摘要:

AbstractWe stably expressed a rat D3 receptor cDNA in C6glioma cells (C6‐D3 cells), quantifying receptor expression with the radioligands [125I]epidepride (KD= 0.1 nM) and [3H]spiperone (KD= 0.7 nM). As reported previously for D2 receptors, quinpirole induced a 9–16% increase in the rate of extracellular acidification by C6‐D3 cells. The acidification was inhibited by epidepride and by the Na+/H+antiporter inhibitors, amiloride and methylisobutylamiloride, but pertussis toxin treatment had no effect on quinpirole‐induced extracellular acidification. These data suggest that D3 receptor stimulation of Na+/H+exchange in C6glioma cells is not mediated by the pertussis toxinsensitive G proteins, Gior Go. Overnight treatment of C6‐D3 cells with N‐propylnorapomorphine, dopamine, or quinpirole resulted in large concentration‐dependent increases (up to 500%) in the density of D3 receptors on membranes prepared from the cells. Antagonists had smaller, variable effects on the density of D3 receptors in C6‐D3 cells, except for domperidone, which significantly increased the density of D3 receptors. Treatment with pertussis toxin had no effect on the agonist‐induced receptor up‐regulation, indicating that an interaction with pertussis toxin‐sensitive G proteins was not required. Densitometry analysis of Northern blots of RNA prepared from C6‐D3 cells showed no significant N‐propylnorapomorphine‐induced increase in D3 receptor message. Treatment with cycloheximide, however, completely prevented receptor up‐regulation by N‐propylnorapomorphine. Pretreatment of C6‐D2 cells with 1'0 pM DA resulted in a substantial heterologous sensitization, in which isoproterenol‐stimulated adenylyl cyclase activity was enhanced more than twofold. In contrast, isoproterenol‐stimulated enzyme activity was inhibited by greater than 50% in C6‐D3 cells pretreated with dopamine. These results confirm one functional response to activation of D3 receptors and demonstrate that the density of D3 receptors, like D2 receptors, is increased after incubation of intact cells with agonists. © 1995 Wiley‐Liss, Inc.This article is a US Government work and as such, is in the pub

ISSN:0887-4476    

DOI:10.1002/syn.890210102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe earliest treatments of anxiety included cathartics and emetics, which were used to remove the excess of black bile (hence our word melancholia) thought to be responsible for the patient's demeanor. By the 1700s, physicians were prescribing drugs that are more selective for the CNS, chiefly opium and strengthening tonics. In the 1860s cardioactive drugs such as atropine, aconite, and digitalis were assumed to counteract anxiety because it could be associated with tachycardia andlor melancholia. A little later, the emergence of laboratory animal models, culminating in the conditioned avoidance response, and also Freudian psychiatry, permitted the evolution of new definitions of anxiety, as well as the introduction of sedative agents such as KBr, chloral hydrate, and barbiturates for its treatment. The first somewhat selective anxiolytics, reserpine, meprobamate, and chlorpromazine, appe ared in the early 1950s, while in 1959 the benzodiazepines were the first to prove more selective than all the others in a systematic battery of screening tests. © 1995 Wiley‐Liss, I

ISSN:0887-4476    

DOI:10.1002/syn.890210103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTo investigate the use of α‐[3H]methyl tryptophan (α‐[3H]MTrp) as a tracer for the in vivo study of brain serotonergic neurons, we examined whether α‐[3H]MTrp and its metabolite α‐[3H]methyl serotonin (α‐[3H]M5‐HT) selectively label serotonergic neurons and whether once accumulated in these neurons, the radioactive metabolite behaves like endogenous serotonin. Rats received a systemic injection of 1–5 mCi of α‐[3H]MTrp and 24 h later their brains were immediately removed or fixed by perfusion before removal. Tissue sections in which serotonergic neurons had been immunostained for 5‐HT or its synthesizing enzyme, tryptophan hydroxylase, were processed for radioautography at the light and electron microscopic level. In another group of rats, the release of radioactivity from different brain areas was studied both under basal and depolarizing conditions. In the dorsal raphe nucleus, the light microscopic examination revealed almost complete colocalization between serotonergic neurons and those that accumulated radioactivity, with a heterogeneity in the content of α‐[3H]M5‐HT among the various cells. At the ultrastructural level, immunoidentified serotonergic perikarya and dendritic processes in the dorsal raphe nucleus, as well as nerve terminals in the cerebral cortex were also found to contain α‐[3H]M5‐HT. Under basal conditions, radioactivity was released from the brainstem raphe region and from projection areas such as the striatum and hippocampus. The basal output of α‐[3H]M5‐HT increased approximately twofold after a depolarizing 50 mM KCl solution was added to the perfusion fluid. These findings suggest that newly synthesized α‐[3H]M5‐HT can be released both at somatodendritic and terminal sites. In sum, the present results demonstrate the selectivity of α‐[3H]MTrp as a tracer for serotonergic cells, and further suggest that α‐[3H]MTrp radiolabelling provides for a direct assessment of the in vivo dynamics of brain serotonergic neur

