Studies on the opioid mechanism in Tetrahymena

The effect of opioids and their antagonists on the nocifensive response of Caenorhabditis elegans to noxious thermal stimuli

Opiates modulate nociception in vertebrates. This has also been demonstrated in a number of invertebrate models. Herein, the effect of the opiate morphine and opioid neuropeptides Endomorphin 1 and 2 on the thermal avoidance (Tav) behavior of Caenorhabditis elegans is explored. Adult wild-type C. elegans N2 were collected from NGM plates using M9 buffer and exposed to morphine and endomorphine 1 and 2 in concentrations between 10(-8) and 10(-4) M (2.5 pmol/mg to 25 nmol/mg) for 30 min and tested for Tav. The opioid receptor antagonists Naloxone and CTOP were tested in combination with the drugs. Forty-seven percentage of the morphine exposed worms exhibited a class I response versus 76% of the control group (P < 0.001). Endomorphin 1 and 2 also caused a statistically significant reduction in class I responses, 36 and 39%, respectively. These effects were reversed with Naloxone and CTOP. Thermonocifensive behavior in C. elegans is modulated by opioids.

Analysis of expressed sequence tags (ESTs) in the ciliated protozoan Tetrahymena thermophila

To assess the utility of expressed sequence tag (EST) sequencing as a method of gene discovery in the ciliated protozoan Tetrahymena thermophila, we have sequenced either the 5' or 3' ends of 157 clones chosen at random from two cDNA libraries constructed from the mRNA of vegetatively growing cultures. Of 116 total non-redundant clones, 8.6% represented genes previously cloned in Tetrahymena. Fifty-two percent had significant identity to genes from other organisms represented in GenBank, of which 92% matched human proteins. Intriguing matches include an opioid-regulated protein, a glutamate-binding protein for an NMDA-receptor, and a stem-cell maintenance protein. Eleven-percent of the non-Tetrahymena specific matches were to genes present in humans and other mammals but not found in other model unicellular eukaryotes, including the completely sequenced Saccharomyces cerevisiae. Our data reinforce the fact that Tetrahymena is an excellent unicellular model system for studying many aspects of animal biology and is poised to become an important model system for genome-scale gene discovery and functional analysis.