The Effect of DOPA on the Spinal Cord 4. Depolarization Evoked in the Central Terminals of Contralateral Ia Afferent Terminals by Volleys in the Flexor Reflex Aflerents

JANKOWSKA, E., S. LUND and A. LUNDBERG. The effect of DOPA on the spinal cord. 4. Depolarization evoked in the central terminals of contralateral Ia afferent terminals by volleys in the jlexor rejlex afferents. Acta physiol. scand. 1966. 68. 337-341. After injection of DOPA in unanaesthetized spinal cats volleys in the flexor reflex afferents (FRA) evoke a late long lasting contralateral dorsal root potential. Measurements of excitability of contralateral afferent terminals show a corresponding depolarization of Ia, but not of Ib or cutaneous afferent terminals. Results are also presented showing that transmission from the FRA to contralateral Ia afferent terminals can be inhibited from the FRA. In previous papers in this series it has been shown that after an i.v. injection of 1-3,4-dihydroxyphenylalanine (DOPA) volleys in the flexor reflex afferents evoke a late ipsilateral dorsal root potential (DRP) which is caused by a selective depolarization in the central terminals of Ia afferents (Andtn et al. 1966a, b). In the present paper it will be shown that after DOPA volleys in the FRA produce similar effects on the contralateral side. The experimental procedures have been given in the previous papers.

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