Prostaglandin E2, cyclic adenosine monophosphate and morphine analgesia.

Intravenous administration of prostaglandin E2 (PGE2) to mice results in a significant distribution of PGE2 into the brain and an elevation of cyclic adenosine monophosphate (cAMP) in the midhindbrain and corpus striatum. Neither acute morphine administration nor morphine tolerance alters this response. Morphine alone also elevates cAMP levels. Although these elevations are blocked by the narcotic antagonist, naloxone, they only occur at supra-analgesic doses. Therefore morphine analgesia does not correlate with either elevation of cAMP levels of antagonism of PGE2-induced elevations of cAMP.     

The effect of capsaicin on the adenylate cyclase activity of rat brain.

The effect of capsaicin on the adenylate cyclase activity in different regions of the rat brain (preoptic area of the hypothalamus, cerebral cortex and cerebellum) was investigated. Capsaicin added in vitro (10(-7)-10(-5) M) increased the adenylate cyclase activity of different brain regions. Following systemic capsaicin desensitization adenylate cyclase activity was significantly increased in the preoptic area. The enhanced adenylate cyclase activity in the preoptic area was inhibited by the vitro addition of capsaicin or 5-HT, whereas desensitization did not affect the in vitro activating effect of capsaicin in other brain regions (cerebral cortex, cerebellum). It is assumed that the pharmacological effect of capsaicin in the preoptic area is mediated through the activation of adenylate cyclase. Since capsaicin induces irreversible impairment of the function of warmsensitive hypothalamic neurons it is assumed that adenylate cyclase is involved in maintaining normal thermoregulatory functions.     

Differential effect of mu, delta, and kappa opioid agonists on adenylate cyclase activity

D-Ala2, D-Leu5-enkephalin (DADLE) and dynorphin1-13 (Dyn1-13) inhibited striatal adenylate cyclase activity, both basal and dopamine-stimulated (DA), in rats and guinea pigs. The kappa-agonists bremazocine (BRZ), U-50,488 (trans-3,4-dicloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]- benzeneacetamide), and U-69,593 (5 alpha, 7 alpha 8 beta)-(-)-N-methyl-N-(7-(1-pyrrolidinyl-1-oxaspiro (4.5)dec-8yl) benzeneacetamide inhibited only the basal adenylate cyclase activity, and such an effect was restricted to guinea pig striatum, an area known to contain a high density of kappa-binding sites. Moreover, BRZ was found to antagonize the inhibitory effect of both DADLE and Dyn1-13 in rat striatum.     

Dissociation of the aggregating effect and the inhibitory effect upon cyclic adenosine monophosphate accumulation by adrenaline and adenosine diphosphate in human platelets

Recent evidence indicates that adrenaline and adenosine diphosphate each have separate stimulus-response pathways for induction of aggregation and inhibition of cAMP accumulation. We have used a natural model to test the validity of this evidence, i.e. patients from two kindreds with an inherited bleeding disorder due to absent aggregation to adrenaline and no secondary wave response to large concentrations of adenosine diphosphate. Our studies showed that the inhibitory effect of adrenaline and adenosine diphosphate on PGE1-induced increase of cAMP in the patients was not different from that of the controls both for adrenaline and adenosine diphosphate. These results therefore support the present evidence that both adrenaline and adenosine diphosphate apply separate pathways in these two platelet functions.     

Chronic but not acute intracerebroventricular administration of amyloid beta-peptide(25-35) decreases somatostatin content, adenylate cyclase activity, somatostatin-induced inhibition of adenylate cyclase activity, and adenylate cyclase I levels in the rat hippocampus

