中脑导水管周围灰质微量注射吗啡的免疫调节作用(英文)

目的:研究吗啡经大鼠中脑导水管周围灰质对免疫系统的影响.方法;大鼠PAG埋植铜管,经此管微量注射吗啡后观察大鼠细胞因子IL-2,IL-6,TNF及NK活力的变化.结果:PAG微量注射吗啡(0,5 μL,3672 ng)显著促进IL-2,TNF-β的产生及T细胞的增殖,对NK细胞的杀伤活性却有抑制作用,这些促进或抑制作用都能被PAG预先微量注射纳洛酮所阻断,对大鼠脾脏巨噬细胞的IL-6及TNF-α的产生都无影响.结论:吗啡通过PAG的阿片受体影响免疫功能,并且对不同的免疫活性细胞的影响各不相同.     

Effect on the nociceptive threshold and EEG activity in the rat of morphine injected into the medial thalamus and the periaqueductal gray

Rats were chronically implanted with EEG electrodes and. either microinjection cannulae aimed at the medial thalamus (MT) and periaqueductal gray (PAG), or a spinal catheter. Morphine sulphate injected intraperitoneally produced both analgesia, as measured by the tail flick and pinch-agitation tests, and episodes of high-voltage slow-wave activity (HVSA) in the EEG. Morphine injected into the MT produced HVSA but not analgesia. Conversely, morphine injected into PAG sites or into the lumbar subarachnoid space produced analgesia but did not alter EEG activity. These data suggest that the MT may mediate the EEG alterations produced by systemically administered morphine. They also indicate that analgesia (as measured by the tests employed) and HVSA are entirely independent actions of morphine mediated by different neuroanatomical substrates. The functional significance of the cortical HVSA produced by morphine and its mechanism of production are discussed.     

Chronic running wheel activity attenuates the antinociceptive actions of morphine and morphine-6-glucouronide administration into the periaqueductal gray in rats

Chronic exercise in a running wheel increases baseline pain sensitivity while attenuating the antinociceptive effects of peripherally administered opiate agonists in laboratory rodents. To determine if these effects are due to exercise-induced changes in the central nervous system (CNS) or an artifact of exercise-induced alterations in peripheral physiology, the present study evaluated the antinociceptive actions of centrally administered opiate agonists in active and inactive female rats. Rats were implanted with cannula into the right periaqueductal gray (PAG) area of the midbrain. After the completion of the surgery, the animals were allowed ad libitum access to running wheels or housed in standard cages for three weeks. Pain sensitivity was measured on the tail flick test before and immediately following microinjections of either morphine (0, 2.5, 5.0, 10.0, 20.0 microg/rat) or the more potent morphine metabolite, morphine-6-glucuronide (M6G) (0, 0.03, 0.1, 0.3, 1.0 microg/rat). Baseline tail flick latencies were significantly shorter in active than in inactive rats. Additionally, active animals were less sensitive to the antinociceptive effects of morphine and M6G than inactive rats. These findings provide evidence for the involvement of the CNS in exercise-mediated alterations in pain sensitivity and opiate drug actions.     

Conditioned place aversion produced by microinjections of substance P into the periaqueductal gray of rats

The dorsal periaqueductal gray (DPAG) is one of the main structures involved in the integration of defensive behavior in the brain. In order to investigate the participation of neuropeptides in the generation of aversive states, semicarbazide, a glutamic acid decarboxylase inhibitor, and substance P, an active neuropeptide, were injected into the DPAG and their effects evaluated in the open field and the place conditioning tests. While semicarbazide and substance P both increased locomotor activity only substance P increased grooming in the open field. In the place conditioning procedure similar aversion conditioning was produced by both drugs. These results confirm previous data showing that semicarbazide in the DPAG causes place aversion through reduction of tonic inhibitory mechanisms on neural substrates of aversion. Such mechanisms may include substance P neurons as substance P microinjection into the DPAG also functioned as an unconditioned stimulus in the place aversion test.     

