摘要:

BASIC fibroblast growth factor (bFGF)-like localization was studied immunohistochemically in the lower auditory tract of neonatal and adult rats. During the neonatal period, bFGF-like immunoreactivity is present in the cytoplasm of inner hair cells, spiral ganglion cells, Scarpa's ganglion cells, in auditory brain stem nuclei and in vestibular nuclei. At the adult stage, bFGF-like protein is widely distributed in the auditory brain stem but was not found in the cochlea. These results suggest that bFGF could be implicated in the development as well as in the neuronal maintenance and plasticity of the auditory system.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

THE expression of mRNAs encoding five putative non-NMDA glutamate receptors was investigated usingin situhybridization with radiolabeled riboprobes. Hybridization was observed in spiral ganglion neurons with probes complementary to mRNA products of the glutamate receptor genes GluR2 and GluR3. No specific hybridization was observed with probes for GluRl, GluR4 or GluR5. The results support the hypothesis that glutamate is the transmitter between cochlear inner hair cells and spiral ganglion neurons, and that it acts via non-NMDA glutamate receptors.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

WE reported previously that injury discharge (ID), a burst of impulses fired following nerve injury, plays a role in triggering autotomy, a neuropathic pain-related behavior in rats. Here we affirm this link using two lines of rats, derived by selective breeding from the Sabra strain to express high (HA) or low (LA) levels of autotomy following hindpaw denervation. Blocking ID in HA rats before injury suppressed autotomy. Correspondingly, artificial prolongation of ID in LA rats just prior to neurectomy, increased autotomy. The autotomy in these HA and LA rats was like that of their Sabra ancestors. This suggests that the underlying basis for selection of these lines was differential sensitivity of the CNS to the effects of ID.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

WE investigated whetherin vivoexcitotoxicity was mediated by a mechanism of programmed cell death called apoptosis. Neurotoxic doses of kainic acid (1.2 nmol) and quinolinic acid (120 nmol) were unilaterally injected in the dorsal hippocampus of anesthetized rats. Eight or 16 h later the animals were killed and DNA was extracted from the injected hippocampi. DNA from mouse thy mocy tes exposed to methylprednisolone (10-5M for 6 h at 37°C) was used as a positive control of apoptotic cells. No typical ‘ladder’ of DNA fragments (multimers of approximately 200 Kb) which characterizes apoptosis was seen in hippocampal cells after toxic doses of kainic or quinolinic acid, as assessed by agarose gel electrophoresis. This suggests that hippocampal nerve cell death inducedin vivoby the excitotoxins is not mediated by apoptosis.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

LEVELS of the acetyicholine receptor (AChR) α-subunit mRNA were quantified in chick leg muscle, both after section of the sciatic nerve and following electrical stimulation of the denervated leg musculature. Whereas a lag period of approximately 17 h intervenes between the nerve section and the increase in message level, electrical stimulation leads to an immediate decline, which proceeds with a half-life of 3–4 h, similar to the decay induced by treatment with actinomycin D. The asymmetry in the kinetics of activation and repression can be accommodated by several regulatory schemes of which the simplest contains an autocatalytic loop as recently proposed by Changeux (The New Biologist3:413–429,1991)

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

NITRIC oxide (NO) is a novel messenger molecule that is produced following glutamate receptor activation and which stimulates cyclic GMP (cGMP) formation. To determine if the mode of action of NO is predominantly intra- or inter-cellular in intact brain tissue, we tested the ability of haemoglobin (Hb), a NO-binding protein that remains extracellular, to inhibit cGMP accumulation induced by glutamate receptor agonists in adult rat cerebellar slices. Responses to agonists acting selectively onN-methyl-D-aspartate (NMDA) and non-NMDA glutamate receptors were inhibited by Hb (IC50± 20 μM) suggesting that NO functions predominantly as a mediator of communication between cells. The effects of NO-donating drugs (e.g. nitroprusside) were also inhibited by Hb, implying that they yield NO extracellularly.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

BOTH extracellular guanosine and adenosine stimulated astrocyte proliferationin vitroand increased intracellular cAMP 6–fold within 2 min. The effects of both guanosine and adenosine on proliferation and cAMP levels were inhibited by antagonists of adenosine A2receptors but augmented by A1receptor antagonists. The correlation between cAMP accumulation and stimulation of cell proliferation by adenosine and guanosine indicates that increased intracellular cAMP may be one of the second messengers involved in these effects. Guanosine is not an adenosine A2receptor agonist and does not activate adenylate cyclase. It may exert its effects indirectly by increasing the endogenous extracellular adenosine concentration.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

DESMETHYLIMIPRAMINE (DMI) has been shown to interact with the N-methyl-D-aspartate (NMDA) receptor complex. Its probable action is through blockade of the cationic channel at the phencyclidine site and as a result it has potential anticonvulsant action. In this present study we have investigated the effects of DMI and ketamine on both NMDA-induced and spontaneous depolarizing shifts in cortical wedges prepared from genetically epilepsy-prone mice (DBA/2). Contrary to published reports, DMI potentiated the effects of NMDA and increased the frequency of spontaneous depolarizations. The actions of ketamine were inhibitory and these were reversed by DMI. Presynaptic mechanisms may be involved in the DMI-induced potentiation and this may explain the lowering of convulsive thresholds seen clinically with tricyclic antidepressants.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

RATS lesioned in one substantia nigra were treated on three consecutive days with the nonselective dopamine agonist, apomorphine (0.05 mg kg-1), the selective D2 agonist, quinpirole (0.025, 0.05, or 0.2 mg kg-1) or the selective D1 agonist, SKF-38393 (2.0, 4.0 or 8.0 mg kg-1). Each of these compounds resulted in acute contralateral rotation which increased significantly upon successive administrations. Two weeks after apomorphine treatment rats exhibited rapid contralateral rotation when placed, undrugged, in the drug-associated environment. Similar undrugged rotation was seen ten weeks after the lower doses of SKF-38393. No evidence of undrugged rotation was seen after quinpirole. The results show that sensitization does not necessarily predict development of a placebo effect, and suggest that persistent motor effects of dopamine agonists are associated with D1 receptor stimulation.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

WE have studied the effects of intracellular cyclic AMP (cAMP) on the response to N-methyl-D-aspartate (NMDA) in hippocampal cultured neurons by loading them with 2'-o-dibutyryladenosine 3', 5'-cyclic monophosphate (dcAMP) and have obtained evidence for regulation of Ca2+release from intracellular stores by cAMP. Extracellular Ringer's solution was either Ca2+-containing or Ca2+-free. A brief initial stimulation with NMDA(10–100 μM, 12 s) was required before the neurons were loaded with dcAMP to potentiate the changes in intracellular Ca2+concentration induced by the second stimulus of NMDA. Forskolin (10 μM) mimicked dcAMP, but to a lesser extent. A phorbol ester 12-o-tetra-decanoylphorbol-13-acetate (100 ±M) inhibited the effect of dcAMP.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID