The slow phase of the acetylcholine response in isolated neurons of the gastropod mollusc, Planorbarius corneus

The effect of cooling on the acetylcholine-induced current of identified Helix pomatia Br neuron

The Br neuron of the snail Helix pomatia, involved in neuronal regulation of various homeostatic and adaptive mechanisms, represents an interesting model for studying effects of temperature changes on neuronal activity of poikilotherms. The acetylcholine (ACh) induces a transient, inward dose-dependent current in the identified Br neuron. In the work presented, we analyses the effects of cooling on the ACh-induced inward current. The amplitude of ACh-induced inward current was markedly decreased after cooling and the speed of the decay of ACh response was decreased. Sensitivity to cooling of Ach-activated current on the Br neuron is mediated by a mechanism that does not involve change in the apparent receptor affinity or the cooperativity of binding.

Modification of the acetylcholine-induced current of the snail Helix pomatia L. by fast temperature changes

Using the single electrode voltage clamp method, we found that acetylcholine (aCh) induces transient inward dose-dependent current on the membrane of the identified Helix pomatia Br neuron. We analyzed the effects of fast cooling and heating as well as thermal acclimation on the aCh inward current. the experiments were conducted on active and dormant snails acclimated to either 20 or 7?C for at least four weeks. the Hill coefficient remained approximately 1 in all cases, which means that there is a single aCh binding site on the membrane. Fast temperature alternations induce binding affinity changes. in the work presented, we analyzed the effects of cooling on the aCh-induced inward current. the amplitude of aCh-induced inward current was markedly reduced after cooling, and the speed of decay of the aCh response was lower. <br><br><font color="red"><b> This article has been retracted. Link to the retraction <u><a href="http://dx.doi.org/10.2298/ABS1501341E">10.2298/ABS1501341E</a><u></b></font>

The muscle chemoreceptors of the ascidian Halocynthia aurantium

The body wall muscle of the ascidian, Halocynthia aurantium, is sensitive to both nicotinomimetics and muscarinomimetics. Atropine (4 X 10(-11 M) and benzilylcholine mustard (1 X 10(-5) M for 15 min) selectively block responses to muscarinomimetics. d-Tubocurarine (2 X 10(-6) M) and hexadecamethylene-bis-trimethylammonium (2 X 10(-7) M) prevent contractions induced by both nicotinomimetics and muscarinomimetics. In the cold season of the year the sensitivity of the muscle to muscarinomimetics disappears while responses to nicotinomimetics do not change throughout the year. The cooling of the water in the experimental bath results in an increase in the muscle contractions caused by muscarinomimetics while the responses to nicotinomimetic propionylcholine do not change. Catecholamines induce a decrease of the ascidian muscle responses to acetylcholine, cGMP and papaverine produce a similar effect.

Ionic mechanisms of the rapid (nicotinic) phase of acetylcholine response in identified Planobarius corneus neurones

Current responses to acetylcholine (ACh) and to suberyldicholine (D-6) applied from the double-barrelled ionophoretic micropipette were studied in two identified neurones (LPed-2 and LPed-3) isolated from the left ganglion of pulmonate mollusc, Planorbarius corneus. Experiments made with K2SO4-filled microelectrodes show that in LPed-2 neurone two kinds of cholinoreceptors are involved in the rapid phase of ACh response one of which induces chloride conductance and the other, sodium conductance. The Cl-dependent component can be separated from the cationic one by C-6 whereas the cationic component can be separated from the Cl--dependent one by furosemide. Cl- conductance can be induced selectively by D-6. In the LPed-3 neurone only Cl- conductance increases during rapid phase of ACh response. The reversal potential of Cl--dependent responses was found to be more negative than the resting potential in experiments made with K2SO4-filled microelectrodes but less negative than the resting potential in the case of KCl-filled microelectrodes. This difference seems to be due to the artificial increase of intracellular chloride concentration.

Mechanisms of slow postsynaptic potentials

Classical views of synaptic transmission have to be modified to take account of slow postsynaptic potentials (p.s.ps), which are often mediated by novel ionic and molecular mechanisms and which are sometimes evoked by neuropeptides. Understanding slow p.s.ps will provide insights into the mechanisms of biological signal transduction and long-term signalling in the nervous system.