Nitric oxide modulates a swimmeret beating rhythm in the crayfish

Area of Science:

• Neuroscience
• Marine Biology
• Cell Signaling

Background:

• Swimmerets in crayfish are crucial for locomotion, posture, and reproduction.
• Swimmeret motor neurons typically exhibit silent or low-frequency activity.
• Cholinergic stimulation can induce rhythmic motor neuron firing.

Purpose of the Study:

• To investigate the modulatory roles of nitric oxide (NO) and cyclic AMP (cAMP) on crayfish swimmeret motor neuron activity.
• To elucidate the signaling pathways involved in regulating rhythmic swimmeret beating.

Main Methods:

• Isolated crayfish abdominal nerve cord preparations were used.
• Pharmacological agents including cholinergic agonists, NO donors/inhibitors, and cyclic nucleotide analogs were applied.
• Effects on motor neuron spike frequency and bursting activity were measured.

Main Results:

• Nitric oxide (NO) application, via L-arginine or SNAP, increased carbachol-induced rhythmic bursting frequency.
• Inhibition of NO synthesis (L-NAME) or soluble guanylate cyclase (ODQ) reduced bursting frequency.
• Cyclic AMP (cAMP) analogs induced rhythmic bursting, and this was enhanced by L-arginine.
• Adenylate cyclase inhibition (SQ22536) abolished carbachol-induced rhythmic activity.

Conclusions:

• NO acts as a neuromodulator, facilitating swimmeret motor neuron activity through a NO-cGMP-dependent pathway.
• A cAMP signaling system is essential for generating rhythmic motor neuron bursts.
• The NO-cGMP pathway enhances cAMP activity, thereby facilitating rhythmic swimmeret beating.