Barresi M, Li Volsi G, Licata F, Ciranna L, Santangelo F
University of Catania, Department of Physiological Sciences, Viale Andrea Doria 6, 95125 Catania.
Arch Ital Biol. 2005 Feb;143(1):13-27.
The effects of 5-hydroxytryptamine (5-HT) on neuronal firing rate were studied in the reticular gigantocellular nucleus (GRN) and, for a comparison, in the interstitial (IRN), the parvicellular (PRN) and the lateral (LRN) nuclei, sharing some of GRN functional characteristics. Unitary extracellular recordings performed in anesthetized rats demonstrated that microiontophoretic application of 5-HT modulated the background firing rate in 92% of GRN, in 100% of IRN and LRN, and in 77% of PRN tested neurons. In GRN, 5-HT application induced excitatory responses in 49% of the neurons tested and inhibitions in 43% of them. Both types of effects were dose dependent and appeared scattered throughout the nucleus. Enhancements and decreases of firing rate in response to 5-HT application were also recorded in IRN (58% and 42% respectively), LRN (43% and 57%) and PRN (36% and 41%). The 5-HT(1A) receptor agonist 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT) mimicked 5-HT evoked inhibitions in all the nuclei tested and induced weak inhibitory responses also in neurons excited by 5-HT. The 5-HT2A receptor agonist alphamethyl-5-hydroxytryptamine (alpha-me-5-HT) mimicked excitatory as well as inhibitory responses to 5-HT, the former prevailing in GRN and the latter in the remaining reticular nuclei. Both excitatory and inhibitory responses to 5-HT were partially or totally blocked by the application of 5-HT2 receptor antagonist ketanserin. It is concluded that an extended, strong and differentiated control is exerted by 5-HT on the electrical activity of bulbar reticular neurons. Both 5-HT(1A) and 5-HT(2A) receptors mediate these effects, but the involvement of other receptors appears probable.
研究了5-羟色胺（5-HT）对网状巨细胞核（GRN）神经元放电频率的影响，并与具有GRN部分功能特征的中间核（IRN）、小细胞网状核（PRN）和外侧网状核（LRN）进行比较。在麻醉大鼠中进行的单细胞胞外记录表明，通过微离子电泳施加5-HT可调节92%的GRN、100%的IRN和LRN以及77%的受试PRN神经元的背景放电频率。在GRN中，施加5-HT可使49%的受试神经元产生兴奋反应，43%的受试神经元产生抑制反应。这两种效应均呈剂量依赖性，且在整个核内呈散在分布。在IRN（分别为58%和42%）、LRN（43%和57%）和PRN（36%和41%）中也记录到了施加5-HT后放电频率的增加和降低。5-HT（1A）受体激动剂8-羟基-2（二正丙基氨基）四氢萘（8-OH-DPAT）模拟了5-HT在所有受试核中引起的抑制作用，并且在被5-HT兴奋的神经元中也诱导了微弱的抑制反应。5-HT2A受体激动剂α-甲基-5-羟色胺（α-me-5-HT）模拟了对5-HT的兴奋和抑制反应，前者在GRN中占主导，后者在其余网状核中占主导。对5-HT的兴奋和抑制反应在施加5-HT2受体拮抗剂酮色林后部分或完全被阻断。得出的结论是，5-HT对延髓网状神经元的电活动施加了广泛、强烈且有差异的控制。5-HT（1A）和5-HT（2A）受体均介导这些效应，但其他受体参与其中的可能性也很大。
