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At least 919 records · Page 51Linked to original sources
PubMed1992

Quantitative autoradiographic localization of [125I]neuropeptide Y receptor binding sites in rat spinal cord and the effects of neonatal capsaicin, dorsal rhizotomy and peripheral axotomy.

Using in vitro quantitative receptor autoradiography the present study reports on the distribution and possible changes of [125I]neuropeptide Y (NPY) binding sites in the rat spinal cord following neonatal capsaicin treatment, dorsal rhizotomy and sciatic nerve section. In control spinal cord the highest density of [125I]NPY binding sites was noticed in the superficial layers of the dorsal horn whereas low-to-moderate densities of [125I]NPY binding sites were detected in the deeper dorsal horn and in the ventral horn. In comparison with control rats, neonatally treated capsaicin rats showed a significant (P less than 0.001) bilateral decrease in [125I]NPY binding sites in the superficial layers of the dorsal horn. Unilateral dorsal rhizotomy and unilateral sciatic nerve section also exhibited a significant (P less than 0.05) depletion in [125I]NPY labeling in the superficial layers of the dorsal horn ipsilateral to the surgery. These results suggest that a certain proportion of [125I]NPY receptor sites is located on the primary afferent fibers of the superficial layers of the dorsal horn. This peptide thus could play an important role in the modulation of nociceptive transmission by acting directly on primary afferent terminals.

Animals↗
PubMed1993

In goldfish the qualitative discriminative ability for odors rapidly returns after bilateral nerve axotomy and lateral olfactory tract transection.

After amino acid discrimination training (Arg vs. Gln) in 5 groups of 2 fish the olfactory nerves and in 5 groups the lateral olfactory tracts were intracranially and bilaterally dissected. Immediately after this operation both groups of fish were unable to discriminate concentration differences and contaminated stimuli. Two weeks after the operation, following functional regeneration, both groups again were able to discriminate stimulus concentration differences and contaminations as they did before the operation. Therefore functional regeneration of the olfactory nerves (peripheral regeneration) and lateral olfactory subtracts (central regeneration) is highly specific.

Animals↗
PubMed1983

Long-lasting facilitation of a monosynaptic pathway as a result of "partial" axotomy of its presynaptic elements.

We investigated the long-lasting effects of severing an axonal branch on the function of the synapses made by the remaining branches of the "partially" transected axon. The experimental model used was the monosynaptic reflex pathway of the cat lumbar cord. Preliminary surgical procedures consisted of a dorsal column (DC) hemisection at the L3--L4 level on the left side under aseptic conditions. During the final recording experiments, the monosynaptic reflex (MSR) of the operated and normal (control) side was studied in motorpools in the L7 and S1 segments. The results indicate that the DC operation produced on the operated side (a) an enhancement of the MSR and (b) a more powerful postetanic potentiation, both of the "early" and "late" varieties. These effects were seen as early as 34 days and as late as 121 days after the original DC hemisection. Control experiments were carried out to exclude denervation supersensitivity, supraspinal effects, and normal asymmetries between sides as the mechanism underlying these effects. A presynaptic change in the operated axons, resulting in an increased synaptic efficiency, is proposed as the possible mechanism.

Animals↗
PubMed1985

Role of the interval between axotomy and nerve suture on the success of muscle reinnervation: an experimental study in the rabbit.

The influence of the time interval between nerve transection and neurorrhaphy on motor and sensory reinnervation was studied experimentally in the rabbit. We evaluated the maximal tetanic tension, the amplitude of the compound action potential, and the retrograde transport of horseradish peroxidase 30 and 60 days after neurorrhaphy carried out at 0, 10, or 20 days after transection of the nerves to the medial and lateral gastrocnemius and soleus muscles. The results showed that the suture 20 days after transection was followed by a more precocious motor reinnervation, whereas the outgrowth of motor axons past the suture was not affected by the time interval between transection and neurorrhaphy. On the contrary, the best regrowth of afferent axons was obtained after an interval of 10 days between transection and suture. We conclude that the time interval did not influence motor axon growth, but was involved in the operation of mechanism(s) involved in the reestablishment of impulse conduction and/or synaptic efficacy. In contrast, the time interval appeared to be related to factors involved directly in the axonal elongation of afferent fibers.

Action Potentials↗
PubMed1988

The fate of prelabeled Clarke's column neurons after axotomy.

We studied Clarke's Column of the L-1 spinal cord segment of young adult female rats after first prelabeling its neurons by the intracerebellar injection of Fluoro-Gold or true blue and subsequently axotomizing the labeled cells by a complete spinal cord transection at T-9. In control rats, the number of labeled neurons at 1, 5, 10, and 20 weeks showed a progressive decrease, probably due to leakage of dye from the cells. A much greater loss of labeled neurons was found in T-9 spinal cord-transected rats than in their matched controls. At 5 weeks after transection, loss of large neurons was somewhat offset by an increase in small neurons; neuron shrinkage was a likely cause of this increase, because small, very intensely labeled neurons were found in transected rats but not in control rats. By 10 and 20 weeks post-transection, the number of all prelabeled neurons in transected rats had sharply decreased. In transected rats, but not in controls, very significant increases in labeled astroglia and microglia and other labeled small cells were found at 5 weeks. At 10 weeks, the identifiable labeled astroglia had decreased but marked increases in microglia and other labeled small cells persisted. We conclude that, following a complete T-9 spinal cord transection, axotomized Clarke's column neurons first shrink in size and then die. Labeled reactive astrocytes, which are most evident 5 weeks after injury, probably indicate phagocytosis of axotomized neurons.

Animals↗
PubMed1990

Axotomy enhances the outgrowth of neurites from embryonic rat septal-basal forebrain neurons on a laminin substratum.

Previous studies have suggested that embryonic (nonaxotomized) and regenerating central nervous system neurons differentially respond to the same substrata. In the present study, we have used an in vitro model to test the ability of laminin and type I collagen to promote the outgrowth of neurites from nonaxotomized and axotomized, embryonic septal-basal forebrain (SBF) neurons. Neurons within explants derived from Embryonic Day (E) 15 rats extended neurites that demonstrated similar growth characteristics on a collagen or laminin substratum. E15 neurons could be induced to extend longer neurites on laminin if they were axotomized in vitro and subsequently replated onto a laminin substratum. The carbocyanine dye DiI indicated that neurons which were axotomized could survive and regenerate processes. These regenerating neurites grew 27% longer on laminin than they did on collagen. Similarly, neurons that were axotomized in situ, i.e., E18 SBF neurons, extended neurites that were 29% longer on a laminin substratum. In contrast, E15 explants that were maintained in suspension culture prior to being plated onto a substratum exhibited similar growth on laminin or collagen. The increase in regeneration by E15 neurons on laminin was augmented, by 22%, if nerve growth factor was supplemented to the culture medium. These results demonstrate that laminin is a better substratum, as compared to collagen, for the elongation of neurites from axotomized SBF neurons. Nonaxotomized neurites, on the other hand, do not appear to prefer one substratum over the other. Furthermore, regeneration from embryonic, SBF neurons on laminin is augmented if NGF is used simultaneously.

Animals↗