Bosco R, Eblen-Zajjur A

Language: Spanish
References: 42
Page: 155-161
PDF size: 124.57 Kb.

ABSTRACT

The nociceptive sensorial signals that enter the dorsal spinal horn (DH) through primary afferents, establish synaptic connections with neuronal circuits of itself, to which descendent supraspinal modulators pathways and/or propriospinals pathways converge too, exerting a powerful inhibiting or excitatory modulation of the nociceptive experience. Objective: to evaluate and characterize mathematically the postdischarge periods of the lumbar evoked potentials (LEP) of the DH in rats. Materials and methods: the experiments were done in male Sprague-Dawley rats; an electrical paired transcutaneal stimulus (20V; 0,2Hz; interstimulus latency of 1- 200ms) was applied. Five pairs of LEP by each interestimulus interval were registered and stored; the N and P waves generated by the second conditioner stimulus (Nc and Pc) were averaged. Results: for interstimulus latencies ‹7.5 ms the inhibition of the Nc and Pc waves was absolute. The Nc wave showed a postdischarge inhibition period of 28ms and a supernormal period (110%) between 28-80ms of latency. The P wave maintained a constant increase of amplitude from 9.5ms without supernormal period. The relation between the interstimulus latency and the amplitude of the N and P waves is of polinomial character but with very different coefficients. Conclusions: the results suggest that excitatory and inhibitory postdischarge afferent periods in the DH surpass in duration the ones reported for fibers and individual neurons, bringing additional evidence about the behavior of proprio and supraspinal neuronal circuits of afferent modulation at the DH.

REFERENCES

1. Le Bars D, Dickenson AH, Besson JM, Villanueva L. Aspects of sensory processing through convergent neurons, In Yaksh TL, ed. Spinal afferent processing. New York. Plenum 1986; 467-504.

2. Besson JM, Chaouch A. Peripheral and spinal mechanisms of nociception. Physiol Rev 1987; 6: 67-186.

3. Sandkühler J, Chen JG, Cheng G, Randic M. Low-frequency stimulation of afferent Aδ-fibers induces long-term depression at primary afferent synapses with substantia gelatinosa neurons in the rat. J Neurosci 1997; 17: 6483-91.

4. Lu Y, Perl ER. Modular organization of excitatory circuits between neurons of the spinal superficial dorsal horn (laminae I and II). J Neurosci 2005; 25: 3900-7.

5. Streit J, Tscherter A, Darbon P. Rhythm generation in spinal cultures: is it the neuron or the network?. In Taketani M, Baudry M, eds. Advances in network electrophysiology using multielectrode arrays. New York. Springer 2005; (in press).

6. Ren K, Dubner R. Descending modulation in persistent pain: an update. Pain 2002;100:1-6.

7. Villanueva L. Asta dorsal medular: ¿cuál es su rol en el procesamiento de los impulsos que generan la sensación dolorosa?. Rev Soc Esp Dolor 1998; 5: 52-69.

8. Vikman KS, Kristensson K, Hill RH. Sensitization of dorsal horn neurons in a two-compartment cell culture model: wind-up and long-term potentiation-like responses. J Neurosci 2001;21:1-6.

9. Nakatsuka T, Chen M, Takeda D, King C, Ling J, Xing H, et al. Substance P-driven feed-forward inhibitory activity in the mammalian spinal cord. Mol Pain 2005; 29;1-20.

10. Lu Y, Peri ER. A specific inhibitory pathway between substantia gelatinosa neurons receiving direct C-fiber input. J Neurosci 2003; 23: 8752-8.

11. Jankowska E. Spinal interneuronal systems: identification, multifunctional character and reconfigurations in mammals. J Physiol 2001; 15: 31-40.

12. Lin TB. Tetanization-induced pelvic-to-pudendal reflex plasticity in anesthetized rats. Am J Physiol Renal Physiol 2004; 287: 245-51.

13. Shimoji K. Origins and properties of spinal cord evoked potentials. In Dimitrijevié MR, Halter JA, eds. Atlas of human spinal cord evoked potentials. Washington: Butterworth-Heinemann 1995; 1-25.

14. Galik J, Conway C. Evoked potentials: principles and techniques. In Patterson M, ed. California. Kopf D lnstruments 1997.

15. National Institute of Health (NIH). Guide for the care and use of laboratory animals. Washington (DC). National Academy Press; 1996.

16. Tanaka H, Ono K, Shibasaki H, Isa T, Ikenaka K. Conduction properties of identified neural pathways in the central nervous system of mice in vivo. Neurosci Res 2004; 49: 113-22.

