Organization of exteroceptive inputs onto nonspiking local interneurones in the crayfish terminal abdominal ganglion

✍ Scribed by Nagayama, Toshiki

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 373 KB
• Volume: 279
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/(sici)1097-010x(19970901)279:1<29::aid-jez3>3.0.co;2-3

✦ Synopsis

Uropod movements of the crayfish, Procambarus clarkii (Girard) are controlled by nonspiking local interneurones as well as by spiking local interneurones and ascending interneurones in the terminal abdominal ganglion. The organization of synaptic connections among these local circuit neurones was examined.

Particular nonspiking interneurones received direct excitatory input from a number of mechanosensory afferents. Afferent spikes consistently elicited depolarizing postsynaptic potentials in the nonspiking interneurones with a central delay time of 1.0-1.3 msec. The latency of the depolarizing PSPs in other nonspiking interneurones was, by contrast, too long to be considered as a direct connection. This delayed excitatory input was mediated by identified ascending interneurones that received direct inputs from the afferents and made direct output connections with the nonspiking interneurones. Spikes of ascending interneurones were consistently followed by depolarizing PSPs in the nonspiking interneurones with a latency of 0.6-1.1 msec. A direct inhibitory input from the mechanosensory afferents to the nonspiking interneurones was not found, although an inhibitory input was mediated by identified spiking local interneurones that also received direct inputs from the afferents. The hyperpolarizing PSPs followed the spikes of the spiking local interneurones with a latency of 0.5-0.6 msec.

Ascending interneurones always had direct excitatory outputs while spiking local interneurones had inhibitory outputs to nonspiking interneurones, so that there was a directional flow of information. The connections between spiking interneurones and nonspiking interneurones were not reciprocal but one-way.