Showing papers on "Cuneate nucleus published in 2008"

Does reorganization in the cuneate nucleus following neonatal forelimb amputation influence development of anomalous circuits within the somatosensory cortex

Abstract: Neonatal forelimb amputation in rats produces sprouting of sciatic nerve afferent fibers into the cuneate nucleus (CN) and results in 40% of individual CN neurons expressing both forelimb-stump and hindlimb receptive fields. The forelimb-stump region of primary somatosensory cortex (S-I) of these rats contains neurons in layer IV that express both stump and hindlimb receptive fields. However, the source of the aberrant input is the S-I hindlimb region conveyed to the S-I forelimb-stump region via intracortical projections. Although the reorganization in S-I reflects changes in cortical circuitry, it is possible that these in turn are dependent on the CN reorganization. The present study was designed to directly test whether the sprouting of sciatic afferents into the CN is required for expression of the hindlimb inputs in the S-I forelimb-stump field. To inhibit sprouting, neurotrophin-3 (NT-3) was applied to the cut nerves following amputation. At P60 or older, NT-3-treated rats showed minimal sciatic nerve fibers in the CN. Multiunit electrophysiological recordings in the CN of NT-3-treated, amputated rats revealed 6.3% of sites were both stump/hindlimb responsive, compared with 30.5% in saline-treated amputated animals. Evaluation of the S-I following GABA receptor blockade, revealed that the percentage of hindlimb responsive sites in the stump representation of the NT-3-treated rats (34.2%) was not significantly different from that in saline-treated rats (31.5%). These results indicate that brain stem reorganization in the form of sprouting of sciatic afferents into the CN is not necessary for development of anomalous hindlimb receptive fields within the S-I forelimb/stump region.

[Observation on the central afferent pathway of "Guanyuan" (CV 4) under normal and pathological states and the influence of electroacupuncture].

Abstract: Objective To investigate the afferent pathways of "Guanyuan"(CV 4) under normal and pathological states and to observe the effect of electroacupuncture(EA) on them.Methods Twenty-four female SD rats were randomly divided into normal control(NC),NC+EA,ovariectomy(OVX) and OVX+EA groups,with 6 cases in each.Four weeks after OVX,Pseudorabies Virus(PRV,10 μl liquid containing 108 plaque-forming units) was injected into CV4.Thirty minutes after PRV injection,EA(2 Hz,2-3 mA) was applied to CV4 for 30 minutes,once daily for 3 days.Six hours after the third EA treatment,all the rats were perfused transcardially with 4% paraformaldehyde under anesthesia,followed by sampling the brain and spinal cord and cutting into sections(35 μm).Immunohistochemical method(rabbit anti-rat beta-galactosidase) was used to display PRV immunoreactive(PRV-IR) positive neurons.Results 1) After injection of PRV,PRV-IR positive cells widely distributed in the spinal cord(cervical,thoracic and lumbar segments),brain stem(nucleus of solitary tract,cuneate nucleus,gigantocellular reticular nucleus,nucleus of spinal tract of trigeminal nerve,nucleus raphe magnus,locus caeruleus,etc),hypothalamus and cerebral cortex in each group.2) After OVX,apparently fewer PRV-IR positive cells were found in some nuclei as medial septum nucleus(MSN),arcuate nucleus(ARC),diagonal band nucleus(DBN),paraventricular nucleus(PVN) which have close relation with endocrine activity(P0.05);and rarely seen in ventromedial hypothalamus(VMH) and lateral preoptic area(LPO)(P0.01).But in OVX+EA group,PRV-IR positive cells in above regions or nuclei increased significantly(P0.05 or P0.01).No obvious difference was found between NC and NC+EA groups in the number of PRV-IR positive cells(P0.05).Conclusion Following OVX,PRV-IR positive cells in neuroendocrine-related nuclei of hypothalamus reduced significantly in number;EA of "Guanyuan"(CV 4) can promote the recovery of these neurons in above mentioned nuclei.

The milk-ejection reflex in the sheep: an anatomical study on the afferent pathway.

Abstract: Summary The present study is an attempt to reveal the spinal and supra-spinal organization of the ascending branch of the milk-ejection reflex in the ewe by means of a tract-tracing technique. For this purpose, injections of horseradish peroxidase (HRP) were performed into the lateral cervical nucleus (LCN) and into the hypothalamic paraventricular nucleus (PVN). Peroxidase injections into the LCN revealed retrogradely labelled neurons in the medial part of laminae I–III of the ipsilateral L3 and L4 spinal segments, while injections of HRP into the PVN revealed retrogradely labelled cells in the contralateral LCN and the medial cuneate nucleus. Taking into account the results obtained, it is concluded that the transmission of the afferent input from the nipples to the PVN is accomplished by at least two pathways: one employing a single relay station located in the medial cuneate nucleus, and another possessing two relay stations located in the medial part of laminae I–III of the dorsal horn of L3 and L4 spinal segments and in the LCN.