Cockroaches, synaptic transmission

Proctolin appears to potentiate synaptic transmission in the central nervous system of the cockroach P. americana (37). Bursts of spike activity in the ventral nerve cord of this insect were elicited by mechanical stimulation of the cereal organs. In the presence of micromolar proctolin, the peak frequency and the duration of bursts were slowly, but significantly, increased. Carbacol, by comparison, caused an immediate enhancement of spontaneous activity, but potentiation of bursts was not observed. Thus, it was concluded that proctolin might function as a neuromodulator in the terminal ganglion. 

Yamasaki, T., and Naraha.shi, T, (I960), Synaptic transmission in the last abdominal ganglion of the cockroach. J. In.seci Physiol. 4, 1-13,... 

Proctolin, H-Arg-Tyr-Leu-Pro-Thr-OH, a bioactive neuropeptide modulating in-terneuronal and neuromuscular synaptic transmissions in a wide variety of arthropods. It was discovered as an excitatory neurotransmitter from the intestinal musculature of insects. Extremely low concentrations (10 mol L ) cause violent contraction of the end of the gut. For the first isolation of proctolin, 125,000 cockroaches (Periplaneta americana) were required. Although proctolin was the first insect neuropeptide to be discovered, it is now regarded as the main neuromuscular trans-mitter/modulator in the gut of most insect species. In 2003, a G protein-coupled receptor for proctolin in Drosophila mdanogaster was identified and characterized [A. N. Star-ratt, B. E. Brown, Life Sci. 1975, 17, 1253 D. Konopihska, G. Rozihski, J. Peptide Sci. 1999, 5, 533 E. J. Johnson et al., Proc. Natl. Acad. Sci. USA 2003, 100, 6198]. 

The function of a synapse is to stop transmission and normally there are many presynaptic impulses before one postsynaptic impulse is set up. Thus if there are 20 presynaptic action potentials setting up one postsynaptic action potential, the synaptic ratio would be 20 1. In the cockroach, if the ChE decreased, the efficacy of the... 

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