ISSN:0887-4476    

DOI:10.1002/syn.890210104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe long‐term effects of a unique injection of reserpine (5 mg/kg s.c.) on the vesicular monoamine transporter and dopamine uptake complex have been investigated, in parallel with behavioral and neurochemical effects. Early after treatment, a dramatic decrease in locomotor activity, as well as a marked depletion in striatal dopamine (DA), associated with a prominent enhancement in dopaminergic turnover were observed in reserpine‐treated rats. From 2 to 60 days after reserpine injection, a recovery in locomotor activity occurred, in parallel with an increased DA content in the striatum, reaching about 50% of controls at day 60. At this time, the dopamine turnover was quite normal. The density of the dopamine uptake sites in the striatum, studied with3H GBR12783, was unchanged after reserpine treatment at any time studied up to 60 days. By contrast, the density of binding sites for3H dihydrotetrabenazine (3H TBZOH), a marker for the vesicular monoamine transporter, remained dramatically decreased in the striatum all over the time of the study (>−90% of controls at day 2 and −80% at day 30 and 60). A lesser decrease (−60%) was observed in the substantia nigra pars compacta (SNc), 2 and 30 days after reserpine treatment. This suggests that at least 60% of the vesicular monoamine transporter is sensitive to reserpine in this cell bodies region, indicating that this proportion of the transporter is integrated in functional vesicles, a prerequisite for reserpine binding. On the other hand, in spite of profound modifications of DA levels and neuronal activity, induced by a persistent blockade of the vesicular uptake process, the density of mRNA encoding the vesicular monoamine transporter remained constant in the SNc from 2 to 60 days following reserpine injection. © 1995 Wiley

ISSN:0887-4476    

DOI:10.1002/syn.890210105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe present study was designed to characterize the pharmacological profile of dopamine D1‐like receptors in the rat cerebellar cortex and to assess if these receptor sites undergo age‐related changes. Cerebella of young (3 months), adult (12 months), and old (27 months) male Wistar rats were examined by using radioligand binding techniques and light microscope autoradiography. The non‐selective dopamine D1‐like radioligand [3H]SCH 23390 was specifically bound to sections of rat cerebellum. The findings that dopamine displaced [3H]SCH 23390 binding in the submicromolar range suggest the labelling of a dopamine D5(or D1B) receptor subtype. The affinity of [3H]SCH 23390 for dopamine D1‐like receptors was similar in the cerebellar cortex of the three animal groups investigated, whereas radioligand binding techniques revealed a gradual age‐related reduction of the density of binding sites. Light microscope autoradiography showed the localization of [3H]SCH 23390 binding sites primarily in the molecular layer and to a lesser extent in the Purkinje neuron layer of the cerebellar cortex. Aging was accompanied by a loss of [3H]SCH 23390 binding sites affecting mainly the molecular layer. The age‐dependent loss of dopamine D1‐like receptors is more pronounced if detected with radioligand binding techniques than with light microscope autoradiography. This suggests that the decrease of dopamine D1‐like receptors observed in aging rat cerebellar cortex may depend in part on changes in the receptor expression and in part on cortico‐cerebellar structural changes. ©

ISSN:0887-4476    

DOI:10.1002/syn.890210106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA positron emission tomograph (PET) was used to image D2dopamine receptor function in rat striata and to obtain regional time‐radioactivity curves from individual rat brains following i.v. injection of carbon‐11‐labelled raclopride. Despite the limited resolution of the camera, together with associated spillover and partial volume effects, the kinetic data obtained from striata were such that specific binding of the radioligand could be quantified unilaterally, using a reference tissue compartmental model, with cerebellum data as an indirect input function. With the exception that the rat is anaesthetised, the experimental system is analogous to the acquisition and collection of clinical PET data and, by using animal models of disease, can be used to aid the interpretation of clinical studies. Using 6‐hydroxydopamine (6‐OHDA) lesioning of the substantia nigra pars compacta to produce a rat hemiparkinsonian model, the present results confirm that deafferentation causes a supersensitivity of post‐synaptic D, dopamine receptors. Saturation studies indicated that the measured 23% increase in [11C]raclopride binding potential reflected a change in receptor affinity. Modulation of extracellular dopamine concentration, monitored by in vivo microdialysis, demonstrated that the increased binding was unlikely to be due to a reduction in receptor occupancy by endogenous dopamine. Acute administration of L‐3, 4‐dihydroxyphenylalanine (L‐dopa) also caused an increase in [11C]raclopride binding potential, confirming the suggestion that L‐dopa plays a more complex role than that of dopamine precursor in the nigrostriatal pathway. ©

ISSN:0887-4476    

DOI:10.1002/syn.890210107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThis study examined the normal development of neuronal activity in the suprachiasmatic nuclei (SCN) of rats between age 3–60 days, using Fos protein‐like immunoreactivity (Fos‐LI) as a marker. At age 3 days, Fos‐positive nuclei are sparsely distributed throughout the SCN. Between age 3–10 days, the density of labeled nuclei increases significantly. Fos‐LI labeling is maximal at 10 days. Between age 10–14 days, the number of labeled nuclei decreases and remains relatively constant thereafter, although the intensity of the reaction product diminishes as the animal matures. By age 60 days, the number of Fos‐LI labeled nuclei in the SCN is substantially decreased and is essentially the same as in the 3‐day‐old rat. The appearance of Fos‐LI nuclei in the SCN during development appears to reflect the development of visual system afferents to the nucleus as well as the development of intrinsic SCN synaptology.

