title: 5-Hydroxytryptamine acts at 5-HT2 receptors to decrease potassium conductance in rat nucleus accumbens neurones.
abstract: 1. Intracellular recordings were made from neurones in the nucleus accumbens in slices from the rat brain maintained in vitro. 2. 5-Hydroxytryptamine (5-HT.1-100 microM) depolarized 170 of 203 (84%) neurones and caused them to discharge action potentials. The depolarization was associated with an increase in the input resistance, and was reversed in polarity by conditioning hyperpolarization; this reversal potential was linearly related to the logarithm of the extracellular potassium concentration. 3. Application of 5-HT to neurones voltage-clamped near their resting potential (typically about -80 mV) caused an inward current and a decrease in the slope conductance. The current caused by 5-HT reversed polarity at the potassium equilibrium potential. Analysis with an equivalent circuit model of the neurone at steady state indicated that 5-HT selectively reduced the inward rectifier potassium conductance. 4. The depolarization caused by 5-HT persisted in tetrodotoxin (1 microM). It was reduced but not abolished by a solution that contained lower levels of calcium (0.24 instead of 2.4 mM), higher levels of magnesium (5 instead of 1.2 mM), and cobalt (2 mM). 5. The depolarization caused by 5-HT was competitively antagonized by the 5-HT2 antagonists ketanserin and mianserin with dissociation equilibrium constants of 3 and 45 nM respectively: spiperone (300 nM) also blocked the action of 5-HT. The depolarization was not mimicked or blocked by a number of other agonists and antagonists selective for the 5-HT1 and 5-HT3 receptor types.
authors.affiliation: Vollum Institute, Oregon Health Sciences University, Portland 97201.
authors.forename: R A
authors.initials: RA
authors.lastname: North
authors.forename: N
authors.initials: N
authors.lastname: Uchimura
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008803:Mianserin / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D009714:Nucleus Accumbens / Q000166:cytology* / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D011985:Receptors, Serotonin / Q000187:drug effects* / Q000502:physiology; D012686:Septal Nuclei / Q000166:cytology*; D012701:Serotonin / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D015221:Potassium Channels; D011985:Receptors, Serotonin; D008803:Mianserin; D012701:Serotonin; D013779:Tetrodotoxin; D007650:Ketanserin