Wednesday, June 13, 2007

Drooling cockroaches

Ok, I guess the correct title should have been salivating cockroaches, but that doesn't sounds as cool - and anyway, the best title was already used by PLOS One: Pavlov's Cockroach by Hidehiro Watanabe and Makoto Mizunami

The two Japanese scientists have studied the salivation of cockroaches, and how those could be activated by specific odors, that the cockroaches associated with food. This study is of course very similar to Pavlov's classic study of a similar mechanism in dogs (used sounds instead of odors).

The interesting part of this study, is that the mechanisms behind the salivation is little understod, and had so far only been observed in Humans and dogs.

Secretion of saliva to aid swallowing and digestion is an important physiological function found in many vertebrates and invertebrates. Pavlov reported classical conditioning of salivation in dogs a century ago. Conditioning of salivation, however, has been so far reported only in dogs and humans, and its underlying neural mechanisms remain elusive because of the complexity of the mammalian brain. We previously reported that, in cockroaches Periplaneta americana, salivary neurons that control salivation exhibited increased responses to an odor after conditioning trials in which the odor was paired with sucrose solution. However, no direct evidence of conditioning of salivation was obtained. In this study, we investigated the effects of conditioning trials on the level of salivation. Untrained cockroaches exhibited salivary responses to sucrose solution applied to the mouth but not to peppermint or vanilla odor applied to an antenna. After differential conditioning trials in which an odor was paired with sucrose solution and another odor was presented without pairing with sucrose solution, sucrose-associated odor induced an increase in the level of salivation, but the odor presented alone did not. The conditioning effect lasted for one day after conditioning trials. This study demonstrates, for the first time, classical conditioning of salivation in species other than dogs and humans, thereby providing the first evidence of sophisticated neural control of autonomic function in insects. The results provide a useful model system for studying cellular basis of conditioning of salivation in the simpler nervous system of insects.

Quite interesting, and hopefully something that will give us a better understand of how brains work.

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