Neuroscience
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The present study was to determine how afferents from the substantia nigra pars reticulata (SNr) of the basal ganglia to the pedunculopontine tegmental nucleus (PPN) in the brainstem could contribute to the control of behavioral states. We used anesthetized and acutely decerebrated cats (n=22). Repetitive electrical stimulation (10-100 Hz, 20-50 microA, for 4-20 s) to the ventrolateral part of the PPN produced rapid eye movement (REM) associated with a suppression of postural muscle tone (REM with atonia). ⋯ On the other hand, an injection of muscimol into the dorsolateral part of the SNr (1-15 mM, 0.1-0.25 microl) induced REM with atonia, which was in turn eliminated by a further injection of muscimol into the PPN (5-10 mM, 0.2-0.25 microl). These results suggest that a GABAergic projection from the SNr to the PPN could be involved in the control of REM with atonia, signs which indicate REM sleep. An excessive GABAergic output from the basal ganglia to the PPN in parkinsonian patients may induce sleep disturbances, including a reduction of REM sleep periods and REM sleep behavioral disorders (REM without atonia).
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Comparative Study
Evidence of neuronal excitatory amino acid carrier 1 expression in rat dorsal root ganglion neurons and their central terminals.
The expression and distribution of the neuronal glutamate transporter, excitatory amino acid carrier-1 (EAAC1), are demonstrated in the dorsal root ganglion neurons and their central terminals. Reverse transcriptase-polymerase chain reaction shows expression of EAAC1 mRNA in the dorsal root ganglion. Immunoblotting analysis further confirms existence of EAAC1 protein in this region. ⋯ Unilateral dorsal rhizotomy experiments further show that EAAC1 immunoreactivity is less intense in superficial dorsal horn on the side ipsilateral to the dorsal rhizotomy than on the contralateral side. The results indicate the presence of EAAC1 in the dorsal root ganglion neurons and their central terminals. Our findings suggest that EAAC1 might play an important role in transmission and modulation of nociceptive information via the regulation of pre-synaptically released glutamate.
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Comparative Study
Region specific changes in forebrain 5-hydroxytryptamine1A and 5-hydroxytryptamine2A receptors in isolation-reared rats: an in vitro autoradiography study.
The neurochemical correlates of the behavioural consequences of isolation rearing of rats are complex and involve many neurotransmitters, including the serotonergic system. Impaired functioning of the ascending serotonergic system has been implicated in many neuropsychiatric syndromes, including attention deficit hyperactivity disorder and schizophrenia. In the present investigation serotonergic function was assessed using in vitro receptor autoradiography. ⋯ By contrast, 5-HT(1A) receptor binding site densities were significantly reduced by 22% in the prelimbic cortex, and significantly increased by between 10 and 50% in the motor cortex, somatosensory cortex, dentate gyrus and CA fields of the hippocampus. These data demonstrate that isolation-rearing produces significant effects on forebrain 5-HT(1A) and 5-HT(2A) receptor densities in the adult rat. It is hypothesised that altered serotonergic function, particularly in the hippocampus and prefrontal cortex, may underlie some of the behavioural abnormalities associated with isolation-rearing.
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Comparative Study
The responses of oligodendrocyte precursor cells, astrocytes and microglia to a cortical stab injury, in the brain.
The cortical stab injury has been widely used for biochemical analysis of molecular changes following CNS injury. However, the cellular responses to this injury have not been accurately quantified. In order to provide a baseline for biochemical studies and future experiments on the manipulation of the CNS injury response we have undertaken a quantitative analysis of this injury. ⋯ They are likely to be blood-derived cells that express NG2 or have ingested it. NG2 immunohistochemistry and platelet-derived growth factor alpha receptor (PDGFalpha-R) in situ hybridisation on neighbouring sections was performed. In the lesioned area only 12% of NG2 positive (+ive) cells were PDGFalpha-R +ive (a ratio of 1:8 for PDGFalpha-R +ive cells: NG2 +ive cells) compared with 33% in the unlesioned cortex and an almost 100% overlap in the spinal cord.
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To determine the sensitivity of basal forebrain cholinergic neurons to ionotropic glutamate receptor activation, acetylcholine was collected from the cerebral cortex of urethane-anesthetized rats using microdialysis while monitoring cortical electroencephalographic (EEG) activity. alpha-Amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA; 1, 10, or 100 microM), N-methyl-D-aspartate (NMDA; 100 or 1000 microM) or a combination of AMPA (10 microM) and NMDA (100 microM) was administered to the basal forebrain using reverse microdialysis. Both glutamate receptor agonists produced concentration-dependent, several-fold increases in acetylcholine release indicating that they activated basal forebrain cholinergic neurons; AMPA was more potent, increasing acetylcholine release at a lower concentration than NMDA. The combination of AMPA and NMDA did not produce any greater release than each drug alone, indicating that the effects of these two drugs on cholinergic neurons are not additive. ⋯ The highest concentrations of AMPA and NMDA tested produced small (25%) but significant increases in high frequency activity. There was a positive correlation across animals between the increases in power in the beta (14-30 Hz) and gamma (30-58 Hz) ranges and increases in acetylcholine release. These results indicate that glutamate can activate cholinergic basal forebrain neurons via both AMPA and NMDA ionotropic receptors but has a more modest effect on EEG activation.