Projection neurons with shared cotransmitters elicit different motor patterns from the same neural circuit.

Area of Science:

• Neuroscience
• Neurophysiology
• Computational Neuroscience

Background:

• Neuronal specificity is often linked to unique cotransmitter combinations.
• The stomatogastric nervous system (STG) in Cancer borealis provides a model for studying neural circuit modulation.
• Projection neurons like modulatory proctolin neuron (MPN) and modulatory commissural neuron 1 (MCN1) influence STG rhythms.

Purpose of the Study:

• To investigate the role of Cancer borealis tachykinin-related peptide Ia (CabTRP Ia) in differentiating the functions of MCN1 and MPN.
• To test the hypothesis that distinct cotransmitter complements confer neuronal specificity.

Main Methods:

• Selective activation of projection neurons MPN and MCN1 in the crab STG.
• Pharmacological blockade of tachykinin receptors using Spantide I to assess the contribution of CabTRP Ia.
• Analysis of resulting rhythmic outputs (gastric mill and pyloric rhythms).

Main Results:

• MCN1 activation elicits both gastric mill and pyloric rhythms, while MPN elicits only a pyloric rhythm.
• Blocking CabTRP Ia action with Spantide I abolished the gastric mill rhythm elicited by MCN1.
• The pyloric rhythm elicited by MCN1, even without CabTRP Ia, remained distinct from the MPN-elicited pyloric rhythm.

Conclusions:

• CabTRP Ia partially accounts for the distinct neural outputs of MCN1 and MPN.
• Projection neurons may employ diverse strategies, including differential use of cotransmitters, to generate distinct network outputs.
• This supports the hypothesis that neuronal specificity arises from a combination of factors, not solely distinct cotransmitter sets.