摘要:

RECENT PET imaging and brain lesion studies in humans are integrated with new basic research findings at the cellular level in animals to explain how the formal cognitive features of dreaming may be the combined product of a shift in neuromodulatory balance of the brain and a related redistribution of regional blood flow. The human PET data indicate a preferential activation in REM of the pontine brain stem and of limbic and paralimbic cortical structures involved in mediating emotion and a corresponding deactivation of dorsolateral prefrontal cortical structures involved in the executive and mnemonic aspects of cognition. The pontine brainstem mechanisms controlling the neuromodulatory balance of the brain in rats and cats include noradrenergic and serotonergic influences which enhance waking and impede REM via anticholinergic mechanisms and cholinergic mechanisms which are essential to REM sleep and only come into full play when the serotonergic and noradrenergic systems are inhibited. In REM, the brain thus becomes activated but processes its internally generated data in a manner quite different from that of waking.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

FOLLOWING axotomy most medial septal neurons in the adult rat brain have dramatically reduced numbers of choline acetyltransferase (ChAT) positive neurons. Since leukemia inhibitory factor (LIF) promotes cholinergic expression in several neuronal populations, the aim of this study was to determine if LIF would continue to support cholinergic expression in axotomized medial septal neurons. Mini-osmotic pumps were used to infuse saline or LIF into the lateral cerebral ventricle. Counts of ChAT and low-affinity nerve growth factor (p75NGFR) immunostained neurons indicated that LIF-treated animals retained ChAT expression in > 90% of axotomized neurons whereas in saline-infused animals this was < 30%. Also, LIF was equally effective in maintaining p75NGFR expression levels in axotomized medial septal neurons.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THIS study was conducted to determine whether nitric oxide (NO) is involved in the maintenance of behavioral signs of neuropathic pain induced by tightly ligating the left L5 and L6 spinal nerves. Neuropathic rats showed behavioral signs representing mechanical allodynia, cold allodynia and cold-stress exacerbated ongoing pain. Mechanical allodynia was suppressed by Nω-nitro-L-arginine methyl ester (L-NAME; 200, 100, 50, 10μM/kg, i.p.), a nitric oxide synthase inhibitor, in a dose-dependent manner. Cold allodynia and cold-stress exacerbated ongoing pain was also attenuated by L-NAME. Neither Nω-nitro-D-arginine methyl ester (D-NAME; 200μM/kg) nor saline changed any of the neuropathic pain behaviors. These results suggested that NO plays an important role in the maintenance of the behavioral signs of neuropathic pain and is involved in common steps in the maintenance of the different modalities of pain such as mechanical allodynia and cold allodynia.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE nucleus tractus solitarius (NTS) plays a crucial role in the reflex control of sympathetic tone through direct projections to the caudal and rostral regions of the ventrolateral medulla (CVLM and RVLM respectively). 5-HT3receptor stimulation in the NTS increases both blood pressure and sympathetic tone. In order to investigate whether the ventrolateral medulla participates in these effects, the expression of c-Fos protein, a marker of neuronal activation, was examined at this level after intra-NTS microinjections of 1-(m-chlorophenyl) biguanide, a selective 5-HT3receptor agonist. A marked increase (93%) in the density of c-Fos-immuunoreactive neurons was restricted to the most rostral part of the RVLM after this treatment. This effect could be prevented by prior intra-NTS microinjection of ondansetron, a selective 5-HT3antagonist. These results suggest the participation of sympathoexcitatory neurons in the rostral RVLM in the pressor response to 5-HT3receptor stimulation in the NTS.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

TWO sets of chimeras between alphaxalone-sensitive GABAAreceptor a α2or β1subunits and the alphaxalone-insensitive glycine receptor a α1subunit were constructed to determine the structural domains important for the modulatory actions of neuroactive steroids. These data suggest that the site of action for neurosteroids on GABAAreceptors is not the same as that for volatile anesthetics and ethanol, but is on the N-terminal side of the middle of TM2.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ANTISERA were raised against endomorphin-2, a recently isolated endogenous opioid peptide that binds potently and selectively to the μ-opioid receptor. When sections of spinal cord were stained immunocytochemically, a dense plexus of fibres and varicosities was visualized in the superficial dorsal horn of rats and one monkey. Following unilateral multiple dorsal rhizotomy, labeling for endomorphin-2 was markedly reduced ipsilateral to the lesion. In sections stained for both endomorphin-2 and CGRP, double-labeling was observed. Taken together, these data suggest that endomorphin-2 occurs in small diameter primary afferent fibres in rodents and primates. It appears possible that the release of neurotransmitters from nociceptive primary afferents might be regulated by release of endomorphin-2 from primary afferent terminals.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

