Neostigmine augments responses of the rat anococcygeus muscle to field stimulation.
1 The effects of neostigmine on noradrenergic transmission have been studied in the field stimulated, isolated anococcygeus muscle of the rat. 2 In those muscles where the excitatory response to field stimulation was not completely inhibited by guanethidine (5 X 10(-6) to 10(-5) M) or phentolamine (10(-6) M), atropine (5 X 10(-8) M) gave no further inhibition of the response. 3 The shape of the response to field stimulation was altered in a dose-dependent manner by neostigmine (5 X 10(-7) to 5 X 10(-6) M), such that a 'shoulder' appeared during the relaxation phase. The 'shoulder', present at all stimulation frequencies tested between 3 and 40 Hz, was abolished by atropine (5 X 10(-8) M) and unaffected by tubocurarine (10(-6) M). 4 Neostigmine (2.5 X 10(-6) M), whether alone or in the presence of atropine (5 X 10(-8) M), had no effect on the uptake or stimulation-induced release of [3H]-noradrenaline. 5 Using electron microscopy, small Schwann/axon bundles close to smooth muscle cells rarely showed cholinesterase staining, whereas larger bundles at the outer serosal aspects of the muscle exhibited dense staining. 6 It is concluded that the observed effects of neostigmine are not due to a presynaptic effect on noradrenergic transmission.
D000818:Animals; D002795:Choline O-Acetyltransferase / Q000037:antagonists & inhibitors; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects* / Q000648:ultrastructure; D009388:Neostigmine / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000187:drug effects; D009435:Synaptic Transmission / Q000187:drug effects
D002800:Cholinesterase Inhibitors; D009388:Neostigmine; D002795:Choline O-Acetyltransferase; D009638:Norepinephrine