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Comments on Hapiak, V. et al. (2013) International Worm Meeting "Monoamines amplify and focus global peptidergic signaling cascades to modulate nociceptive responses in Caenorhabditis elegans." (0)
Overview
Hapiak, V., Stein, A., Law, W.J., Ortega, A., & Komuniecki, R.W. (2013). Monoamines amplify and focus global peptidergic signaling cascades to modulate nociceptive responses in Caenorhabditis elegans presented in International Worm Meeting. Unpublished information; cite only with author permission.
Most key behaviors in C. elegans are modulated by monoamines through 14 distinct monoamine receptors, many with clear homologues in vertebrates. For example, aversive responses mediated by the two nociceptive ASH sensory neurons are inhibited by both tyramine (TA) and octopamine (OA) that appear to function similarly to epinephrine and norepinephrine in vertebrates. The present study demonstrates that the TA inhibition of food or serotonin-stimulated aversive responses to dilute 1-octanol requires the Gaq-coupled TA receptor, TYRA-3 and the activation of a global "inhibitory" signaling cascade involving a complex mix of additional monoamines, including OA and dopamine, and neuropeptides. Importantly, the neuropeptides released from the ASI sensory neurons required for either tyraminergic or octopaminergic inhibition of aversive responses are distinct, suggesting that individual monoamines can stimulate the release of different subsets of ASI neuropeptides. Together, these studies highlight the complexity of TA inhibition, with TA activating a widespread signaling cascade, and suggest that signaling from a complex "humoral soup" of monoamines is amplified and focused by the localized synaptic (perisynaptic) release of neuropeptides to define nutritional status in the modulation of a range of sensory-mediated behaviors. In addition, they suggest that the TA and OA inhibition of aversive responses in C. elegans parallels the noradrenergic modulation of pain in mammals where noradrenergic inhibition also activates global, inhibitory, peptidergic signaling cascades. These studies are continuing to define the relationship between monoaminergic and peptidergic signaling in the modulation of sensory-mediated locomotory decision-making. These studies were supported by NIH Grant AI072644 to RWK.
Affiliations:
- Department of Biology, Brandeis University, Waltham, MA
- Department of Biological Sciences, University of Toledo, Toledo, OH