Although alterations in adenylate cyclase (AC) activity and somatostatin (SRIF) receptor density have been reported in Alzheimer's disease, the effects of amyloid beta-peptide (Abeta) on these parameters in the hippocampus are unknown. Our aim was to investigate whether the peptide fragment Abeta(25-35) can affect the somatostatinergic system in the rat hippocampus. Hence, Abeta(25-35) was injected intracerebroventricularly (i.c.v.) to Wistar rats in a single dose or infused via an osmotic minipump connected to a cannula implanted in the right lateral ventricle during 14 days. The animals were decapitated 7 or 14 days after the single injection and 14 days after chronic infusion of the peptide. Chronic i.c.v. infusion of Abeta(25-35) decreased SRIF-like immunoreactive content without modifying the SRIF receptor density, SRIF receptor expression, or the Gialpha(1), Gialpha(2), and Gialpha(3) protein levels in the hippocampus. This treatment, however, caused a decrease in basal and forskolin-stimulated AC activity as well as in the capacity of SRIF to inhibit AC activity. Furthermore, the protein levels of the neural-specific AC type I were significantly decreased in the hippocampus of the treated rats, whereas an increase in the levels of AC V/VI was found, with no alterations in type VIII AC. A single i.c.v. dose of Abeta(25-35) exerted no effect on SRIF content or SRIF receptors but induced a slight decrease in forskolin-stimulated AC activity and its inhibition by SRIF. Because chronic Abeta(25-35) infusion impairs learning and memory whereas SRIF facilitates these functions, the alterations described here might be physiologically important given the decreased cognitive behavior previously reported in Abeta-treated rats.     

Interactions of antiepileptic drugs on adenylate cyclase and phosphodiesterases in rat and mouse cerebrum.

Five anticonvulsant agents were tested in broken cellular preparations of mouse and rat cerebral cortex for their ability to modify either adenylate cyclase or three forms of cyclic AMP-dependent phosphodiesterase. In both species only carbamazepine inhibited the stimulation of cortical adenylate cyclase by catecholamines (norepinephrine and/or dopamine). Two benzodiazepines, diazepam and clonazepam, enhanced basal and catecholamine-stimulated adenylate cyclase. The latter observations were expecially prominent when phosphodiesterase inhibitors were removed from the preparations. In all instances diazepam was more potent than clonazepam and additionally exerted a more pronounced blockade of high and low K_m phosphodiesterase (mouse cerebrum) and the Ca²⁺-dependent, heatstable, activated phosphodiesterase in the rat cortex. Of the other anticonvulsants evaluated (carbamazepine, phenytoin, and phenobarbital), only phenobarbital inhibited phosphodiesterase, i.e., the low K_m form.     

The mechanisms of action of lithium. II. Effects on adenylate cyclase activity and beta-adrenergic receptor binding in normal subjects.

As part of a study of the effects of lithium carbonate on neurochemical function in man, platelet and lymphocyte adenylate cyclase activity and lymphocyte beta-adrenergic receptor binding characteristics were determined before and after 2 weeks of lithium treatment in 10 normal volunteers. Lithium had differential effects on platelet and lymphocyte adenylate cyclase activity. In platelets, basal and stimulated (guanyl imidodiphosphate [Gpp[NH]p] or cesium fluoride) adenylate cyclase activity was significantly augmented by lithium treatment. By contrast, in lymphocytes, Gpp(NH)p- and cesium fluoride-stimulated adenylate cyclase activity was unaffected, while basal activity was decreased modestly after lithium. These results are consistent with preclinical studies that suggest that lithium's effects on adenylate cyclase activity are specific with respect to tissue and brain region and that lithium may interfere with guanine nucleotide binding (G) protein function. Lithium treatment significantly increased the ratio of low- to high-affinity dissociation constants for agonist displacement of antagonist binding to lymphocyte beta-adrenergic receptors (thought to reflect coupling between the beta-adrenergic receptor and stimulatory G protein). Lithium had significant effects on measures associated with signal transduction that might be contrasted to its more subtle effects on neuronal function (norepinephrine release) and neuroendocrine systems (responses to serotoninergic challenge) in these same subjects (reported in a companion article). Lithium's primary site of action may be on signal transduction mechanisms. These effects subsequently may be manifested in changes in neurotransmitter function that may be important to lithium's mood-stabilizing actions.     

Reduction of the microglial cell number in rat primary glial cell cultures by exogenous addition of dibutyryl cyclic adenosine monophosphate

The present work examined the effects induced by dibutyryl cyclic adenosine monophosphate (dB–cAMP) on microglial cells in primary glial cell cultures from newborn rats. Microglial cells were identified by OX42 immunohistochemistry and nucleoside diphosphatase histochemistry. Double staining for astrocytes was carried out by combination with glial fibrillary acidic protein immunolabeling. Addition of 0.25 mM dB–cAMP to the cultures decreased the microglial cell number about sixfold. The findings suggest that the effect of dB–cAMP on the microglial cells might be either a direct action of dB–cAMP on the microglial cells or an indirect effect mediated by the astroglial cells.     

