Cholinergic receptors in the extraocular rectus muscle of the rabbit.
The cholinergic receptors in rabbit isolated rectus muscle preparations were characterized by means of cholinergic agonists and antagonists. The concentration-dependent contraction induced by acetylcholine, carbachol or oxotremorine remained uninfluenced by atropine (10(-5) M), whereas the nicotinic receptor antagonist hexamethonium caused a parallel shift of the concentration-response curve. The agonists pilocarpine, methacholine and aceclidine, which are selective muscarinic receptor stimulants, did not cause contraction of the muscle preparation. However, the nicotinic receptor stimulant 1,1-dimethyl-4-phenylpiperazine iodide (DMPP) caused contraction similar to that induced by acetylcholine. DMPP-induced contractions were inhibited by hexamethonium, causing a parallel rightward shift of the concentration-response curve. This shift could be quantified by means of a Schild plot, indicating competitive antagonism with a PA2 value of 4.63 for hexamethonium. Atropine when applied together with hexamethonium did not cause a further shift of the concentration-response curve. The present results clearly indicate that the cholinergic receptors which mediate contraction in the rabbit isolated extraocular muscle preparation belong to the nicotinic subtype.
Rondas
A A
AA
Netherlands Ophthalmic Research Institute, Amsterdam.
Boddeke
H W
HW
Doods
H N
HN
Thörig
L
L
van Haeringen
N J
NJ
van Zwieten
P A
PA
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D005260:Female; D006584:Hexamethonium Compounds / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology; D009801:Oculomotor Muscles / Q000378:metabolism*; D010095:Oxotremorine / Q000494:pharmacology; D011817:Rabbits; D011950:Receptors, Cholinergic / Q000032:analysis*
D006584:Hexamethonium Compounds; D009466:Neuromuscular Blocking Agents; D011950:Receptors, Cholinergic; D004246:Dimethylphenylpiperazinium Iodide; D010095:Oxotremorine; D002217:Carbachol; D000109:Acetylcholine