Developmental changes in the response of rat isolated duodenum to nicotine

Area of Science:

• Neurogastroenterology
• Developmental pharmacology
• Gastrointestinal physiology

Background:

• The gastrointestinal tract's response to stimuli changes significantly during development.
• Ganglionic stimulants like nicotine affect gut motility through various neural pathways.

Purpose of the Study:

• To investigate the developmental changes in the rat duodenum's response to nicotine and dimethylphenylpiperazinium.
• To elucidate the specific neurotransmitter systems involved in these responses at different life stages.

Main Methods:

• Isolated rat duodenum preparations from neonatal and adult rats.
• Recording of isotonic mechanical activity in response to ganglionic stimulants.
• Pharmacological blockade of specific neurotransmitter receptors and pathways (e.g., hexamethonium, tetrodotoxin, hyoscine, guanethidine).

Main Results:

• Neonatal duodenum exhibited contraction to nicotine/DMPP, blocked by cholinergic and neuronal inhibitors.
• Adult duodenum showed relaxation to nicotine/DMPP, blocked by neuronal inhibitors but not adrenergic/cholinergic ones.
• The shift from contraction to relaxation occurred around the third postnatal week.
• Nicotine-induced relaxation in adults involved peptidergic and purinergic (P1 and P2x purinoceptor) pathways.

Conclusions:

• The contractile response in neonatal rat duodenum is mediated by cholinergic transmission.
• The relaxant response in adult rat duodenum involves non-adrenergic, non-cholinergic (NANC) transmission, incorporating peptidergic and purinergic mechanisms.
• Significant developmental plasticity exists in the neural control of duodenal motility.