Thermoreception of Paramecium: Different Ca 2+ Channels Were Activated by Heating and Cooling

Abstract

A Paramecium cell responded to heat and cold stimuli, exhibiting increased frequency of directional changes in its swimming behavior. The increase in the frequency of directional changes was maintained during heating, but was transient during cooling. Although variations were large, as expected with this type of electrophysiological recording, results consistently showed a sustained depolarization of deciliated cells in response to heating. Depolarizations were also consistently observed upon cooling. However, these depolarizations were transient and not continuous throughout the cooling period. These depolarizations were lost or became small in Ca2+-free solutions. In a voltage-clamped cell, heating induced a continuous inward current and cooling induced a transient inward current under conditions where K+ currents were suppressed. The heat-induced inward current was not affected significantly by replacing extracellular Ca2+ with equimolar concentrations of Ba2+, Sr2+, Mg2+, or Mn2+, and was lost upon replacing with equimolar concentration of Ni2+. On the other hand, the cold-induced inward current was not affected significantly by Ba2+, or Sr2+, however the decay of the inward current was slowed and was lost or became small upon replacing with equimolar concentrations of Mg2+, Mn2+, or Ni2+. These results indicate that Paramecium cells have heat-activated Ca2+ channels and cold-activated Ca2+ channels and that the cold-activated Ca2+ channel is different from the heat-activated Ca2+ channel in the ion selectivity and the calcium-dependent inactivation.

<i>Paramecium caudatum</i> Avoids from Naloxone

“…Our previous results have also implicated NO in the morphine effect by NADPHdiaphorase cytochemistry [1]. It has been postulated that several NO-sensitive targets, including guanylyl cyclase, potassium channels and voltage gated calcium channels [21,22,23,24,25] are stimulated in invertebrates. Other studies using the ciliate protozoan Stentor have demonstrated that these types of microorganisms express a G protein-mediated response to morphine when stimulated mechanically [26].…”

Cellular responses to mild heat stress

“…The sensing of heat stress requires two cysteine residues (C35 and C105), localized within or nearby the HSF1 DNA binding domain, that are required for disulfide bond formation and HSF1 activation in response to heat stress [41][42][43][44][45]. In addition, ion channel activities reflect the temperature applied [68][69][70][71]. Activities of ion channels such as Na + /K + and Ca 2+ flux of mammals are highly sensitive to the change in ambient temperatures and thus suggested to be a kind of thermoreceptor or thermosensor that is involved in the perception of temperature [70].…”

Human Sperm Thermotaxis Is Mediated by Phospholipase C and Inositol Trisphosphate Receptor Ca2+ Channel1

“…However, there is no indication that these TRPC Ca 2þ channels can function as thermosensors. Other channels reported as thermosensors (but not belonging to the TRP family) are heat-activated and cold-activated Ca 2þ channels in the ciliate Paramecium, each with a different ion selectivity [34], a heatactivated K þ channel in sponges [35], and a heat-activated background channel (KCNK2 or TREK-1) in the peripheral sensory neurons and central hypothalamic neurons [36].…”