Developmental changes and acetylcholinesterase activity in the metamorphosing brain of Tenebrio molitor: Correlation to ecdysteroid titers

Abstract

The brain of Tenebrio molitor exhibited marked fluctuations in acetylcholinesterase (AChE) activity throughout metamorphosis. This was true AChE activity, since it was inhibited by high substrate concentrations and by 10 pM of the specific AChE inhibitor BW284C51 [(I ,5-bis'4-allyldimethylammoniumphenyl)-pentan-3-one dibromide] but not by iso-OMPA (tetraisopropylpyrophosphoramide), a cholinesterase (but not AChE) inhibitor. The histochemical AChE activity was localized in the neuropile and the nuclear envelope of neurons and glial cells. The enzyme extracted from brains with 1 O h Triton X-I 00 and 1 M NaCl sedimented as a single peak in a sucrose density gradient, with a sedimentation coefficient of 5.4s. This single AChE sedimentation peak was mainly due to an amphiphilic dimeric form. AChE activity per brain increased in newly ecdysed pupa. AChE activity per milligram of protein exhibited a peak in the mid-pupa which could be correlated to the increase in ecdysteroid titers. o 1994 WiIey-Liss, Inc.