摘要:

RECORDINGS of unit activity showing 4–6 ms latency responses to a click stimulus provided evidence that the dentate nucleus could function as a short-latency auditory relay. On the basis of these findings, plus fiber fillings from injections of phaseolus leucoagglutinin into the dentate, a new auditory pathway between dorsal and ventral cochlear nuclei, dentate nucleus, and rostral thalamus is proposed. The pathway could provide direct, short-latency transmissions to the motor cortex that bypass the classical auditory receptive cortex.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

PREVIOUS reports have shown that tolerance or sensitization to apomorphine depends on the dosage interval. The effect of apomorphine on behaviour increases when there is a drug-free period between successive injections. Here we studied the biochemical action of apomorphine during a drug-free period. The experiments showed that dopamine level and dopamine turn-over are persistently inhibited for at least 48 h after apomorphine administration. At 24 h after drug injection, there was a decrease of both DOPAC level and tyrosine hydroxylase activity. The results suggest that apomorphine induces long-lasting dopaminergic inhibition action that increases drug-induced behavioural response, perhaps after development of postsynaptic hypersensitivity.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

RECENT studies indicate that the liquor (CSF)-contacting cell bodies in the periventricular organ of non-mammalian vertebrates accumulates rather than synthesizes dopamine. We therefore gave the lizardGekko geckoinjections of the dopamine synthesis inhibitor alpha-methylparatyrosine (α-MPT). Brains were fixed 105–240 min after injection. Subsequent staining with dopamine antiserum revealed almost no changes in staining in the periventricular organ but there was a dramatic decrease in the other dopaminergic cell groups of the brain. The data support the notion that the cells in the periventricular organ accumulate dopamine and that the CSF plays an important role in dopamine neurotransmission in non-mammalian vertebrates.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

PRESSURE application of the inhibitory neurotransmitters glycine and GABA, respectively, evoked a Cl-current in spinal cord neurons of fetal mice in culture. Memantine, in low concentrations (0.3–5 μM) enhanced the glycine-mediated current at both negative and positive holding potentials. At concentrations of more than 5 μM, memantine increased the glycine-evoked current only when the membrane potential was positive. At negative potentials the current was inhibited. 3-isopropylamantadine and 3,5-diethylamantadine augmented the glycine-activated membrane current irrespective of the concentrations applied, whereas amantadine was ineffective. The GABA-activated Cl-current was not altered by the adamantanes. These data are evidence of a specific glycinergic interaction with putative antispastic agents and can explain some conflicting effects of memantine in experimentally induced seizures.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

IN an attempt to investigate the apparent absolute selectivity of the synaptic vesicle L-glutamate carrier, L- and D-enantiomers of excitatory sulphur-containing amino acid (SAA) transmitter candidates (which are close structural analogues of L-glutamate) were tested for their capacity to compete for vesicular L-[3H]-glutamate uptake. All SAAs inhibited, to varying degrees (52–86%), the vesicular uptake of L-[3H]-glutamate. A similar level of inhibition was exerted by SAAs with either a shorter or equal carbon chain length to L-glutamate. Moreover, inhibition was stereospecific in favour of the D-enantiomers. These studies indicate an appreciable interaction of the SAAs with the recognition site of the vesicular L-glutamate carrier. Further investigations are required to establish the substrate potential of the SAAs.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Low doses of estrogen (E) were given to ovariectomized (OVX) rats and the ventromedial hypothalamic nucleus (VMN) was examined at the ultrastructural level. Administration of 10 μg of E for two consecutive days resulted in an increase in the number of axodendritic synapses in the VMN in comparison to OVX rats treated with oil. The percentage of axospine and multiple synapses and the length of the postsynaptic density were unchanged by E treatment. These results provide further support for the ability of low doses of E to alter neuronal morphology.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

To study the role of muscarinic receptor subtypes in sleep control, methoctramine (25, 50, 75 μg), a highly selective M2antagonist, was injected intra-cerebro-ventricularly into freely moving rats. Methoctramine induced a dose-dependent increase in desynchronized sleep (DS) latency (from 62.7 ± 10 min following saline to 122.4 ± 13.8 min with the lowest dose) and a 75% decrease in the amount of DS in 6 h recordings. 4DAMP (a M3/M1selective antagonist) did not significantly change DS latency and percentage time, but it reduced wakefulness (from 38 ± 2.8% following saline to 25.3 ± 3.7% with a dose of 2.5), and increased slow wave sleep. The results suggest that M2muscarinic receptors play a selective role in DS physiology.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

THE possible involvement of the metabotropic glutamate receptor in mechanisms of hippocampal long-term potentiation was investigated with the new antagonist 2-amino-3-phosphonopropionate (AP3). The action of D-AP3, D,L-AP3 and of the more selective L-isomer was tested on CA1 pyramidal cellsin-vitro. If 100–300 μM of L- or D,L-AP3 was present during tetanization, post-tetanic and early long-term potentiation developed almost normally. However, starting from 100 min, LTP of the field-EPSP was eliminated in an irreversible manner. In contrast to the L-isomer, D-AP3 did not influence the course of LTP. These data suggest that the activation of the metabotropic glutamate receptor is necessary for subsequent mechanisms enabling the late maintenance of LTP.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

IN this study on guinea pig hippocampal slices, protein kinase C (PKC) involvement in long-term potentiation (LTP) of GABAAand GABABreceptor-mediated fast and slow IPSPS, respectively, was examined. Stimulation of the stratum radiatum induced EPSPs followed by fast and slow IPSPs in the CA1 neurons. Tetanic stimulation of the stratum caused a marginal LTP of the fast IPSP but not of the slow IPSP. When K-252b, a potent inhibitor of PKC, was injected into CA1 neurons, LTP of fast and slow IPSPs was observed. These results indicate that PKC activation in CA1 neurons is involved in minimizing, rather than inducing, LTP of the IPSPSso that the EPSP is not distorted.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

AN input-dependent increase in postsynaptic Ca2+mayplay a role in long-term potentiation (LTP) of synaptic transmission while no or subthreshold increase in Ca2+is associated with long-term depression (LTD) in the developing visual cortex. To see whether LTD is induced only at tetanized synapses, a Ca2+-chelator was injected into layer 2/3 neurons in cortical slices from young rats, and excitatory postsynaptic potentials (EPSPs) of these cells, after test stimulation of the white matter and layer 1/2, were observed before and after tetanic stimulation of the former site. The chelator injection led to LTD of EPSPs at tetanized synapses, but no changes were seen at non-tetanized synapses. These results suggest that tetanic inputs induce LTD at tetanized synapses when they are associated with no or subtle increase in postsynaptic Ca2+.

ISSN:0959-4965    

出版商:OVID    

年代:1991

数据来源: OVID