摘要:

AbstractIn this study, we tested the hypothesis that corticotropin‐releasing factor (CRF) and enkephalin (ENK) coexist within restricted brainstem‐cerebellar circuits. Antisera for CRF and ENK were applied simultaneously or to serial sections of adult opossum brain and were processed for fluorescence or peroxidase, antiperoxidase immunohistochemistry, respectively. CRF and ENK were colocalized in (1) climbing fibers within the flocculus and in the cerebellar vermis; (2) fibers with morphological characteristics of simple mossy fiber terminals or climbing fiber glomeruli that were located within the granule cell layer of the vermis underlying the foci of CRF/ENK‐IR climbing fibers;(3) mossy fiber terminals within the flocculus; (4) neuronal perikarya in subnucleus A and C of the medial accessory olive and in the dorsal cap of Kooy, nuclei known to project as climbing fibers; and (5) cell bodies in nucleus propositus, the subtrigeminal reticular nucleus, and the reticular formation, likely origins of CRF/ENK colocalized mossy fibers. The demonstration that single climbing and mossy fibers contain two peptides extends previous studies that have described chemical heterogeneity within cerebellar afferent pathways. Furthermore, these results support suggestions that this heterogeneity may provide a substrate for differential regulation of signal transduction by chemically coded cerebellar affe

ISSN:0887-4476    

DOI:10.1002/syn.890050302

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

年代:1990

数据来源: WILEY

摘要:

AbstractA major target of neurosecretory axons (NSA) is the bassal lamina around fenestrated blood vessels (FBV) in the neural lobe of the pituitary gland. We have posed the question of whether there is nerurovascular specificity. Do mature, regenerating NSA terminate selectively on the FBV of the neural lobe compared with the FBV of other tissues that normally are not innervated by NSA? Three types of tissue were transplanted between inbred Fisher rats. Fragments, about 1 mm3, of pineawl, adrenal medulla, and neural lobe wwere grafted bilaterally to the hypothalamic, retro‐chiasmatic area, which includes bundles of NSA from supraoptic and paraventricular neurosecretrory nuclei exclusively, but no FBV. Two and 4 weeks later, the grafts were prepared for the immunohistochemical localization of NSA and for electron micaroscopy. NSA‐FBV proximity was measured, and the number of NSA, FBV, and of NSA‐FBV associations was counted per surface area of each graft. Regenerating NSA can associate as closely with FBV of other tissues as they can with the FBV of the neural lobe. There does not appear to be specificity with respect to the closeness of association between neurosecretory terminals and fenestrated capillaries. However, the number of these associations is greater in neural lobe grafts than in adrenal or pineal grafts at 4 weeks. The number of FBV is also greatest, in neural lobe grafts at this time, an increase that would provide a greater opportunity for NSA‐FBV assoc

ISSN:0887-4476    

DOI:10.1002/syn.890050303

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of bath‐applied glycine to substantia nigra zona compacta neurons of rat were investigated byintracellular recording techniques in vitro. Superfusion of glycine (1 mM) in the medium hyperpolarized 53% of the neurons recorded with KCI electrodes, whereas 32% of the cells were depolarized. The remaining 15% of neurons was hyperpolarized and then depolarized by the amino acid. In spite of these membrane changes, the action potential firing was depressed. Both hyperpolarization and depolarization were correlated to an outward and an inward current, respectively, when recording in single‐electrode voltage‐clamp mode.In response to bath application of glycine, the neurons showed a concentration‐dependent conductance increase. Micromolar concentrations of glycine (100–300 m̈M) in the superfusion medium produced a membrane hyperpolarization (outward current) in most of the tested cells, whereas millimolar concentration of amino acid could cause depolarization (inward current) in the same neurons.When the recording electrodes contained K acetate, only hyperpolarizations (outward current) were produced. The potential and current changes and the increase in membrane conductance produced by glycine showed little desensitization when neurons were recorded with K acetate electrodes. The mean reversal potential for the membrane hypolarization was –80 mV with intracellular electrodes containing KCI and –84 mV with electrodes containing K acetate. The mean null potential for the depolarizing effect was –46 mV.The reversal potential for the glycinergic responses was shifted to less negative values upon lowering the extracellular concentration of chloride or increasing the extracellular concentration of potassium. Strychnine (1–10 m̈M) reversibly antagonized both the conductance increase and the membrane changes produced by glycine. Bath application of bicuculline (100 m̈M) and picrotxin (200 m̈M) did not affect glycine responses, while depressing the actions of GABA and muscimol.It is concluded the glycine exerts and inhibition on substantia nigra zona compacta neurons by acting on strychnine‐sensitive receptors. The membrane effects produced by glycine result from the activation of a cloride current. In addition, the simultaneous involvement of porassium ions may contribute to the ove

ISSN:0887-4476    

DOI:10.1002/syn.890050304

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of vasopressin on neurons of the rat dorso‐lateral septum (DLS) was studied in brain slices with intracellular microelectrodes. Two out of 13 neurons showed a small depolarization, spontaneous activity, and increased input resistances following a 15 min exposure to 10‐6to 10‐8M vasopressin (VP). These membrane effects disappeared completely within 3–5 min after the application. The remaining DLS neurons treated with these vasopressin concentrations showed an increase in glutamate‐mediated excitatory postsynaptic potentials (EPSPs), evoked by stimulation of the fimbria fibers. As little as 10‐12M VP increase these EPSPsmarkedly in nearly 80% of the cells studied. This increase in most of the cells disappeared within 15 min after the application period, whereas the increase in EPSPsinduced by 10‐10M VP outlasted the peptide application period for more than 30 min. Neither the blockade of GABA‐ergic synaptic inhibition nor the pre‐treatment of the neurons with d(CH2)5‐Tyr(Me)‐arginine vasopressin or 2‐amino‐5‐phosphonovaleric acid (2‐APV), antagonists for the V1 type of vasopressin receptor and NMDA receptors, respectively, interfered with the EPSPspotentiating effect of the peptide. It is concluded that a type of vasopressin receptor other then the V1 type is involved in the long‐lasting potentiation of the primarily non‐NMDA receptor med

ISSN:0887-4476    

DOI:10.1002/syn.890050305

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe distribution of radioiodinated N‐methyl‐4‐(4‐hyroxy‐3‐iodobenzyl)‐1,2,3,6‐tetrahydropyridine (MHTP), an analog of the reportedly nontoxic N‐methyl‐4‐benzyl‐1,2,3,6‐tetrahydropyridine, (4‐homo‐MPTP), has been studied in the primate. [123I]‐MHTP‐derived radioactivity exhibited a progressive accumulation and prolonged retention within the primateeye. Following injection, [123I]MHTP rapidly accumulated within the primate brain and was subssequently oxidized to a radiolabeled metabolite. The half‐life of [123I]MHTP‐derived radioactivity within the primate brain was 50 min. The highest concentrations of radioactivity were found in the caudate‐putamen and the frontal, temproal and cingulate cortices; the substantia nigra and inferior olivary nucleus were labeled with medium intensity. Very low concentrations of radiolabel were detected in the cerebellum and white matter, Selective accumulation of [125I]MHTP‐derived radioactivity within these structures was blocked by pretreatment with pargyline, suggesting that nonoamine oxidase B is involved in

ISSN:0887-4476    

DOI:10.1002/syn.890050306

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe muscarinic cholinergic system has been mapped in vivo inhuman and baboon brain using [N‐11C‐methyl]‐benztropine and high resolution positron emission tomography (PET). [N‐11C‐methyl]‐benztropine uptake was observed in frontal, parietal, occipital, and temporal cortices as well as in subcortical structures including the corpus striatum and thalamus. Uptake continued to increase in baboon and human brain in all areas over an 80 minute experimental period with the exception of the exception of the cerebellum wehere the accumulation of radioactivity began to decrease by 25 minutes potinjection. The ratio of incorporation of [N‐11C‐methyl]‐benztropine between corpus striatum/cerebellum was 1.53 and 1.46 in humans and baboons, respectively, at 60 minutes. Blocking studies in baboons using the muscarinic cholinergic antagonists scopolamine and benztropine and the muscarinic cholinergic agonist pilocarpine combined with blocking studies in humans using benztropine indicate that the binding of this compound is specific for the muscarinic cholinergic system. Pretreatment with the potent dopamine reuptake blocker nomifensine produced no effect on the incorporation of radioactivity in any baboon brain region examined. Analysis of labelled plasma metabolites indicates that in humans, the rate of metabolism of [N‐11C‐methyl]‐benztropine is slow (83.0% unchanged at 30 minutes postinjection) differeing quite dramatically from the rate of metabolism observed in baboons (43.4%% unchanged at 30 minutes postinjection). These data combined with postmortem studies in humans and primates demonstrate that [N‐11C‐methyl]‐benztropine is a suitablemuscarinic cholinergic ligand for use i

