title: Muscarinic signalling affects intracellular calcium concentration during the first cell cycle of sea urchin embryos.
abstract: The existence of a response to acetylcholine (ACh) and cholinomimetic drugs in sea urchin eggs and zygotes was investigated in two sea urchin species: Paracentrotus lividus and Lytechinus pictus. The calcium sensitive fluorescent probe, Fura-2 dextran, was employed to investigate the regulation of cytosolic free calcium concentration ([Ca(2+)](i)) by cholinomimetic drugs in unfertilised and fertilised eggs of both the sea urchin species. Exposure to cholinomimetic agonists/antagonists, either extracellularly or intracellularly, had no effect either on resting [Ca(2+)](i) levels in the unfertilised sea urchin egg, or on the transient [Ca(2+)](i) increase at fertilisation. However, following fertilisation, extracellular application of ACh receptors agonists, such as ACh and carbachol, predominantly muscarinic agonist, but not nicotine, induced a significant increase in [Ca(2+)](i), which was partially inhibited by atropine. As a consequence of exposure after fertilisation to the agonists of ACh receptors, chromatin structure was transiently affected. The hypothesis is proposed that muscarinic receptors may be involved in the (presumably Ca(2+)-dependent) modulation of the nuclear status during the first cell cycles.
authors.affiliation: Department of Physiological Sciences, Medical School, University of Newcastle Upon Tyne, UK.
authors.forename: P K
authors.initials: PK
authors.lastname: Harrison
authors.forename: C
authors.initials: C
authors.lastname: Falugi
authors.forename: C
authors.initials: C
authors.lastname: Angelini
authors.forename: M J
authors.initials: MJ
authors.lastname: Whitaker
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002453:Cell Cycle / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D003911:Dextrans / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005306:Fertilization; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D016257:Fura-2 / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008845:Microinjections; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology; D010063:Ovum / Q000187:drug effects / Q000502:physiology; D011976:Receptors, Muscarinic / Q000378:metabolism*; D012617:Sea Urchins / Q000187:drug effects / Q000196:embryology* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism
chemical_list: D018679:Cholinergic Agonists; D003911:Dextrans; D005456:Fluorescent Dyes; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D009538:Nicotine; D001285:Atropine; D002217:Carbachol; D000109:Acetylcholine; D002118:Calcium; D016257:Fura-2