title: Electrophysiological and pharmacological characterization of serotonergic dorsal raphe neurons recorded extracellularly and intracellularly in rat brain slices.
abstract: Extracellular and intracellular recordings were made from dorsal raphe (DR) neurons in frontal rat brain slices maintained in vitro. A population of neurons was found which displayed electrophysiological and pharmacological characteristics of serotonin-containing DR neurons recorded in vivo. Recorded extracellularly, these neurons displayed biphasic or triphasic action potentials of 1.5-3.0 ms duration, and discharged with a slow and steady rhythm. Recorded intracellularly these neurons displayed action potentials of about 1.8 ms duration, which were followed by large (10-20 mV) after hyperpolarizations which normally lasted 200-800 ms. These presumed serotonergic DR neurons were inhibited by LSD and serotonin. They were excited by norepinephrine, or the alpha-agonist phenylephrine, and these activations could be reduced or blocked by alpha-adrenoreceptor antagonists including the selective alpha 1-antagonist, prazosin. The major difference between the in vitro recordings and previous in vivo recordings from anesthetized animals was a reduction in the number of spontaneously firing DR neurons. This was probably due, at least in part, to a disfacilitation of serotonergic DR neurons in the slice caused by the functional removal of a tonic noradrenergic input.
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001933:Brain Stem / Q000502:physiology*; D046508:Culture Techniques; D004305:Dose-Response Relationship, Drug; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D007424:Intracellular Fluid / Q000502:physiology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000502:physiology; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011903:Raphe Nuclei / Q000502:physiology*; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D009435:Synaptic Transmission / Q000187:drug effects
chemical_list: D000317:Adrenergic alpha-Antagonists; D010656:Phenylephrine; D012701:Serotonin; D009638:Norepinephrine