ISSN:0887-4476    

DOI:10.1002/syn.890050307

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of monocular deprivation, beginning at hatching, were examined in the neuropil of ectostriatum, a visusal telencephalic projection area in birds. The Volume of ectostriatum, the number of synapses and subsynaptic features like the presynaptic terminal size and the length of the postsynaptic contact zone were quantified in juvenile (20 d) and adult (100 d) zebra finches. Monocular deprivation affects almost all of the parameters mentioned above in juvenile birds, but only one (i.e., the size of presynaptic terminals) is permanently altered in adulthood. Both hemispheres are affected in juvenile birds with respect to the volume of ectostriatum, the length of synaptic contact zones and the presynaptic terminal size when compared to normal values. In normal birds the number of synaptic contacts is established at 20 days and remains fairly constant at 100 days. In experimental birds there is an increase in synapse number during this time period. However, no interhemispheric differences or differences compared to normal animals could be identified. The presynaptic terminals in experimental birds are smallercompared to normal values in young (25% for the deprived side; 19% for the non‐deprived side) and adult (13% for the deprived side; 11% for the non‐deprived side) animals. The only permanent effect caused by monocular deprivation in the ectostriatum is characterized by smaller presynaptic terminals. It is surprising that the tectofugal pathway that is believed to be mostly ipsilateral is not very vulnerable to monocular deprivation in adult animals. It is even more surprising that the deprivation effects are seen on both sides of the brain. The implications of this plasticity will be discussed in this pa

ISSN:0887-4476    

DOI:10.1002/syn.890050308

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

年代:1990

数据来源: WILEY

摘要:

AbstractIntracellualar recordings were made from neurons of vesical parasympathetic ganglia (VPG) isolated from the rabbit urinary bladder and maintained, in vitro. Bath‐application of norepinephrine (NE, 500 mM–5 m̈M) caused a hyperpolarizing response at the postsynaptic membrane of VPG neurons in a concentration‐dependent manner. NE blocked the action potential elicited by an orthodromic stimulation of preganglionic (pelvic) nerve fibers. AT a relatively low concentration (5–100 nM), NE depressed the fast excitatory postsynaptic potential (EPSP), without producing the hyperpolarization. NE (100 nM) produced 49 ± 17% (N=5) decrease in the amplitude of the fast EPSP. NE did not depress the acetylcholine (ACh) potential produced by iontophoretic application of ACh to the ganglion cells. NE did not affect the amplitude of the miniature EPSP, while it reduced the frequency of miniature EPSPs. These results suggest that NE inhibits the nicotinic transmission in the rabbit VPG, probably reducing theh ACh release from presynaptic nerve terminals. Epinephrine (1 m̈M) was more potent than NE (1 m̈M) in producing the hyperpolarization as well as the blockade of the fast EPSP amplitude. Isoproterenol was ineffective as an agonist for these inhibitory adrenoceptors. Clonidine mimicked the effect of NE on the fast EPSP. Yohimbine and idazoxan antagonized both the inhibition of the fast EPSP and the hyperpolarization produced by NE. These results suggest that α2‐adrenoceptors are responsible for the inhibition of the neuronal activity in parasympathetic ganglia of the rabbit urinary bladder. Immunohistochemical study demonstrated the presence of tyrosine hydroxylase (TH)‐labelled neuronal elements in the VPG. They were a small proportion of principal neurons, their dendrites, and many varicose fibers. TH‐labelled varicosities were often situated in close proximity to the unlabelled principal neurons. TH‐labelled small cells also formed clusters among the prin

ISSN:0887-4476    

DOI:10.1002/syn.890050309

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe activation of cyclic adenosine 3′5′‐monophosphate (cAMP)‐dependent protein kinases has been implicated as an integral mechanism in stimulus‐secretion coupling in the anterior pituitary. Therefore, we have investigated phosphorylation of endogenous protein substrates both in the presence and absence of cAMP in cell‐free extracts of the rodent anterior pituitary. Specific phosphoprotein substrates in the rat anterior pituitary, which are phosphorylated by a cAMP‐dependent protein kinase in vitro, were identified. Cyclic AMP potentiated the phosphorylation of proteins with apparent molecular weights of 85,000, 77,000, 63,000, 39,000, and 33,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE). Proteins with apparent molecular weights of 124,000, 93,000, 48,000, and 43,000 were phosphorylated only in the presence of cAMP and not in the basal condition. The results highlight edogenous protein substrates that may potentially be involved in cAMP‐dependent stimulus‐secretion coupling in the

ISSN:0887-4476    

DOI:10.1002/syn.890050310

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

年代:1990

数据来源: WILEY

摘要:

AbstractCalmodulin is a small, acidic calcium‐binding protein that regulates a number of calcium‐dependent enzyme activities and is thought to be involved in neurotransmission to begin to explore further the regulation of this important protein in the brain, we have cloned a rat calmodulin cDNA and designed an oligonucleotide probe based on this sequence. Both the cDNA and oligonucleotide probes revealed a markedly heterogeneous distribution of hybridization signal for calmodulin mRNA in the rat brain. The greatest apparent abundance of mRNA for calmodulin was seen in the hippocampus and cerebral cortex, whereas many brain regions showed relatively low hybridization signal, including the striatum and portions of the hypothalamus and brains

ISSN:0887-4476    

DOI:10.1002/syn.890050311

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

年代:1990

数据来源: WILEY