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Excitatory actions of serotonin on GABAergic neurons of the medial septum and diagonal band of broca
Author(s) -
Alreja Meenakshi
Publication year - 1996
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/(sici)1098-2396(199601)22:1<15::aid-syn2>3.0.co;2-l
Subject(s) - gabaergic , neuroscience , diagonal band of broca , bicuculline , cholinergic , excitatory postsynaptic potential , inhibitory postsynaptic potential , acetylcholine , interneuron , serotonin , 5 ht receptor , chemistry , cholinergic neuron , gabaa receptor , biology , receptor , endocrinology , biochemistry
The physiological and pharmacological actions of serotonin (5‐HT) on neurons in themedial septum and diagonal band of Broca (MSDB) were examined using extracellular andintracellular recording techniques in an in vitro rat brain‐slice preparation. In addition topreviously described inhibitory effects, novel excitatory actions of 5‐HT on GABA‐type cellswere observed. In intracellular recordings with KCl‐containing electrodes, bath‐applied 5‐HTinduced a bicuculline and tetrodotoxin‐sensitive increase in the number of reverse IPSPs inboth cholinergic‐ and noncholinergic‐type neurons (presumably GABAergic). In brain sliceswhere all structures neighboring the MSDB, including the lateral septum, had been excised, asimilar increase in 5‐HT‐induced IPSPs occurred, indicating that 5‐HT‐induced IPSPs in bothcholinergic‐ and noncholinergic‐type neurons originate from GABAergic neurons within theMSDB itself. Accordingly, GABA‐type neurons in the MSDB were found to be directlyexcited by 5‐HT. MDL 100,907, a selective 5‐HT 2A antagonist, blocked5‐HT‐induced excitations in a majority of neurons (58%). ICS 205‐930, a5‐HT 3 /5‐HT 4 antagonist, or mianserin, a nonselective 5‐HTantagonist, blocked most MDL‐resistant responses, indicating a role for multiple 5‐HTreceptor subtypes. This study also provides the first electrophysiological evidence for synaptic interactionsbetween 5‐HT‐activated GABAergic neurons and cholinergic neurons and amongstGABAergic neurons in the MSDB. The implications of the findings vis‐à‐visintraseptal circuitry and septohippocampal circuitry are discussed. © 1996 Wiley‐Liss,Inc.