A 5-HYDROXYTRYPTAMINE(2) AGONIST AUGMENTS GAMMA-AMINOBUTYRIC-ACID ANDEXCITATORY AMINO-ACID INPUTS TO NORADRENERGIC LOCUS-CERULEUS NEURONS

Citation
C. Chiang et G. Astonjones, A 5-HYDROXYTRYPTAMINE(2) AGONIST AUGMENTS GAMMA-AMINOBUTYRIC-ACID ANDEXCITATORY AMINO-ACID INPUTS TO NORADRENERGIC LOCUS-CERULEUS NEURONS, Neuroscience, 54(2), 1993, pp. 409-420
Citations number
76
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Neurosciences
Journal title
ISSN journal
0306-4522
Volume
54
Issue
2
Year of publication
1993
Pages
409 - 420
Database
ISI
SICI code
0306-4522(1993)54:2<409:A5AAGA>2.0.ZU;2-7
Abstract
We examined the effects of the 5-hydroxytryptamine2 receptor agonist, +/-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, on spontaneous and evoked discharge of locus coeruleus neurons in the rat. Extracellular recordings were obtained from single locus coeruleus neurons while (+/ -)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane was injected systemica lly or locally into the locus coeruleus. Systemic, but not local, admi nistration of (+/-)1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane decre ased spontaneous discharge of locus coeruleus neurons in a dose-depend ent manner while simultaneously increasing responses evoked by somatos ensory stimulation, consistent with previous studies using 5-hydroxytr yptamine2 agonists. Increased responsiveness was observed after both l ow- and high-intensity stimulation and, in the latter, resulted from t he addition of a second, longer latency response after (+/-)1-(2,5-dim ethoxy-4-iodophenyl)-2-aminopropane administration, when cells typical ly responded to each stimulation with two driven spikes instead of one . Both of these effects could be completely reversed by systemic admin istration of the 5-hydroxytryptamine2 receptor antagonist, ketanserin. Furthemore, we report that: (i) the 2,5-dimethoxy-4-iodophenyl)-2-ami nopropane-induced decrease in spontaneous firing was blocked by local infusion of the GABA antagonists bicuculline or picrotoxin into the lo cus coeruleus, but not by local infusion of the alpha-2 adrenoceptor a ntagonist, idazoxan; and (ii) the enhancement of locus coeruleus senso ry responses after high-intensity stimulation was blocked by local app lication of the selective antagonist of N-methyl-D-aspartate receptors , 2-amino-5-phosphonopentanoic acid, but not by local infusion of the preferential antagonist of non-N-methyl-D-aspartate receptors, 6-cyano -7-nitroquinoxaline-2,3-dione. Together, these results lead us to prop ose that systemic 5-hydroxytryptamine2 agonists influence locus coerul eus indirectly, causing tonic activation of a GABAergic input to the l ocus coeruleus, and facilitating sensory inputs that act via excitator y amino acid receptors within locus coeruleus.