Neuroscience research
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Neuroscience research · Oct 2007
Inhibition of glutamatergic transmission by morphine in the basolateral amygdaloid nucleus reduces pain-induced aversion.
We examined the role of glutamatergic transmission within the basolateral amygdaloid nucleus (BLA) in pain-induced aversion using a conditioned place paradigm and an in vivo microdialysis technique in rats. Microinjection of MK-801 (1 or 10 nmol/side) into the bilateral BLA 5 min before intraplantar injection of formalin dose-dependently attenuated formalin-induced conditioned place aversion (F-CPA) without affecting nociceptive behaviors, such as lifting, licking, and biting. On the contrary, microinjection of neither CNQX (30 nmol/side) nor AP-3 (30 nmol/side) showed any significant effect on F-CPA. ⋯ This increase in glutamate was suppressed by morphine perfusion (100 microM) via the microdialysis probe. Moreover, intra-BLA injection of morphine (10 microg/side) 5 min before formalin injection attenuated F-CPA without affecting nociceptive behaviors. These results suggest that glutamatergic transmission via NMDA receptors in the BLA plays a crucial role in the pain-induced aversion, and that in addition to the well-characterized effects on the sensory component of pain, morphine also influences the affective component of pain through an inhibitory effect on intra-BLA glutamatergic transmission.
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Neuroscience research · Sep 2007
Immunohistochemical detection of L-DOPA-derived dopamine within serotonergic fibers in the striatum and the substantia nigra pars reticulata in Parkinsonian model rats.
On the basis of our previous studies in the normal rat [Arai, R., Karasawa, N., Geffard, M., Nagatsu, I., 1995. L-DOPA is converted to dopamine in serotonergic fibers of the striatum of the rat: a double-labeling immunofluorescence study. Neurosci. ⋯ Using a dual immunofluorescence histochemistry, we examined DA-immunoreactivity in the 5-HT fibers within the ST and the SNR of the PD model rats after L-DOPA was injected intraperitoneally. In experimental cases with the L-DOPA administration, DA-immunoreactivity was detected in 5-HT fibers in both the ST and the SNR on the 6-OHDA injection side; no DA-immunoreactivity was found in 5-HT fibers in the ST or the SNR in control cases without the L-DOPA administration. The results support the assumption that exogenously administered L-DOPA may be converted into DA within the 5-HT fibers in the ST and SNR of the PD model rats.
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Neuroscience research · Aug 2007
Expression of free fatty acid receptor GPR40 in the central nervous system of adult monkeys.
The G-protein coupled receptor 40 (GRP40) is a transmembrane receptor for free fatty acids, and is known for its relation to insulin secretion in the pancreas. Recent studies demonstrated that spatial memory and hippocampal long-term potentiation of rodents and cognitive function of humans are improved by a dietary supplementation with arachidonic and/or docosahexaenoic acids, which are possible ligands for GPR40. While free fatty acid effects on the brain might be related to GPR40 activation, the role of GPR40 in the central nervous system (CNS) is at present not known. ⋯ GPR40 immunoreactivity of was observed in the nuclei and/or perikarya of a wide variety of neurons including neurons in the cerebral cortex, hippocampus, amygdala, hypothalamus, cerebellum, spinal cord. In addition, astrocytes of the cerebral white matter, the molecular layer and multiform layer of the cerebral cortex, the subventricular zone along the anterior horn of the lateral ventricle, and the subgranular zone of the hippocampal dentate gyrus showed GPR40 immunoreactivity. The present data first provide a morphological basis for clarifying the role of GPR40 in the primate CNS.
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Neuroscience research · Jul 2007
Involvement of substance P and calcitonin gene-related peptide in development and maintenance of neuropathic pain from spinal nerve injury model of rat.
Recently, it has been suggested that uninjured primary sensory neurons contribute to neuropathic pain induced by peripheral nerve injury. However, there is lack of evidences of roles of normal pain transmitting substances such as substance P and calcitonin gene-related peptide (CGRP) in neuropathic pain. Whether substance P and CGRP have a role in spinal nerve-injured neuropathic pain model was tested. ⋯ The treatments with lidocaine, L703,606 and CGRP8-37 delayed the onset of neuropathic pain by 1-4 days, compared with the saline-treated rats. After neuropathic pain was established, intrathecal injections of L703,606 and CGRP8-37 significantly mitigated mechanical hyperalgesia for 20 min. These results suggest that substance P and CGRP are involved in the development and maintenance of neuropathic pain and that these peptides from the central terminals of intact sensory neurons contribute to the maintenance of peripheral nerve injury-induced neuropathic pain.
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Neuroscience research · May 2007
Comparative StudySpinal cord stimulation modulates intraspinal colorectal visceroreceptive transmission in rats.
Previous studies have shown that spinal cord stimulation (SCS) of upper lumbar segments decreases visceromotor responses to mechanical stimuli in a sensitized rat colon and reduces symptoms of irritable bowel syndrome in patients. SCS applied to the upper cervical spinal dorsal column reduces pain of chronic refractory angina. Further, chemical stimulation of C1-C2 propriospinal neurons in rats modulates the responses of lumbosacral spinal neurons to colorectal distension. ⋯ However, L2-L3 or C1-C2 SCS did not significantly affect inhibitory neuronal responses to CRD. C1-C2 SCS-induced effects were abolished by cutting the C7-C8 dorsal column but not by spinal transection at cervicomedullary junction. These data demonstrated that upper cervical or lumbar SCS modulated responses of lumbosacral spinal neurons to noxious mechanical stimulation of the colon, thereby, proved two loci for a potential therapeutic effect of SCS in patients with irritable bowel syndrome and other colonic disorders.