17. Cardinali D. Los componentes del sistema nervioso. Generación y conducción de potenciales en el sistema nervioso. In Tresguerres JAF, ed. Fisiología humana. Madrid: McGraw Hill Interamericana; 1999; 57-8.

18. Eblen-Zajjur A, Sandkühler J. Synchronicity of nociceptive and non-nociceptive adjacent neurons in the spinal dorsal horn of the rat: stimulus-induced plasticity. Neuroscience 1997;76:39-54.

19. Willis WD, Coggeshall RE. Sensory mechanisms of the spinal cord. New York: Plenum Press; 2004.

20. Sandkühler J, Eblen-Zajjur A, Fu Q-G, Forster C. Differential effect of spinalization on the discharges of simultaneously recorded nociceptive and non-nociceptive spinal dorsal horn neurons. Pain 1995; 60: 55-65.

21. Earle KM. The tract of Lissauer and its possible relation to the pain pathway. J Comp Neurol 1952; 96: 93-109.

22. Pearson AA. Role of gelatinous substance of spinal cord in conduction of pain. Arch Neurol Psychiatry 1952; 68: 515-29.

23. Réthelyi M, Szentágothai J. The large synaptic complexes of the substantia gelatinosa. Exp Brain Res 1969; 7: 258-74.

24. Grudt TJ, Perl ER. Correlations between neuronal morphology and electrophysiological features in the rodent superficial dorsal horn. J Physiol (Lond) 2002; 540: 189-207.

25. Adrian ED, Lucas K. On the summation of propagated disturbances in nerve and muscle. J Physiol 1912; 44: 68-124.

26. Caputo C, Jaffe E. Transmisión sináptica. In Tresguerres JAF, ed. Fisiología humana. Madrid: McGraw Hill Interamericana; 2005.

27. Stockbridge N. Etiology of the supernormal period. Biophys 1988; 54: 777-80.

28. Collins JG. A descriptive study of spinal dorsal horn neurons in the physiologically intact, awake, drug-free cat. Brain Res 1987; 416: 34-42.

29. Latham PE, Richmond BJ, Nelson PG, Nirenberg S. Intrinsic dynamics in neuronal networks. I. Theory. J Neurophysiol 2000; 83: 808-27.

30. Yoshimura M, Jessell T. Amino acid-mediated EPSPs at primary afferent synapses with substantia gelatinosa neurones in the rat spinal cord. J Physiol 1990; 430: 315-35.

31. Schouenborg J. Functional and topographical properties of field potentials evoked in rat dorsal horn by cutaneous C-fibre stimulation. J Physiol 1984; 356: 169-92.

32. Basbaum Al, Fields HL. Endogenous pain control mechanism: review and hypothesis. Ann Neurol 1978; 4: 451-62.

33. Vanegas H, Barbaro NM, Fields HL. Tail-flick related activity in medullospinal neurons. Brain Res 1984a; 321: 135-41.

34. Vanegas H, Barbaro NM, Fields HL. Midbrain stimulation inhibits tail-flick only at currents sufficient to excite rostral medullary neurons. Brain Res 1984b; 321: 127-33.

35. Cross SA. Pathophysiology of pain. Mayo Clin Proc 1994; 69: 375-83.

36. Vanegas H, Schaible HG. Descending control of persistent pain: inhibitory or facilitatory?. Brain Res Rev 2004;46:295-309.

37. Serrano-Atero MS, Páramo F, Cañas A, García-Saura P, SerranoÁlvarez C, Caballero J. Modulación descendente de la información nociceptiva (I). Rev Soc Esp Dolor 2002; 9: 382-90.

38. Kim KW, Cox BM. Inhibition of norepinefrine release from rat cortex slices by opioids: differences among agonist in sensitivities to antagonist suggest receptor heterogeneity. J Pharmacol Exp Ther 1993; 267: 1153-60.

39. Schoffelmeer ANM, DeVries TJ, Hogenboom F, Mulder AH. Mu and delta receptor inhibitorily linked to dopamine-sensitive adenilate cyclase in rat striatum display a selectivity profile toward endogenous opioid peptides different from that of presinaptic mu, delta and kappa receptors. J Pharmacol Exp Ther 1993; 267: 205-10.

40. Zemian FP, Murphy AZ, Behbehani MM. 5-HT1A receptors mediate the effect of the bulbospinal serotonin system on spinal dorsal horn nociceptive neurons. Pharmacol 1994;48:1-10.

41. Fields HL, Basbaum Al. Central nervous system mechanism of pain modulation. In Wall PD, Melzack R, eds. Textbook of pain. Londres: Chruchill Livingstone; 1999; 309-29.

42. Millan MJ. Descending control of pain. Prog Neurobiol 2002; 66: 355-474.