MICROTUBULE-ASSOCIATED proteins (MAPs) are involved in the maintenance of mature neuronal morphology, neurite outgrowth and neuronal plasticity. Alteration in MAP expression may underlie neuronal structural changes in response to seizure activity. The aim of the present study was to investigate whether electroconvulsive shock (ECS), an animal model of electroconvulsive therapy (ECT) in clinical treatment of depression, affected gene expression of MAPs in the rat brain. Usingin situhybridization, we studied the expression of encoding mRNA for MAPs in the brains of rats treated with ECS 5 times over 10 days. The abundance of mRNA encoding microtubule-associated protein 2 (MAP2), a dendritic MAP, was significantly increased (142% compared with controls) in the dentate gyrus 6 and 24 h after the last shock, and had returned to baseline levels within 48 h. These changes were confined to the dentate gyrus no significant changes were observed in CA1 and CA3 of the hippocampus. The increase in MAP2 expression was accompanied by an increase in MAP2 immunoreactivity in the molecular layer of the dentate gyrus. The abundance of mRNA encoding for tau, an axon-specific MAP, and MAP1B, an embryonic MAP, was unaffected by ECS. These data demonstrate that ECS specifically altered the mRNA and protein expression of MAP2 but had no effect on tau or MAP1B, and suggest that changes in MAP2 expression may be related to morphological changes in the dentate gyrus, particularly in the dendrites.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE purpose of this study was to examine the role of anticipatory postural adjustments (APAs) in the execution of forward oriented whole body reaching movements. From the standing position, eight healthy subjects were asked to reach an object placed at 45 cm from the feet, at both naturally paced and fast speeds. Electromyographic signals of six antagonistic muscles were analysed in conjunction with centre of mass (CM) displacements, centre of foot pressure displacements and resultant ground reaction forces. Results revealed that APAs created necessary angular momentum of body segments for effective task execution. These results suggest that APAs can initiate movements conducted from a fixed base of support, and in this context do not act solely to stabilize the CM.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

THE contribution of metabotropic glutamate receptors (mGluRs) in the ventral tegmental area (VTA) to the induction of locomotor sensitization by amphetamine (AMPH) was investigated. Rats pre-exposed to AMPH in the VTA showed significantly higher locomotor activity when subsequently tested with a systemic AMPH challenge than rats preexposed to VTA saline. Rats pre-exposed to AMPH but co-injected with the selective mGluR antagonist (RS)-α-methyl-4-carboxyphenylglycine [(RS)-MCPG] did not show this effect. These findings indicate that activation of mGluRs in the VTA is necessary for the induction of locomotor sensitization by AMPH and provide further support for the important role played by excitatory amino acids in this site in the development of sensitization to AMPH.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

ELECTROCONVULSIVE therapy (ECT) is an appropriate clinical model to investigate blood flow during seizures. In this study cerebral blood flow velocity (CBFV) was measured during 40 ECTs in 10 patients by means of transcranial Doppler sonography. EEG was recorded continuously. Under general anesthesia, the pre-convulsive blood flow velocity (Vmean) decreased significantly. After ECT, we measured a dramatic increase in Vmeanwhich was significantly greater in the left MCA than in the right MCA. After termination of seizures, flow velocities returned to baseline levels. The striking increase in cerebral blood flow velocity reflects excessive cerebral metabolism during convulsive neuronal activation. The left hemisphere seems to be more sensitive to electrical stimuli as was indicated by its predominant augmentation of CBFVs.

ISSN:0959-4965    

出版商:OVID    

年代:1998

数据来源: OVID