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A recurrent collateral pathway for presynaptic inhibition in the rat cuneate nucleus

1972; Elsevier BV; Volume: 44; Issue: 1 Linguagem: Inglês

10.1016/0006-8993(72)90366-6

1872-6240

Neil C. Davidson, Carol A. Smith,

Pain Mechanisms and Treatments

Stimulation of the ipsilateral forelimb, the contralateral forelimb and the contralateral medial lemniscus produced long-lasting inhibition of cuneothalamic relay (CTR) cells, primary afferent depolarization (PAD) and interneurone activity in the cuneate nucleus of the chloralose-urethane anaesthetized rat. Lemniscal stimulation was controleed by monitoring of sensorimotor cortical responses and histological identification of stimulus sites from which minimal threshold reponses could be evoked. With low stimulus strengths there was no evidence of current spread to the underlying corticospinal tract. Two groups of cuneate interneurones were of special interest. Group A was activated both by stimulation of the ipsilateral forelimb and the contralateral medial lemniscus. Group B was activated by ipsilateral and contralateral forelimb stimulation and by stimulation of the contralateral medial lemniscus. It is concluded that a recurrent collateral pathway from the medial lemniscus, involving successively A- and B-type interneurones, forms a possible central pathway for the production of presynaptic inhibition and the associated PAD in the rat cuneate nucleus. It is also concluded that interneurone B provides a common path for the contralateral pathway producing these effects in the cuneate nucleus.