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.
Netherlands Ophthalmic Research Institute, Amsterdam.
A A
AA
Rondas
H W
HW
Boddeke
H N
HN
Doods
L
L
Thörig
N J
NJ
van Haeringen
P A
PA
van Zwieten
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