ISSN:0887-4476    

DOI:10.1002/syn.890210108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractOpiate receptors play major roles in analgesic and euphoric effects of opiate drugs. Recent cloning of cDNAs encoding the rodent and human μ receptor revealed high homology between the predicted receptors but also some sequence differ‐ ences. To determine if these sequence differences produced significant changes in ligand‐selectivity profiles, we assessed these profiles in expressing COS and CHO cell lines using the agonist ligand [125I]IOXY‐AG0 (6β‐[125Iodo]‐3,14‐dihydroxy‐17‐methyl‐4,5α‐epoxymorphinan). This ligand's high specific activity (2, 200 Ci/mmol) and high affinity for μ opioid receptors generated high signal‐to‐noise ratio binding. The resulting ligand‐ selectivity profiles of the human and rat mu; receptors reveal modest differences in affinities for morphine and naloxone in COS cells but not CHO cells. Ligand‐selectivity profiles of the rat and human mu; receptors were otherwise similar. Interesting differences between these data and data previously obtained with the peptide agonist [3H]DAMGO suggest that the peptide and alkaloid agonists may label different domains of the μ receptor. © 1995 Wiley‐Liss, Inc.1This article is a US Government work and as such, is in the public dom

ISSN:0887-4476    

DOI:10.1002/syn.890210109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe subcellular localization of synaptophysin was investigated in noradrenergic nerve terminals of bovine vas deferens and dog spleen and compared with membrane‐bound and soluble markers of noradrenergic storage vesicles. At the light microscopical level chromogranin A‐ and cytochrome b561‐ immunoreactivity revealed an identical and very dense innervation of the entire vas deferens. In the case of synaptophysin, most immunoreactivity was found only in the outmost varicosities closest to the lumen, which were also positive for chromogranin A. Small dense‐core vesicles of dog spleen were purified using a combination of velocity gradient centrifugation and size exclusion chromatography. Small dense‐core vesicles were enriched 64 times as measured by the noradrenaline content. Enrichments for dopamine‐β‐hydroxylase were in a similar range. Synaptophysin‐containing vesicles were smaller in size and they did not contain the typical noradrenergic markers dopamine‐β‐hydroxylase, cytochrome b561, and noradrenaline. Instead, they might store adenosine triphosphate (ATP). A greater part of synaptophysin immunoreactivity was consistently found at high sucrose densities at the position of large dense‐core vesicles. © 1995 Wiley‐Liss, Inc.We conclude that in the noradrenergic nerve terminal: (1) small dense‐core vesicles have a membrane composition similar to large dense‐core vesicles, indicating that the former are derived from the latter; and (2) synaptophysin seems not to be present on small dense‐core vesicles. We suggest the possibility that synaptophysin‐containing vesicles form a residual population whose role in neurotransmission has been taken over by large and small densecore vesicles follo

ISSN:0887-4476    

DOI:10.1002/syn.890210110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractABT 200 [(RR,SS)‐3‐phenyl‐l‐[l′,2′,3′,4′‐tetrahydro‐5′,6′‐methylenedi‐ oxy‐1′‐naphthalenyl‐methyl]‐pyrrolidine methanesulfonate]is a potent alpha2‐adrenoceptor antagonist (Ki = 1.2 nM) with modest norepinephrine uptake‐blocking activity (IC50= 841 nM) that is currently under clinical evaluation as an antidepressant. The effects of ABT 200, nomifensine (an inhibitor of catecholamine uptake), and rauwolscine (a selective alpha2‐adrenoceptor antagonist) on the clearance of exogenous norepinephrine in the cerebellum of urethane‐anesthetized rats was investigated using a vivo electrochemistry. Chronoamperometric recordings were continuously made at 5 Hz using Nafion‐coated, single carbon fiber electrodes. When a calibrated amount of norepinephrine was pressure‐ejected at 5‐min intervals from a micropipette adjacent (290–330 μM) to the electrode, transient and reproducible norepinephrine signals were detected. In response to systemic ABT 200 (30 mg/kg i.p.) or nomifensine (30 mg/kg i.p.1, the signals increased in both amplitude and time course, indicating significant inhibition of the norepinephrine transporter. A lower dose (15 mg/kg i.p.) of either ABT 200 or nomifensine had no effect in this paradigm. Local application of ABT 200 (400 μM) or nomifensine (400 μM) prior to pressure‐ejection of norepinephrine also significantly increased the amplitude and time course of the norepinephrine signals. In contrast, systemic administration of rauwolscine (30 mgkg i.p.) or vehicle solution, and local application of vehicle solution, had no effect on the norepinephrine signals. These data indicate that at the higher dose evaluated, both ABT 200 and nomifensine inhibit cerebe

ISSN:0887-4476    

DOI:10.1002/syn.890210111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY