Presynaptic and postsynaptic effects of mercuric ions on guinea-pig ileum longitudinal muscle strip preparation.
The toxic effect of mercuric ions on intestinal cholinergic neurotransmission was investigated in vitro. Hg2+ inhibited the evoked release and enhanced the resting release of ACh. Smooth muscle contraction was irreversibly inhibited by Hg2+ in a concentration-dependent manner, and Na2EDTA did not antagonize this effect. We also investigated if Hg2+ enters the nerve terminal through Ca(2+)-channels, or Na(+)-channels, or both. The effects of mercuric ions obtained in our study were completely abolished by the combined administration of TTX and Co2+. It is suggested that the site of the action of mercuric ions is intracellular. We concluded that Hg2+ may interfere with cholinergic transmission by blocking [Ca2+]o-dependent release of ACh and by enhancing [Ca2+]o-independent resting release of ACh. The effect of Hg2+ was not only presynaptic since it also inhibited the effect of ACh on smooth muscle.
Abram
Z
Z
Department of Hygiene and Occupational Medicine, Medical and Pharmacological University, Romania.
Korossy
S
S
D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002413:Cations, Divalent; D003035:Cobalt / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D006168:Guinea Pigs; D007082:Ileum; D008297:Male; D008628:Mercury / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D015222:Sodium Channels / Q000378:metabolism; D013569:Synapses / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D015220:Calcium Channels; D002413:Cations, Divalent; D015222:Sodium Channels; D003035:Cobalt; D013779:Tetrodotoxin; D008628:Mercury; D000109:Acetylcholine; D002118:Calcium