Interaction of neuropeptides and biogenic amines on cyclic adenosine monophosphate accumulation in hypothalamic nuclei

Neuropeptides and biogenic amines known to be present in neurons or afferent terminals in the paraventricular nucleus (PVH), supraoptic nucleus (SON) and/or lateral hypothalamus (LH) were added to small areas of these structures obtained by micropuncture and cyclic adenosine monophosphate (cAMP) levels were measured. cAMP accumulation occurred in PVH, SON and LH in response to neuropeptides of the secretin family, such as vasoactive intestinal peptide (VIP) and in response to catecholamines. Bradykinin, alpha-melanocyte-stimulating (alpha-MSH), luteinizing hormone-releasing hormone (LH-RH), oxytocin and carbamylcholine stimulated cAMP accumulation selectively in one or two of the above structures. Glucagon, cholecystokinin (CCK), somatostatin (SRIF), corticotropin-releasing factor (CRF), thyrotropin-releasing hormone (TRH), adrenocorticotropin (ACTH), melanocyte-stimulating hormone (MSH), methionine enkephalin (Met-Enk), beta-endorphin, neurotensin, bombesin and angiotensin II did not effect cAMP levels while leucine enkephalin (Leu-Enk), arginine vasopressin and gamma-aminobutyric acid (GABA) elicited regionally selective decreases in basal levels of cAMP. When interactions between some of these compounds were measured, VIP and norepinephrine exerted a more than additive effect on cAMP elevation in the PVH, while the effect on cAMP of the SON and LH was additive.     

Differential effect of lithium on fos protooncogene expression mediated by receptor and postreceptor activators of protein kinase C and cyclic adenosine monophosphate: model for its antimanic action.

Lithium salts are the most effective agents used in treating manic-depressive illness. It has been suggested that lithium's therapeutic efficacy could be due to an inhibitory effect on either inositol phospholipid (IP) and/or cyclic nucleotide metabolism. We have investigated the effect of lithium on these two signal transduction pathways in PC12 pheochromocytoma cells by studying a common effector target, expression of the fos protooncogene. We find that lithium, at therapeutic doses, has an augmenting effect on phosphatidylinositol (PI)-mediated fos expression induced by activating a muscarinic cholinergic pathway, whereas it has no effect, at tenfold the therapeutic dose, on fos expression induced by receptor or postreceptor activators of cyclic adenosine monophosphate (cAMP). The lithium augmenting effect is also observed when the cells are treated with phorbol esters, which directly activate protein kinase C (PKC), suggesting that the level of lithium's interaction with the IP pathway is at the postreceptor level. We also show that phorbol esters induce extensive down regulation of subsequent cholinergic and phorbol ester responsiveness as well as heterologous down regulation of cAMP responses. Treatment of down-regulated cells with lithium leads to an enhanced responsiveness when cells are rechallenged with agonists that activate PKC but not by agonists that stimulate cAMP. We also show that carbamazepine, another antimanic agent, has an inhibitory effect on cAMP-mediated fos but no effect on the IP pathway. The opposite effects of lithium and carbamazepine on two critical transducing systems suggest a model for the antimanic action of these agents.     

Postnatal development of striatal dopamine function. II. Effects of neonatal 6-hydroxydopamine treatments on D1 and D2 receptors, adenylate cyclase activity and presynaptic dopamine function

To evaluate the influence of patch and matrix ingrowth of DA terminals upon striatal DA (dopamine) receptor function, we performed bilateral intrastriatal (i.s.) or single intracisternal (i.c.) injections of 6-hydroxydopamine (6-OHDA) into rat pups at various postnatal ages and determined D1 and D2 receptor binding, adenylate cyclase activities and markers for presynaptic DA terminal density and turnover as the animals matured. All injection schedules yielded: (a) variable and partial loss of DA, (b) increased DA turnover, (c) small (15-40%) increases in D1 receptor number but no change in affinity for antagonist ([3H]SCH 23390), (d) 2-3-fold increases in affinity of D1 receptors for agonist (SKF 38393) with preserved regulation of agonist affinity by guanine nucleotide, (e) no significant changes in DA-, guanine-nucleotide-, manganese- and forskolin-stimulated AC (adenylate cyclase) activity. D2 receptor binding was evaluated between 1 and 7 weeks of age in animals with i.s. treatment and 7 and 10 weeks of age in animals with i.c. treatment and was reduced by 40-50% with both treatment regimens. [3H]mazindol binding, a marker for presynaptic terminal DA transport sites, was reduced 30-40% by multiple i.s. or i.c. treatment regimens. In animals treated with one i.s. injection, [3H]mazindol binding was reduced 70% at 1 week of age, equal to control by 2 weeks and 14-46% greater than control between 3 and 7 weeks. We conclude that striatal D1 receptor sites maintain their density and second messenger function independently of postsynaptic DA terminal ingrowth, whereas the development of D2 receptor sites is sensitive to disruptions of DA terminal ingrowth.     

