Regulation of early embryonic behavior by nitric oxide in the pond snail Helisoma trivolvis
2002
SUMMARY Helisoma trivolvis embryos display a cilia-driven rotational
behavior that is regulated by a pair of serotonergic neurons named ENC1s. As
these cilio-excitatory motor neurons contain an apical dendrite ending in a
chemosensory dendritic knob at the embryonic surface, they probably function
as sensorimotor neurons. Given that nitric oxide (NO) is often associated with
sensory neurons in invertebrates, and has also been implicated in the control
of ciliary activity, we examined the expression of NO synthase (NOS) activity
and possible function of NO in regulating the rotational behavior in H.
trivolvis embryos. NADPH diaphorase histochemistry on stage E25-E30
embryos revealed NOS expression in the protonephridia, buccal mass,
dorsolateral ciliary cells and the sensory dendritic knobs of ENC1. At stages
E35-40, the pedal ciliary cells and ENC19s soma, apical dendrite and proximal
descending axon were also stained. In stage E25 embryos, optimal doses of the
NO donors SNAP and SNP increased the rate of embryonic rotation by twofold, in
contrast to the fourfold increase caused by 100 μmol l -1
serotonin. The NOS inhibitors L-NAME (10 mmol l -1 ) and 7-NI (100μ
mol l -1 ) decreased the rotation rate by approximately 50%,
whereas co-addition of L-NAME and SNAP caused a twofold increase. In an
analysis of the surge and inter-surge subcomponents of the rotational
behavior, the NO donors increased the inter-surge rotation rate and the surge
amplitude. In contrast, the NO inhibitors decreased the inter-surge rotation
rate and the frequency of surges. These data suggest that the embryonic
rotational behavior depends in part on the constitutive excitatory actions of
NO on ENC1 and ciliary cells.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
49
References
23
Citations
NaN
KQI