Characterizations And Temperature Sensitivities Of Whole-Cell L-Type Ca～(2+) Currents In The POAH Neurons Of Hypothalamus From Adult Rats

The essence of center temperature regulation is a researchful hotspot of fever pathological and heat environment medical fields. In mammals, multiple thermostats in several brain areas, e.g. the preoptic area and anterior hypothalamus (POAH), may regulate core temperature, whereas its cellular mechanism underlying their thermo-responsiveness is not completely clear.Voltage-gated Ca2+ channels (VGCCs) are pathways with high selectivity for Ca2+ that are opened by cell membrane depolarization. VDCC activation evokes a high rate of Ca2+ influx, driven by its high electrochemical gradient across the plasmalemma. The ensuing rise of cytosolic Ca2+ concentration ([Ca2+]j) acts as a second messenger. Thereinto, 50-70 percent of calcium influx via VGCC is through L-type calcium channels. Voltage-gated Ca2+ channels have a central role hi neuronal function and are essential for converting electrical activity into biochemical events. Specially, activation of the L-type Ca2+ channel (LTC) specifically increases the expression of a group of Ca²⁺-regulated genes, including those encoding c-Fos, brain-derived neurotrophic factor (BDNF), and Bcl-2, that have been shown to be required and important for neuronal functions.L-type Ca2+ channel currents have been extensively characterized in many kinds of neurons, but so far no exhaustive data are available for the preoptic-anterior hypothalamic neurons. Studies have showed Ca2+ channels are very sensitive to temperature. So the main purpose of the present work was first to carry out an electrophysiological and pharmacological thecharacterization of L-type calcium channels currents in POAH. And then examine whether L-type calcium channel currents in neurons of the preoptic area and anterior hypothalamus (POAH) were changed following warming using whole-cell configuration of patch clamp techniques.First, we successfully isolated POAH neurons acutely. Resting potentials from healthy cells were about -50 mV. The recording was steady when the potentials were clamped in the range -120mV to + 80mV.Whole cell recordings were obtained from POAH neurons acutely dissociated, a sustained inward current was activated by depolarizing voltage steps from a holding potential of -50mV with the use of either 2mM, 5 mM Ca2+ or 5 mM Ba2+ as the charge carrier respectively. The inward Ca2+ channel currents were first detected at around -30 mV,-l0mV and -40m V respectively. The peak currents occurred at OmV, l0mV and -10 mV for 2mM, 5 mM Ca2+ and 5 mM Ba2+, respectively. Increased [Ca2+] enhanced the peak current density in a hyperbolic manner. The curve was fitted by nonlinear regression in accordance with the equation Ica/Ica. , where I_Ca,max was 28.7 pA/pF and the association constant (K) of the Ca2+ binding site was 2.08 mM. The voltage dependence of the activation and inactivation of currents was assessed in an external solution containing 5 rnMBa2+. The the half-activation voltage, was -3.49 ?0.63 mV and k, a slope factor, was 11.77 ?1.37 mV per e-fold increase in conductance. The half-inactivation voltage was -8.04 ?1.23 mV and slope (K) is - 9.87 ?0.89mV.This channel currents we recorded could be blocked by Nifedipine and could be potentiated by Bay K 8644. Whole-cell voltage-clamp recordings indicated that warming increased the voltage-gated calcium currents and shifted the I-V curve to left.We studied systemically the biophysical and pharmacological characterization of L-type voltage-gated calcium currents in the hypothalamic neurons of POAH region of the adult rat and conclude that L-type calciumchannels is expressed in POAH neurons and is a key factor of thermostats. It is suggested that the functional enhancement in L-type calcium channels may partially account for the temperatures sensitive mechanism of hypothalamic POAH neurons following temperatures increase.II Anti-Fatigue Effect of S101 Compound Preparation in Heat Environment and Effects of S101 on L-calcium current in POAH neurons of hypothalamusIn order to find effective anti-fati...