Insect mechano-sensory system: Development of biochemical and electrophysiological properties in absence of external activation

Abstract

1. Following amputation of, or application of 0.125–0.5 mol/1 CoCl2 to a cercus (hind sensory appendage) of a cricket degeneration of sensory neurons occurs within 48 h. 2. Degeneration is manifested by (i) abolition of receptor potentials, cessation of both (ii) ongoing spiking activity, and (iii) synaptic transmission, and (iv) a 95% drop in choline acetyltransferase activity, as measured from the cereal nerve. 3. Following degeneration, in larval stages, differentiation of new cerci takes place. This de novo regeneration is seen in a gradual increase of (i) choline acetyltransferase activity, (ii) receptor potential amplitudes and (iii) development of synaptic transmission. 4. Depending on the stage of development and the method used to induce degeneration, larvae develop into adults either with or without external cuticular hairs. Cereal sensilla lacking these hairs cannot transduce external stimuli. Absence of sensory activation by external stimuli does not prevent differentiation of cereal sensory neurons including the formation of functional synaptic connections. 5. Regenerating cereal systems, including those devoid of sensory activation, develop at a faster rate than their normal contralateral counterparts up to adulthood. 6. During adulthood choline acetyltransferase activity continues to increase in cereal nerves of normal and regenerating cerci at similar rates. This increase is seen also in cerci regenerating without sensory activation.