Chemical sensory deafferentation abolishes hypothalamic pituitary activation induced by noxious stimulation or electroacupuncture but only decreases that caused by immobilization stress. A c-fos study
Section snippets
Experimental procedures
The regulations of local authorities in handling laboratory animals, and the guidelines of the European Communities Council Directive of 24 November 1986 (86/609/EEC), were followed.
Animal behaviour
There were no differences between intact, vehicle- or capsaicin-treated animals during restraint trials, both being quiet during the first minutes of restraint and later struggling intermittently against the forced immobilization. In animals anaesthetized before somatosensory stimulation, there were no motor or vocal reactions to stimulation. As usual, electrical pulses during acupuncture caused gentle rhythmic contractions of local hindleg muscles.
Central nervous system
In unstimulated controls, Fos-IR cells
Neurotoxic action of capsaicin
Neonatal subcutaneous capsaicin, at a dose of 50 mg/kg, causes a massive reduction (95%) of the number of unmyelinated C-fibres in rat dorsal roots[36]extending to less than 40% of the thin myelinated Aδ-fibres.[37]This is accompanied by the virtual disappearance of substance P (SP) and other peptides[35]from lamina I–II of the superficial dorsal horn in which most unmyelinated afferents terminate.[29]In accordance with the fact that noxious input is mostly conveyed by C-fibres,[47]a long-term
Conclusions
The results show that activation of the HPA by noxious stimuli in anaesthetized animals depends entirely on the nociceptive input elicited in primary somatosensory afferents. The effects of EA on the HPA were similar to those of noxious stimulation, and like them totally blocked by capsaicin. Therefore EA action on the HPA also depends on the excitation of nociceptive primary afferents. The somatosensory input provoked by both types of stimulation was likely to reach the HPA through the caudal
Acknowledgements
The authors are grateful to Prof. M. D. Madeira, the Anatomy Department of the Faculty of Medicine of Oporto, for help with the stereological evaluation of the PVN, Dr Maria Eugenia Azevedo, Radio-Isotope Laboratory, for the hormone assays, and Prof. Altamiro Costa-Pereira, the Biostatistics and Medical Informatics Department, for help with the statistical work. Dr B. Pan was the recipient of a scholarship from the PRAXIS XXI Program, Lisbon. This work was supported by JNICT research grant
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ACUPUNCTURE AND PAIN
2019, Revista Medica Clinica Las CondesLithium-induced malaise does not interfere with adaptation of the hypothalamic-pituitary-adrenal axis to stress
2017, Progress in Neuro-Psychopharmacology and Biological PsychiatryCitation Excerpt :Unfortunately, the specific signals involved in the activation of the physiological stress response by different types of stressors have not been thoroughly characterized. In this regard, IMO-induced c-fos expression in several brain areas, including the PVN, was reduced after treatment of young rats with capsaicin that damage type C fibers and thus impairs interoceptive signal entering the nucleus of the solitary tract (Pan et al., 1997). However, C fibers carry out not only all types of visceral signals but also pain-related signals, making it difficult to know the precise type of signals contributing to HPA activation.
Acupuncture stimulation and neuroendocrine regulation
2013, International Review of NeurobiologyCitation Excerpt :There was no increase in c-fos expression in the paraventricular, arcuate, and other hypothalamic nuclei and the pituitary gland and in the plasma release of ACTH following noxious stimulation or EA treatment. However, c-fos activation provoked by immobilization stress though markedly decreased was not abolished by capsaicin, whereas plasma release of ACTH remained undiminished (Pan et al., 1997). These findings suggest that EA acts on the hypothalamic pituitary corticotropic axis through an exclusively physical effect depending on the noxious signal elicited in the somatosensory pathway.
Neural mechanism underlying acupuncture analgesia
2008, Progress in NeurobiologyCitation Excerpt :In deeply anaesthetized rats, EA enhanced ATCH plasma release and up-regulated expression of Fos in the hypothalamic–pituitary corticotrope axis without usual autonomic responses to psychological stress, such as tachycardia or blood pressure elevation, which was blocked by deprivation of nociceptive primary afferent input using neonatal capsaicin. ( Pan et al., 1996, 1997). In the awaking rat, immobilization stress predominantly is a psychological stressor.
- 1
On leave from the Institute of Acupuncture, China Academy of Traditional Chinese Medicine, Beijing, China