Inhibitory neuromuscular transmission to ileal longitudinal muscle predominates in neonatal guinea pigs.
BACKGROUND
Inhibitory neurotransmission to the longitudinal muscle is more prominent in the neonatal than in the adult guinea pig ileum.


METHODS
Inhibitory neuromuscular transmission was investigated using in vitro ileal longitudinal muscle myenteric plexus (LMMP) preparations made from neonatal (< or =48 h postnatal) and adult ( approximately 4 weeks postnatal) guinea pigs.


RESULTS
Amperometric measurements of nicotine-induced nitric oxide (NO) release (measured as an oxidation current) from myenteric ganglia revealed larger currents in neonatal (379 +/- 24 pA) vs adult (119 +/- 39 pA, P < 0.05) tissues. Nicotine-induced oxidation currents were blocked by the nitric oxide synthase (NOS) inhibitor, nitro-l-arginine (NLA, 100 micromol L(-1)). Nicotine-induced, NLA-sensitive oxidation currents could be detected in the tertiary plexus of neonatal but not adult tissues. Immunohistochemistry demonstrated stronger NOS immunoreactivity in neonatal compared with adult myenteric ganglia. Western blot studies revealed higher levels of NOS in neonatal compared with adult LMMP. Cell counts revealed that the total number of myenteric neurons in the small intestine was greater in adults than in neonatal guinea pigs, however, the ratio of NOS : Calbindin neurons was significantly higher in neonatal compared with adult tissues.


CONCLUSIONS
Nitric oxide signaling to the longitudinal muscle is stronger in neonatal compared with adult guinea pig ileum. Nitric oxide synthase-containing neurons are diluted postnatally by cholinergic and other, as yet unidentified neuronal subtypes.
Patel
B A
BA
Department of Chemistry, Michigan State University, East Lansing, MI, USA.
Dai
X
X
Burda
J E
JE
Zhao
H
H
Swain
G M
GM
Galligan
J J
JJ
Bian
X
X
D000818:Animals; D000831:Animals, Newborn; D064026:Calbindins; D004566:Electrodes; D006168:Guinea Pigs; D007082:Ileum / Q000033:anatomy & histology* / Q000187:drug effects / Q000254:growth & development; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D009197:Myenteric Plexus / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D019335:Nitroarginine / Q000494:pharmacology; D011978:Receptors, Nicotinic / Q000378:metabolism; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D064026:Calbindins; D011978:Receptors, Nicotinic; D064030:S100 Calcium Binding Protein G; D019335:Nitroarginine; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase