Central control of the sensory afferent terminals from a leg chordotonal organ in crayfish in vitro preparation.

In an in vitro preparation of the crayfish thoracic locomotor system, intracellular recordings have been performed from terminals of a leg joint coxo-basipodite chordotonal organ (CB). In the terminals, some depolarizing events are observed which display all the characteristics of the primary afferent depolarizations (PADs). PADs reduce the amplitude of orthodromic sensory spikes, and thus correspond to a presynaptic inhibition. PADs are tonic in a tonic preparation, and phasic (phase locked) in a rhythmic preparation. A control of the incoming information from the CB could thus be performed by the central nervous system during fictive locomotion.