Intracellular recording in avian brain of a nicotinic response that is insensitive to K-bungarotoxin.
We examined nicotinic acetylcholine receptors in the avian brain using a combination of autoradiographic and intracellular electrophysiological techniques. We found that the lateral spiriform nucleus (SPL) in the mesencephalon has a very high density of 3H-nicotine binding sites but no detectable 125I-K-bungarotoxin (125I-K-BuTx) or 125I-alpha-bungarotoxin (125I-alpha-BuTx) bindings sites. Intracellular recordings in brain slices revealed that SPL neurons depolarize in response to nicotine and carbachol (in the presence of atropine). These depolarizations were blocked by the classic nicotinic antagonists d-tubocurarine and dihydro-beta-erythroidine. As predicted for nicotinic receptors with a high affinity for nicotine, neither K-BuTx nor alpha-BuTx blocked these nicotinic responses. Thus, although the existence of high-affinity 3H-nicotine binding sites has been known for some time, we now report the in situ detection of a functional nicotinic receptor that has a high affinity for nicotine and is K-BuTx-insensitive.
Department of Pharmacology, St. Louis University School of Medicine, Missouri 63104.
E M
EM
Sorenson
V A
VA
Chiappinelli
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000166:cytology / Q000187:drug effects*; D002038:Bungarotoxins / Q000494:pharmacology*; D002217:Carbachol / Q000494:pharmacology; D002645:Chickens; D004079:Dihydro-beta-Erythroidine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology / Q000379:methods; D005260:Female; D007425:Intracellular Membranes / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009538:Nicotine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009994:Osmolar Concentration; D014403:Tubocurarine / Q000494:pharmacology
D002038:Bungarotoxins; D004079:Dihydro-beta-Erythroidine; D009538:Nicotine; D002217:Carbachol; D014403:Tubocurarine