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D 2 ‐like dopamine receptor activation excites rat dorsal raphe 5‐HT neurons in vitro
Author(s) -
HajDahmane Samir
Publication year - 2001
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.0953-816x.2001.01616.x
Subject(s) - depolarization , chemistry , quinpirole , dorsal raphe nucleus , biophysics , agonist , hyperpolarization (physics) , membrane potential , neuroscience , medicine , receptor , biology , serotonin , biochemistry , serotonergic , organic chemistry , nuclear magnetic resonance spectroscopy
The aim of the present study was to investigate the effect of dopamine (DA) on the excitability of dorsal raphe nucleus (DRN) 5‐hydroxytryptamine (5‐HT) neurons using the patch‐clamp technique in brain slices. Bath application of DA (1–300 µ m ) produced a concentration‐dependent membrane depolarization in all 5‐HT neurons examined. This effect persisted in the presence of tetrodotoxin (TTX; 1 µ m ) and low extracellular calcium. Moreover, blockade of ionotropic glutamate receptors with 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX) and 2‐amino‐5‐phosphonopentanoic acid (AP5) did not prevent DA‐induced depolarization, indicating that it was mediated by a direct effect of DA on 5‐HT neurons. The DA‐induced depolarization was not antagonized by selective α 1 ‐adrenergic receptor antagonists, prazosin and WB 4101, but by a nonselective DA receptor antagonist, haloperidol. In addition, the selective D 2 ‐like receptor agonist quinpirole and antagonist sulpiride mimicked and blocked DA‐induced depolarization, respectively. These results indicate that DA‐induced membrane depolarization in DRN 5‐HT neurons is mediated by the activation of D 2 ‐like DA receptors. The DA‐induced membrane depolarization and inward current were associated with an increase in membrane conductance. Examination of the current–voltage (I–V) relationship for the DA‐induced inward current revealed that the amplitude of the current increased with membrane hyperpolarization and reversed polarity at a potential near −15 mV. These data suggest that DA‐induced depolarization in DRN 5‐HT neurons is not mediated by a decrease in potassium conductance, but most likely by the activation of a nonselective cation current.