adrenergic, NMDA and thromboxane A2 receptors in the pressor effect of anandamide in rats

Intravenous (i.v.) injection of the endocannabinoid anandamide induces triphasic cardiovascular responses, including a pressor effect mediated via unknown central and peripheral mechanism(s). The aim of the present study was to determine the central mechanism(s) responsible for the pressor response to anandamide. For this purpose, the influence of antagonists at thromboxane A₂ TP (sulotroban, daltroban, SQ 29548), NMDA (MK-801) and β₂-adrenergic receptors (ICI 118551) on the pressor effect induced by i.v. and intracerebroventricularly (i.c.v.) administered anandamide was examined in urethane-anaesthetized rats. Anandamide (1.5–3 µmol/kg, i.v.) or its stable analogue methanandamide (0.75 µmol/kg, i.v.) increased blood pressure by 25%. Anandamide (0.03 μmol per animal i.c.v.) caused a pure pressor effect (by 20%) but only in the presence of antagonists of CB₁ and TRPV1 receptors. The effects of cannabinoids (i.v. or i.c.v.) were diminished by i.v. daltroban, sulotroban (10 μmol/kg each), and/or SQ 29548 (1 μmol/kg). The effect of anandamide i.v. was reduced by SQ 29548 (0.02 μmol per animal i.c.v.) and by the thromboxane A₂ synthesis inhibitor furegrelate i.c.v. (1.8 µmol per animal). ICI 118551, MK-801 (1 µmol/kg i.v. each), and bilateral adrenalectomy diminished the effect of anandamide i.c.v. Sulotroban (i.v.) failed to affect the response to anandamide (i.v.) in pithed rats, and anandamide and methanandamide did not bind to TP receptors in rat platelets. The present study suggests that central β₂-adrenergic, NMDA and thromboxane A₂ receptors are involved in the anandamide-induced adrenal secretion of catecholamines and their pressor effect in urethane-anaesthetized rats.     

Scutellarin protects against Aβ-induced learning and memory deficits in rats: involvement of nicotinic acetylcholine receptors and cholinesterase

Aim:

To examine the protective effects of scutellarin (Scu) on rats with learning and memory deficit induced by β-amyloid peptide (Aβ).

Methods:

Fifty male Wistar rats were randomly divided into 5 groups: control, sham operation, Aβ, Aβ+Scu, and Aβ+piracetam groups. Aβ_25–35 was injected into the lateral ventricle (10 μg each side). Scu (10 mg/2 mL) or piracetam (10 mg/2 mL was intragastrically administered per day for 20 consecutive days following Aβ treatment. Learning and memory was assessed with Morris water maze test. The protein and mRNA levels of nicotinic acetylcholine receptor (nAChR) α4, α7, and β2 subunits in the brain were examined using Western blotting and real-time PCR, respectively. The activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) in the brain and plasma were measured using Ellman''s colorimetric method.

Results:

In Aβ group, the escape latency period and first platform cross was significantly increased, and the total number of platform crossings was significantly decreased, as compared with the control and the sham operation groups. Both Scu and piracetam treatment significantly reduced the escape latency period and time to cross platform, and increased the number of platform crosses, but there were no significant differences between Aβ+Scu and Aβ+piracetam groups. In Aβ group, the protein levels of nAChR α4 and α7 subunits in the cerebral cortex were significantly decreased by 42%–47% and 58%–61%, respectively, as compared to the control and the sham operation groups. Scu treatment caused upregulation of α4 and α7 subunit proteins by around 24% and 30%, respectively, as compared to Aβ group, but there were no significant differences between Aβ+Scu and Aβ+piracetam groups. The protein level of nAChR β2 subunit had no significant difference among different groups. The mRNA levels of nAChR α4, α7, and β2 subunits were not significantly changed. In Aβ group, the activities of AChE and BuChE in the brain were significantly increased, but were significantly decreased in the plasma, as compared to the control and the sham operation groups. Scu or piracetam treatment restored the activities in brain and plasma nearly to the levels in the control group.

Conclusion:

The results suggest that Scu may rescue some of the deleterious effects of Aβ, possibly by stimulating nAChR protein translation and regulating cholinesterase activity.     

New insight into A₁ adenosine receptors in diabetes treatment

The A? adenosine receptors (A?AR), belonging to the rhodopsin-like superfamily of the G-protein-coupled receptors (GPCRs), may regulate many various cellular processes in cardiovascular, renal, and central nervous systems. In addition, since A(1)AR possesses antilipolytic properties, numerous A?AR agonists and antagonists have been developed, but only some of them with the most promising selective properties in vitro have been advanced to animal studies and clinical trials. In this review, we have summarized the studies on the utility of A?AR selective agonists and antagonists in the regulation of lipid and carbohydrate metabolism and their potential therapeutic applications in diabetes.