Comparative studies of purinergic nerves

Area of Science:

• Neuroscience
• Gastroenterology
• Comparative Physiology

Background:

• Purinergic nerves are widespread in the gastrointestinal tract of vertebrates.
• These nerves, originating in Auerbach's plexus, innervate the circular muscle coat and influence digestive processes.
• They are implicated in key functions such as receptive relaxation of the stomach and modulation of peristalsis.

Purpose of the Study:

• To investigate the role and characteristics of purinergic nerves in the gastrointestinal tract.
• To identify the neurotransmitter released by these nerves.
• To explore the potential evolutionary significance of purinergic innervation.

Main Methods:

• Electrophysiological recordings of smooth muscle cell responses to nerve stimulation.
• Pharmacological characterization using specific blocking agents and agonists.
• Analysis of nerve terminal morphology, focusing on vesicle types.
• Biochemical assays to identify enzymes involved in neurotransmitter metabolism.

Main Results:

• Purinergic nerve stimulation elicits inhibitory junction potentials (IJPs) in smooth muscle, abolished by tetrodotoxin but not atropine or adrenergic blockers.
• Adenosine triphosphate (ATP) was identified as the primary neurotransmitter, evidenced by its synthesis, release, and ability to mimic nerve-induced responses.
• Specific enzymes for ATP inactivation (Mg-activated ATPase, 5'-nucleotidase, adenosine deaminase) were found.
• Certain drugs demonstrated similar effects on both exogenous ATP and nerve stimulation responses.

Conclusions:

• Purinergic nerves play a crucial role in gastrointestinal motility regulation through ATP release.
• The distinct vesicle population and pharmacological profile support ATP as the neurotransmitter.
• Purinergic nerves may represent an ancient component of the vertebrate nervous system.