The cord dorsum potential evoked by stimulation in the ventrolateral aspect of periaqueductal grey (PAG-CDP) was recorded from the dorsal surface of the spinal lumbosacral cord in rats. PAG stimulation with the same parameters as for producing PAG-CDP inhibited the C discharges of convergent neurons in spinal dorsal horn. There was a positive correlation between the time course of the inhibitory effect of PAG on convergent neurons and the duration of the slow wave of PAG-CDP. a positive correlation also pre...