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.

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Neuronal generation had been thought to occur only during development; however, current research indicates that neurogenesis continues into adulthood in the hippocampus and olfactory regions. The model selected for study was the Ames Dwarf mouse, homozygous for the PROP‐1 gene mutation and deficient in pituitary hormones. Normal‐sized heterozygous litter mates were used as controls. The goal was to determine whether there were alterations in brain neurogenesis using the bromodeoxyuridine (BrdU) method to label dividing cells. 12‐month‐old male Dwarf and control mice (n=5–6/group) were injected IP for seven days with 50mg/kg of BrdU. Animals were perfused with paraformaldehyde, and consecutive 25 um sections were taken through the hippocampus. Immunofluorescence was used to localize BrdU and neuronal nuclear antigen, NeuN, a marker for mature neurons. There was no difference in the number of BrdU‐positive cells in Dwarf mice as compared to controls (13.5 ± 5.1 vs 12.6 ± 2.7). The percentage of co‐labeled BrdU and NeuN neurons showed a trend to be higher in Dwarf mice (69.9 ± 5.9% vs. 61.9 ± 12.6%; Dwarf vs control). Data indicate that there is an increase in proliferation of neural progenitor cells that can develop into mature neurons in the hippocampus of Ames Dwarf mice over controls. Supported by NIH R25GM086257 and Henry Jackson Foundation Subaward #686190.