行为缺损抑郁大鼠脑环磷酸腺苷含量及蛋白激酶C表达的变化

目的　在第二信使水平研究抑郁症发病的生化机制及抗抑郁药帕罗西汀的药理作用机理。方法　 15只Sprague Dawley雄性大鼠随机分为抑郁模型组 5只 ,帕罗西汀治疗组 5只 ,正常对照组 5只。采用行为限制方法建立应激诱导行为缺损抑郁模型 ,连续 7日将所有动物绑缚在特制的观察笼中 ,第 7天行为限制 2 4h后对各组大鼠进行旷场试验 ;旷场试验后帕罗西汀组每天腹腔注射盐酸帕罗西汀 (3mg·kg-1·d-1) 1次 ,模型组、对照组每天腹腔注射等体积生理盐水 1次 ,均持续 14天。用放射免疫分析方法测定大鼠脑皮层环磷酸腺苷 (cAMP)的含量 ,用蛋白质免疫印渍法检测脑皮层蛋白激酶CβⅡ (PKCβⅡ )的表达水平。结果　抑郁大鼠脑皮层cAMP含量 (0 0 14± 0 0 0 1)pmol/mg ,低于正常对照组 (0 10 3± 0 0 6 4 )pmol/mg ,P <0 0 5 ;PKCβⅡ蛋白表达 (7± 4 ) % ,较对照组 (2 2± 4 ) %减弱 ,P <0 0 1。用帕罗西汀治疗 2周后 ,帕罗西汀治疗组大鼠脑皮层cAMP含量较治疗前无明显变化 (P >0 0 5 ) ,但PKCβⅡ蛋白表达则明显增强 [(34± 5 ) % ],与接受生理盐水腹腔注射的抑郁模型组大鼠[(7± 4 ) % ]的差异有非常显著性 (P <0 0 1)。结论　抑郁发生可能与第二信使腺苷酸环化酶 环磷酸腺苷 (AC cAMP)、磷酸肌醇 钙离子     

Axonal transport of adenylate cyclase activity in normal and axotomized frog sciatic nerve

Adenylate cyclase activity accumulated proximal to a constriction placed around the frog sciatic nerve. The rate of accumulation was linear between 8 and 24 h following placement of the constriction; accumulation rate declined substantially after 24 h. Accumulation of activity distal to the constriction in normal nerve was not significantly different from control for the first 72 h, but increased at 5 days. These data are interpreted as indicating that adenylate cyclase is transported from the cell body to the nerve terminals in normal frog nerve, but not in the reverse direction. Following axon transection, anterograde transport of adenylate cyclase activity declined, but a transient retrograde transport of adenylate cyclase activity appeared. In addition, adenylate cyclase activity accumulated in the proximal transected nerve stump during the period when Schwann cell proliferation and the initiation of nerve regeneration both appear. The pattern of response of adenylate cyclase activity to nerve injury suggests that the adenylate cyclase: cAMP system could play some role in peripheral nerve regeneration.     

Localization of cyclic adenosine monophosphate in the teleost retina: effects of dopamine and prolonged darkness

Localization of cyclic adenosine monophosphate (cAMP) in the white perch retina was carried out with immunohistochemical and autoradiographic methods. Following exposure to dopamine or prolonged darkness, cAMP staining was observed by immunohistochemistry in the distal part of the inner nuclear layer, i.e. in the horizontal cells. After exposure to dopamine, increased levels of cAMP were also observed by autoradiography in many horizontal cells. Finally, increased levels of cAMP staining were observed immunohistochemically following incubation with dopamine in all types of cone-related horizontal cells that had been isolated and maintained in culture.