Journal
NEUROSCIENCE
Volume 116, Issue 3, Pages 669-683Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0306-4522(02)00584-5
Keywords
5-HT; 5-HT1A receptor; intracellular; slice; rat
Categories
Funding
- NATIONAL INSTITUTE OF MENTAL HEALTH [RC1MH089800, R01MH075047, R01MH063078, P01MH048125, R01MH058250, F32MH012274, R21MH099488, R03MH060773, R56MH058250] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE [R01NS028512] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS [R01DC004098] Funding Source: NIH RePORTER
- NIDCD NIH HHS [DC 04098] Funding Source: Medline
- NIMH NIH HHS [MH 12274, R01 MH063078-01, P01 MH048125, RC1 MH089800, R21 MH099488, MH63078, R03 MH060773-01A2, MH 58250, R01 MH063078, R01 MH075047-01A1, R01 MH075047, F32 MH012274, MH60773, R03 MH060773-02] Funding Source: Medline
- NINDS NIH HHS [R01 NS028512, NS 28512] Funding Source: Medline
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The membrane properties and receptor-mediated responses of rat dorsal raphe nucleus neurons were measured using intracellular recording techniques in a slice preparation. After each experiment, the recorded neuron was filled with neurobiotin and immunohistochemically identified as 5-hydroxytryptamine (5-HT)-immunopositive or 5-HT-immunonegative. The cellular characteristics of all recorded neurons conformed to previously determined classic properties of serotonergic dorsal raphe nucleus neurons: slow, rhythmic activity in spontaneously active cells, broad action potential and large afterhyperpolarization potential. Two electrophysiological characteristics were identified that distinguished 5-HT from non-5-HT-containing cells in this study. In 5-HT-immunopositive cells, the initial phase of the afterhyperpolarization potential was gradual (tau=7.3+/-1.9) and in 5-HT-immunonegative cells it was abrupt (tau=1.8+/-0.6). In addition, 5-HT-immunopositive cells had a shorter membrane time constant (tau=21.4+/-4.4) than 5-HT-immunonegative cells (tau=33.5+/-4.2). Interestingly, almost all recorded neurons were hyperpolarized in response to stimulation of the inhibitory 5-HT1A receptor. These results suggested that 5-HT1A receptors are present on non-5-HT as well as 5-HT neurons. This was confirmed by immunohistochemistry showing that although the majority of 5-HT-immunopositive cells in the dorsal raphe nucleus were double-labeled for 5-HT1A receptor-IR, a small but significant population of 5-HT-immunonegative cells expressed the 5-HT1A receptor. These results underscore the heterogeneous nature of the dorsal raphe nucleus and highlight two membrane properties that may better distinguish 5-HT from non-5-HT cells than those typically reported in the literature. In addition, these results present electrophysiological and anatomical evidence for the presence of 5-HT1A receptors on non-5-HT neurons in the dorsal raphe nucleus. (C) 2003 IBRO. Published by Elsevier Science Ltd. All rights reserved.
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