Antinociception following microinjection of dibutyryl cyclic nucleotides into the caudal reticular formation and periaqueductal gray of the rat brain

The tail flick, paw pinch, and hot plate tests were used to assess changes in nociceptive threshold following microinjection of dibutyryl derivatives of cyclic nucleotides into areas of the central nervous system previously shown to be involved in modulation of nociceptive threshold and mediation of morphine analgesia. An elevation in the nociceptive threshold was observed on all three tests following administration of 10 μg dibutyryl cyclic 3':5' adenosine monophosphate (db cAMP) into the caudal brainstem reticular formation (CRF) and periaqueductal gray (PAG). Two μg db cAMP produced the same magnitude of analgesia but had a shorter duration of action. Twenty μg dibutyryl cyclic 3':5' guanosine monophosphate (db cGMP) produced analgesia on all three tests following microinjection at CRF sites but not at PAG sites. These data indicate that morphine analgesia and the antinociception produced by cyclic nucleotides may involve, at least in part, common neuronal substrates. However, the observed capacity of db cAMP to elevate nociceptive threshold does not support the hypothesis that the mechanism of morphine's analgesic action involves inhibition of adenylate cyclase.     

Differential effects of buprenorphine and morphine on immune and neuroendocrine functions following acute administration in the rat mesencephalon periaqueductal gray

The effects of the mu-opioid receptor agonists buprenorphine and morphine on immune and neuroendocrine functions through acute action in the rat mesencephalon periaqueductal gray (PAG) were evaluated. Buprenorphine is an analgesic recently approved for the treatment of drug dependency. In this study, it was shown that injection of an equianalgesic dose of buprenorphine (related to morphine) into the ventral-caudal PAG did not alter splenic NK cell, T cell, and macrophage functions, whereas morphine significantly (p<0.001) suppressed splenic NK cell cytotoxic activity (14-50% reduction), splenic and thymic T cell proliferation to concanavalin A (Con A, 43-76% reduction), antiTCR (T cell receptor) (85% reduction) and IL-2 (36-48% reduction), and macrophage functions including nitric oxide (36-41% reduction) and TNF-alpha production (26%), and phagocytosis of Candida albicans (39%). In addition, buprenorphine was associated with significant (p<0.0001) reductions in adrenocorticotropic hormone (ACTH) and corticosterone (CSO) plasma levels, without altering norepinephrine (NE) and serotonin splenic dialysate levels. In contrast, morphine significantly (p<0.0001) increased glucocorticoid and catecholamine levels in plasma and spleen dialysates, respectively. These results indicated that buprenorphine did not activate either the hypothalamic-pituitary-adrenal (HPA) axis with glucocorticoid release, or the sympathetic nerve (SNS) activity with bioamine production, and was not associated with immunosuppression. The lack of effects of buprenorphine on neuroendocrine systems may be related to its partial agonist properties, the absence of effects on immune system function, and may be associated with the reduction in craving observed in addictive disorders.     

Anxiolytic-like effect of cannabinoids injected into the rat dorsolateral periaqueductal gray

Contradictory results exist concerning the effects of systemic injections of CB(1) cannabinoid receptor agonists on anxiety-related behaviors. Direct drug administration into brain structures related to aversive responses can potentially help to clarify the role of cannabinoids on anxiety. One such structure is the midbrain dorsolateral periaqueductal gray (dlPAG). Therefore, the aim of this study was to test the hypothesis that the activation of the CB(1) receptor in the dlPAG would attenuate anxiety-related behaviors. Male Wistar rats with cannula aimed at the dlPAG received injections of the endogenous cannabinoid anandamide, the anandamide transport inhibitor AM404, the anandamide analogue ACEA or the CB(1) receptor antagonist AM251, and were submitted to the elevated plus maze (EPM), an animal model of anxiety. Anandamide (0.5-50pmol) and ACEA (0.05-5pmol) induced anxiolytic-like effects with bell-shaped dose-response curves, the higher doses being ineffective. The anandamide anxiolytic effect was potentiated by AM404 (50pmol) and prevented by AM251 (100pmol). Neither AM404 (0.5-50pmol) nor AM251 (1-100pmol) alone modified the animal behavior in the EPM. The present study suggests that the dlPAG is a possible neuroanatomical site for anxiolytic-like effects mediated by CB(1) agonists. Furthermore, this work supports the importance of neuronal uptake as a mechanism that limits the in vivo actions of anandamide.     

Anxiolytic-like effects of AP7 injected into the dorsolateral or ventrolateral columns of the periaqueductal gray of rats

RATIONALE: Glutamate antagonists microinjected into the dorsolateral PAG (DLPAG) show an anxiolytic-like profile in the elevated plus maze. Other columns of the PAG are also involved in defensive reactions. Few studies, however, have investigated the effects of pharmacological manipulation of the ventrolateral PAG (VLPAG) on procedures that predict anxiolytic activity. OBJECTIVES: To investigate the effects of the NMDA receptor (NMDAr) antagonist 2-amino-7-phosphonoheptanoic acid (AP7) microinjected into the DL or VLPAG in two procedures that predict anxiolytic activity using distinct aversive contingencies, the elevated plus maze and the Vogel punished licking test. METHODS: Male Wistar rats (7-14/group) with cannulas aimed at the DLPAG or VLPAG received AP7 (2 nmol/0.5 microl) or saline and 10 min later were submitted to the behavioural tests. In the punished licking experiment, water deprived (48 h) animals were allowed to drink for 3 min, receiving a 0.5 mA shock every 20 licks. The elevated plus maze test was performed as described elsewhere. Using this test, a dose response-curve for AP7 (0.2-20 nmol) injected in a smaller volume (0.25 microl) into the VLPAG was also performed. RESULTS: AP7 increased exploration of open arms of the EPM when microinjected into either the DLPAG or VLPAG ( P<0.05, ANOVA). The drug also increased the number of punished licks when administered into those columns (ANOVA, P<0.05). CONCLUSIONS: The results suggest that antagonism of endogenous excitatory amino acid neurotransmission in the DLPAG or VLPAG is able to reverse behavioral suppression induced by distinct aversive contingencies.     

Involvement of endothelin in the pressor response following injection of NMDA to the periaqueductal gray area of rats.

Microinjection of N-methyl-D-aspartate (NMDA) (0.068 to 6.8 nmol) into the periaqueductal gray area (PAG) of anaesthetized rats caused dose-dependent increases in blood pressure. Preinjection (10 min before) of FR 139317 (an ETA receptor selective antagonist; 5 nmol) or SB 209670 (an ETA/ETB receptor non-selective antagonist; 5 nmol) to the PAG reduced the pressor response to NMDA whereas BQ-788 (an ETB receptor selective antagonist; 5 nmol) did not affect the NMDA-induced hypertension. Pretreatment with DL-2-amino-5-phosphono valeric acid (2-APV) (an NMDA receptor selective antagonist, 5 nmol) also abolished the pressor response induced by NMDA. Dose-dependent increases in blood pressure induced by injection of angiotensin II (0.1-10 nmol) to the PAG were unaffected by FR 139317 or SB 209670. Thus, our data indicate that endogenous ET-1, via an action on ETA receptors, contributes to the pressor effects of NMDA within the brain.     

