Pontine cholinergic respiratory depression in neonatal and young rats.
We postulated that activation of pontine cholinergic mechanisms would cause respiratory depression in neonatal and young rats. Phrenic activity was recorded in decerebrate, paralyzed, ventilated and vagotomized rats of 4 to 22 days after birth. Small volumes (10-60 nl) of carbachol (44-88 mM) were injected into the medial portion of the rostral pons. The injection of carbachol, but not saline, decreased phrenic peak activity (83 +/- 6% of control) and respiratory frequency (64 +/- 9.5% of control) within 2 min following the injection in neonates and the depression lasted for less than 10 min. The site of injection in the pontine reticular formation was confirmed by histology. Results suggest that cholinergic mechanisms in the medial pons depress respiratory activity in the neonate.
Fung
M L
ML
Department of Physiology, The University of Hong Kong. fungml@hkucc.hku.hk
St John
W M
WM
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D002217:Carbachol / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D008297:Male; D008845:Microinjections; D018721:Muscarinic Agonists / Q000008:administration & dosage / Q000494:pharmacology; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology; D011149:Pons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011950:Receptors, Cholinergic / Q000378:metabolism*; D012119:Respiration / Q000187:drug effects; D012131:Respiratory Insufficiency / Q000209:etiology / Q000503:physiopathology; D012132:Respiratory Muscles / Q000502:physiology; D012154:Reticular Formation / Q000187:drug effects / Q000502:physiology
D018721:Muscarinic Agonists; D011950:Receptors, Cholinergic; D002217:Carbachol