Serotonin differentially modulates Ca2+ transients and depolarization in a C. elegans nociceptor

Area of Science:

• Neuroscience
• Molecular Biology
• Behavioral Science

Background:

• Monoamines and neuropeptides are key regulators of neuronal excitability and synaptic plasticity.
• In *C. elegans*, the ASH sensory neurons detect 1-octanol, triggering escape behaviors.

Purpose of the Study:

• To investigate the role of voltage-gated calcium channels (VGCCs) and intracellular calcium release in ASH neuron responses to 1-octanol.
• To examine the effect of serotonin on ASH neuron activity and calcium signaling during 1-octanol avoidance.

Main Methods:

• Electrophysiological recordings to measure ASH neuron depolarization.
• Calcium imaging to assess intracellular calcium transients in response to 1-octanol.
• Genetic and pharmacological manipulations of L-type VGCCs in *C. elegans*.

Main Results:

• 1-octanol induced significant increases in ASH calcium (Ca$^{2+}$), involving somatic L-type VGCCs and axonal L- and P/Q-type VGCCs, amplified by intracellular stores.
• Aversive responses to 1-octanol persisted despite reduced L-VGCC activity.
• Serotonin potentiated 1-octanol-evoked ASH depolarization but decreased somatic Ca$^{2+}$ transients.

Conclusions:

• ASH somal Ca$^{2+}$ transient amplitudes may not reliably predict neuronal depolarization or synaptic output.
• The relationship between Ca$^{2+}$ transient amplitude and neuronal activity is complex and not always straightforward.