Previous results had shown that in the cat subliminal electrical stimulation of the thalamic ventrolateral nucleus (VL) reduces the amplitude of the evoked potentials elicited in the homonymous contralateral nucleus upon somatic peripheral stimulation ("transversal inhibition"), and that the reduction is stronger when muscular rather than cutaneous nerves are activated. In view of the fact that VL responses to both muscular and cutaneous afferents are known to be due to Group II and Group III fibers, the present experiments were aimed at ascertaining, by means of electroneurographic analysis and graded stimulation, which afferent fiber group brings about in the VL nucleus the response component most sensitive to transversal inhibition. According to the results obtained, the strongest inhibitory effect was seen on the responses evoked by activation of Group II fibers, particularly of muscular origin. The effect on the VL responses to Group III afferents was very scarce, independently of their peripheral origin. Intermediate degrees of inhibition were observed when both groups of fibers were simultaneously activated. The interaction curves obtained for the different activation channels are briefly discussed.
Referenze Bibliografiche
[1] H. SAKATA, T. ISHIJIMA e Y. TOYODA, «Jap. J. Physiol.», 16, 42 (1966).
[2] T. DESIRAJU e D. P. PURPURA, «Brain Research», 15, 544 (1969).
[3] J. MASSION, P. ANGAUT e D. ALBE-FESSARD, «Electroenceph. din. Neurophysiol.», 19, 433 (1965).
[4] A. BAVA, F. CICIRATA, T. MANZONI e M. MARICCHIOLO, «Rend. Accad. Naz. Lincei», Classe Sci. fis., mat. nat., Serie VIII, 48, 705 (1970).
[5] D. P. C. LLOYD, Spinal mechanisms involved in somatic activities, in J. Field, H. W. Magoun e V. E. Hall, «Neurophysiology», Vol. II. Handbook of Physiology, Section I, 929-949. «Am. Physiol. Soc.», Washington, D. C. (1960).
[6] H. H. JASPER e C. AJMONE-MARSAN, A stereotaxic atlas of the diencephalon of the Cat. Ottawa, The National Research Council of Canada (1954).
[7] O. POMPEIANO e J. E. SWETT, «Arch. ital. Biol.», 101, 552 (1963).
[8] A. MALLART, «J. Physiol., London», 194, 337 (1968).
[9] S. A. ANDERSSON, S. LANDGREN e D. WOLSK, «J. Physiol., London», 183, 576 (1966).
[10] R. M. ECCLES e A. LUNDBERG, «Arch. ital. Biol.», 97, 199 (1959).
[11] B. HOLMQVIST e A. LUNDBERG, «Acta physiol, scand.», 54, Suppl. 186 (1961).
[12] S. GRILLNER, «Acta physiol, scand.», 77, Suppl. 327 (1969).
[13] K. SASAKI e T. TANAKA, «Jap. J. Physiol.», 13, 64 (1963).
[14] N. A. BUCHWALD e C. D. HULL, «Brain Research», 6, 1 (1967).
[15] R. TARNECKI e J. KONORSKI, «Acta Biol. Exp.», 29, 1 (1969).
[16] J. STERN e A. A. WARD, «Arch. Neurol.», 3, 193 (1960).
[17] N. YANAGISAWA, H. NARABAYASHI e H. SHIMAZU, «Arch. Neurol.», 9, 348 (1963).
[18] R. HASSLER, Thalamic regulation of muscle tone and the speed of movements, in D. P. Purpura e M. D. Yahr, «The Thalamus», 419-438, Columbia University, New York (1966).
Con il contributo del Ministero per i Beni e le Attività Culturali