Abstract
The ecdysis behavioral sequence in insects is a classic fixed action pattern (FAP) initiated by hormonal signaling. Ecdysis triggering hormones (ETHs) release the FAP through direct actions on the CNS. Here we present evidence implicating two groups of central ETH receptor (ETHR) neurons in scheduling the first two steps of the FAP: kinin (aka drosokinin, leucokinin) neurons regulate pre-ecdysis behavior and CAMB neurons (CCAP, AstCC, MIP, and Bursicon) initiate the switch to ecdysis behavior. Ablation of kinin neurons or altering levels of ETH receptor (ETHR) expression in these neurons modifies timing and intensity of pre-ecdysis behavior. Cell ablation or ETHR knockdown in CAMB neurons delays the switch to ecdysis, whereas overexpression of ETHR or expression of pertussis toxin in these neurons accelerates timing of the switch. Calcium dynamics in kinin neurons are temporally aligned with pre-ecdysis behavior, whereas activity of CAMB neurons coincides with the switch from pre-ecdysis to ecdysis behavior. Activation of CCAP or CAMB neurons through temperature-sensitive TRPM8 gating is sufficient to trigger ecdysis behavior. Our findings demonstrate that kinin and CAMB neurons are direct targets of ETH and play critical roles in scheduling successive behavioral steps in the ecdysis FAP. Moreover, temporal organization of the FAP is likely a function of ETH receptor density in target neurons.
Highlights
Innate behaviors are stereotypic patterns of movement inherited from birth that require no prior experience for proper execution
We assessed functional consequences of ablating three central peptidergic ecdysis triggering hormones (ETH) receptor (ETHR) ensembles defined by peptides they release (FMRFa, eclosion hormone, and crustacean cardioactive peptide (CCAP)) on the ecdysis fixed action pattern (FAP)
Loss of FMRFa neurons had no effect on scheduling of the FAP, whereas loss of eclosion hormone neurons had a minor effect, producing a ~6 min delay in the switch from pre-ecdysis to ecdysis behavior
Summary
Innate behaviors are stereotypic patterns of movement inherited from birth that require no prior experience for proper execution. Among such behaviors are fixed action patterns that, once initiated, run to completion independent of sensory inputs. Ecdysis represents a “chemically-coded” behavioral sequence triggered by peptidergic ecdysis triggering hormones (ETH), which orchestrate a downstream peptidergic cascade leading to sequential activation of central pattern generators underlying patterned motor activity [2,3]. The term FAP has fallen into disuse, since innate behaviors generally exhibit considerable plasticity. The invariant nature of the ecdysis behavioral sequence makes it a clear example a classic FAP. In depth analysis of ecdysis behavior may provide a more thorough understanding of how hormones assemble and regulate behavioral circuitry in the brain, in particular circuits that operate sequentially
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