Ionotropic glutamate-receptor antagonists inhibit the aversive effects of nitric oxide donor injected into the dorsolateral periaqueductal gray of rats

Rationale Nitric oxide (NO) is a gas neurotransmitter that may facilitate glutamate release in the central nervous system. NO donors or glutamate agonists injected into the dorsolateral periaqueductal grey (dlPAG) induce flight behaviour.Objectives To test the hypothesis that the defensive reactions induced by an NO donor in the dlPAG would be attenuated by pretreatment with AMPA/kainate or NMDA glutamate receptor antagonists.Methods Male Wistar rats with cannulae aimed at the dlPAG received vehicle, AP7 (a NMDA receptor antagonist, 2 nmol) or NBQX (an AMPA/kainite receptor antagonist, 100 nmol) injection 10 min before the administration of SIN-1 (an NO donor, 300 nmol). Immediately after the last injection, their behavior was observed in an open arena during 10 min.Results SIN-1 induced flight reactions characterized by running and jumps. Pretreatment with AP7 or NBQX completely prevented the effects of SIN-1.Conclusion The results suggest that the aversive reactions induced by an NO donor in the dlPAG depend on ionotropic glutamate receptor activation.     

The effect of L-erythro-dihydroxyphenylserine injected into the lateral ventricle and the hypothalamus on the locomotor activity

The effect of dihydroxyphenylserine (DOPS) on locomotor activity was studied using the Animex activity meter. One microgram of L-erythro-DOPS, a precursor of d-noradrenaline, was injected into the lateral ventricle once a day for one week or into the anterior hypothalamic area (AHA) once. After the intraventricular injection, the total locomotor activity (from 8:00 p.m. to 8:00 a.m.) of the rats injected with DOPS was significantly less than that of the rats injected with an artificial cerebrospinal fluid (5-ion). Analysis of the locomotor activity in consecutive 2-hr periods showed that the activity of the DOPS group during the time intervals of 10 p.m.-12 a.m., 12 a.m.-2 a.m. and 2 a.m.-4 a.m. was significantly less than that of the control group. After injection of DOPS or 5-ion into AHA, the total activity of the DOPS group was significantly less than that of the control. Analysis of the activity of the DOPS group for each 2-hr period between 10 p.m.-4 a.m. was also significantly less than that of the control. On the basis of these findings, the effect of DOPS in the brain noradrenergic system are discussed.     

Evaluation of THIP in standard tests for analgesic activity: Occurrence of antinociception and hyperalgesia

THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol), a structurally rigid analog of the GABA-agonist muscimol, was investigated for antinociceptive activity in a variety of preclinical tests for analgesic activity. Antinociceptive activity was observed in the mouse writhing, mouse hot plate, rat tail flick, rat inflamed paw, and monkey shock titration tests. In the mouse writhing, mouse hot plate, and rat tail jerk experiments, periods of significant hyperalgesia were noted either prior to or following the occurrence of THIP-induced antinociception. At those times when an antinociceptive effect of THIP could be demonstrated in the test systems employed in this study, a variety of unfavorable effects were noted including sedation, ataxia, myoclonic jerks, and vomiting. These side-effects of THIP first appeared near the dose that produced antinociception in 50% of the animals (ED₅₀ value) and became progressively more intense as the dose increased. Neither the narcotic antagonist naloxone, the cholinergic antagonist atropine, nor the GABA-antagonists bicuculline or picrotoxin blocked the antinociceptive activity of THIP. The synthesis of prostaglandins was not inhibited by THIP. The antinociceptive activity of THIP is an interesting lead in the search for a novel analgesic that lacks the undesirable effects of opiates. However, the occurrence of hyperalgesia and marked side-effects at doses near the effective analgesic dose may limit THIP's therapeutic potential.     

Analgesic tolerance to microinjection of the micro-opioid agonist DAMGO into the ventrolateral periaqueductal gray

Repeated administration of the relatively low-efficacy μ-opioid receptor agonist morphine induces tolerance to its antinociceptive effects. High-efficacy agonists such as D-Ala2NMePhe4,Gly-ol5 (DAMGO) have been shown to be less effective at producing tolerance, suggesting that different neural mechanisms underlie tolerance to these agonists. However, the correlation between agonist efficacy and tolerance development has not been examined within the ventrolateral periaqueductal gray (vPAG), a brain area known to be crucial for the development of morphine tolerance. The current studies examined whether tolerance to DAMGO occurs within the vPAG, and whether repeated treatment with DAMGO into the vPAG alters the development of morphine tolerance. The results showed that repeated vPAG microinjections of DAMGO induced robust tolerance and cross-tolerance to morphine. Further, co-administration of a low dose of DAMGO with morphine potentiated morphine tolerance. These findings indicate that similar mechanisms underlie tolerance to morphine and DAMGO within the vPAG.     

Involvement of 5HT1A receptors in the anxiolytic-like effects of cannabidiol injected into the dorsolateral periaqueductal gray of rats

RATIONALE: Cannabidiol (CBD) is a non-psychotomimetic constituent of Cannabis sativa plant that induces anxiolytic effects. However, the brain sites and mechanisms of these effects remain poorly understood. The dorsolateral periaqueductal gray (dlPAG) is a midbrain structure related to anxiety that contains receptors proposed to interact with CBD such as 5HT1A. In addition, since CBD has been shown to inhibit anandamide metabolism, CB1 receptors could also be involved in the effects of this cannabinoid. OBJECTIVES: To investigate if the dlPAG could be a possible site of the anxiolytic effects induced by CBD and if these effects depend on CB1 or 5HT1A receptors. MATERIALS AND METHODS: Male Wistar rats with cannulae aimed at the dlPAG were tested in the elevated plus maze (EPM) and the Vogel conflict test (VCT). RESULTS: CBD injected into the dlPAG produced anxiolytic-like effects in the EPM with a bell-shaped dose-response curve. The anxiolytic effect of CBD was confirmed in the VCT. These effects were prevented by WAY100635, a 5HT1A receptor antagonist, but not by AM251, an antagonist of CB1 receptors. CONCLUSION: These results suggest the CBD interacts with 5HT1A receptors to produce anxiolytic effects in the dlPAG.     

A comparison of the antinociceptive responses to the GABA-receptor agonists THIP and baclofen

The antinociceptive action of the gamma-aminobutyric acid (GABA) agonists THIP and baclofen was evaluated in mice using hot-plate (48 and 55 degrees C) and tail-immersion (50 degrees C) procedures. It was found that atropine reversed antinociception induced by THIP but not that induced by baclofen in the 48 degrees C test, whereas the anticholinergic drug blocked the response to both GABA agonists when the stimulus was provided by a 55 degrees C hot-plate. Atropine methylnitrate, mecamylamine, picrotoxin and bicuculline had no effect on antinociception induced by THIP or baclofen. Prior treatment with haloperidol enhanced only the response to baclofen on the 55 degrees C hot-plate. A reciprocal cross-tolerance was found between THIP and baclofen in the tail-immersion assay, although only THIP exhibited cross-tolerance to morphine. These results suggest that while the analgesic response to THIP and baclofen is partially mediated by a common system, the two agents act by independent mechanisms as well.     

Involvement of local orphanin FQ in the tolerance induced by repeated microinjections of morphine into ventrolateral periaqueductal gray in rats

The present study evaluated the role of ventrolateral periaqueductal gray (vlPAG)-located orphanin-FQ (OFQ) in the opioid tolerance induced by repeated microinjections of morphine (MOR) into vlPAG. Microinjection of MOR (5 microg/0.5 microl) into vlPAG caused antinociception as quantified with the tail flick and the hot plate tests. When MOR microinjection was repeated twice daily, the antinociceptive effect disappeared within 2 days (tolerance). However, if MOR microinjection was preceded by the OFQ receptor antagonist nocistatin (NST; 1 ng/0.5 microl), the microinjections of MOR did not induce tolerance. If NST microinjections were suspended, subsequent MOR microinjections induced tolerance. In MOR-tolerant rats, a single NST microinjection into vlPAG was enough to restore the antinociceptive effect of MOR. Furthermore, if OFQ (1 ng/0.5 microl) was microinjected into vlPAG, then a MOR microinjection administered 15 min later into vlPAG did not elicit antinociception. Finally, opioid tolerance induced by repeated systemic MOR injections (5 mg/kg, i.p.) was reversed by a single microinjection of NST into vlPAG. This emphasizes the central importance of vlPAG-located OFQ in the MOR tolerance.     

Antinociceptive activitiy of narcotic agonist and partial agonist analgesics and other agents in the tail-immersion test in mice and rats.

The antinociceptive activity of a series of narcotic agonist (morphine-like) and partial agonist (pentazocine-like) agents was assessed in both mice and rats using a tail-immersion nociceptive test. Narcotic agonist agents (diamorphine, etorphine, morphine and pethidine) displayed characteristically steep and parallel log dose-response lines in both species, whether administered peripherally or centrally. The partial agonists examined (cyclazocine, nalorphine and pentazocine) also produced parallel but much shallower log dose-response lines of essentially different slope to the agonists. The claimed pure antagonist naloxone also exhibited low-order antinociceptive activity, with a dose-response line parallel to that of the partial agonists. The tail-immersion test in mice showed specific sensitivity to narcotic agonists and partial agonists, while peripherally acting analgesics (e.g. aspirin, indomethacin, paracetamol and sodium salicylate) were generally inactive. It is therefore suggested that this test would be of particular value in assessing antinociceptive activity of the partial agonist type in small laboratory animals.     

Alterations in the effects of dopamine agonists and antagonists on general activity in rats following chronic morphine treatment

Results of two experiments revealed that morphine produced both time-and dose-dependent effects on the general activity of rats following a single acute administration, depression being observed 30 min after the injection and hyperactivity at 150 min. Tolerance to the depressive effects of morphine was observed within 7 days of chronic, once daily treatments, the depression being replaced by a hyperactivity that included a high degree of self-directed oral stereotyped behaviour. Dose-response analyses of the effects of d-amphetamine, an indirectly acting dopamine agonist, and apomorphine, a directly acting dopamine agonist, revealed a shift in the dose-response curves following chronic morphine treatment, indicating that the animals were supersensitive to these agents. Conversely, the dose-response curve for pimozide, a directly acting dopamine antagonist, was shifted in a direction indicating that the animals were subsensitive to this agent. The dose-response curve for haloperidol, another dopamine antagonist, was unchanged. These findings are consistent with the hypothesis that an increase in the number of dopamine receptors may develop during chronic treatment with morphine.     

Passage into the rat brain of dopa and dopamine injected into the lateral ventricle

1. The green fluorescence of catechols of the brain was studied in rats after intraventricular injection of L-dopa or dopamine in untreated rats as well as in rats in which dopa decarboxylase (DC) was inhibited by Ro 4602, or the monoamine oxidase by nialamide.2. From the patterns of fluorescence obtained in these conditions, it is concluded that in the areas close to the liquor space dopa is rapidly taken up by the endothelium of the brain capillaries and then converted into dopamine; when the DC is inhibited the dopa passes freely from the endothelium into the brain tissue.3. On the other hand, dopamine passes from the liquor space via the ependyma directly into the brain tissue and from there into the capillary endothelium which is thus permeable to the amine in the direction from the brain tissue, in contrast to the impermeability in the direction from the capillary lumen.     

Spontaneous unit activity in the globus pallidus following cumulative injections of morphine in phenobarbital- or chloral hydrate-anesthetized rats

The effect of systemically administered morphine on spontaneous unit activity, recorded from the globus pallidus, was evaluated in this study. A wide range of doses of morphine was administered in order to characterize the influences of morphine on pallidal activity in a dose-related manner. Two separate studies were conducted. In the first study, a semichronic preparation, lightly anesthetized with phenobarbitol, was used. Acutely prepared, chloral hydrate-anesthetized rats were utilized in the second experiment.With phenobarbital, morphine caused a significant reduction in pallidal activity in 75% of the cells recorded, whereas only 45% of the pallidal cells responded similarly to injection of morphine in chloral hydrate-anesthetized animals. However, the dose of morphine required to decrease unit activity was substantially less with chloral hydrate than with phenobarbital anesthesia.