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Journal of Experimental Biology 37,513-533 (1960)
Published by Company of Biologists 1960

The Nutrition of the Central Nervous System in the Cockroach Periplaneta Americana L : The Exchange and Metabolism of Sugars

J. E. TREHERNE ¹

¹ A.R.C. Unit of Insect Physiology, Department of Zoology, University of Cambridge

1. ¹⁴C-labelled glucose injected into the cockroach was found to be rapidly converted to trehalose, only small amounts remaining in equilibrium with the disaccharide in the haemolymph. The entry of these sugars into the cockroach central nervous system was studied by following the increase in radioactivity within the abdominal nerve cord after the injection of radioactive glucose into the haemolymph.

2. The levels of radioactivity increased at closely similar rates in different parts of the abdominal nerve cord.

3. The influx of sugars into the nerve cord was calculated to be equivalent to 1.09 mM. glucose/l. of nerve cord water/min.

4. The greater part of the ¹⁴C entering the nerve cord originated from the trehalose, only about 7% being derived from the small amount of glucose in the haemolymph. The movement of the relatively small number of glucose molecules into the nerve cord occurred, nevertheless, at approximately 2.5 times the rate of the larger trehalose molecules.

5. Chromatographic analysis revealed that more than half of the absorbed ¹⁴C was incorporated as glutamic acid and glutamine in the nerve cord. Smaller amounts of glycogen, trehalose, glucose, aspartic acid and occasional traces of alanine were found. In the isolated nerve cord substantial amounts of alanine accumulated, the formation of the other amino acids being reduced. ¹⁴CO₂ production in vitro was found, after 1 hr., to represent only about 1% of the total activity within the nerve cord.

6. The results demonstrate a linkage of carbohydrate and amino acid metabolism and represent circumstantial evidence for the presence of the tricarboxylic acid cycle enzymes in the central nervous system of this insect.