Figure 8.—

Model for inhibition of egg laying until the uterus is filled with eggs. uv1 neurosecretory cells release tyramine and other neurotransmitters to inhibit egg-laying behavior until they are mechanically deformed by eggs in the uterus, and both heteromeric TRPV channels and the G-protein Gα_o are required in uv1 cells for this release. The relationship among mechanical deformation of uv1, TRPV activity, and Gα_o activity remains undetermined, leaving several possibilities consistent with the data. uv1 deformation could directly mechanically gate TRPV channels (arrow 1), affect Gα_o via a G-protein-coupled receptor (GPCR, arrow 2), or activation of both TRPV channels and Gα_o could be required in parallel. If mechanical deformation acts via the G protein, Gα_o could activate the TRPV channels to allow entry of Ca²⁺, a known activator of neurotransmitter vesicle release (arrows 3 and 5). Alternatively, if the TRPV channels are directly mechanically gated by uv1 deformation, a model that remains formally consistent with our analysis is that TRPV channels activate the G protein to in turn activate neurotransmitter release (arrows 4 and 6).