title: Frequency dependence of 5-HT autoreceptor function in rat dorsal raphe and suprachiasmatic nuclei studied using fast cyclic voltammetry.
abstract: Fast cyclic voltammetry (FCV) at carbon fibre microelectrodes was used to monitor the time course of changes in extracellular concentration of endogenous 5-hydroxytryptamine ([5-HT]ex), in slices of rat brain containing either dorsal raphe nucleus (DRN) or suprachiasmatic nucleus (SCN). Five- or 20-pulse electrical stimulation trains were applied at frequencies between 5 and 500 Hz. [5-HT]ex was frequency and train length dependent, with maximum overflow in both sites at 100 Hz. Methiothepin (0.1 microM) caused a significant increase in [5-HT]ex when 5 pulses were applied at 5 Hz or when 20 pulses were applied at 10 or 20 Hz, but not at higher frequencies. When a single pseudo single pulse stimulation was used (5-pulse train at 100 Hz), methiothepin (0.1 microM) did not enhance [5-HT]ex in either the DRN or SCN; when 4 such pseudo single pulses were applied at 1 Hz methiothepin (0.1 microM) enhanced [5-HT]ex. A minimum period of stimulation of between 400 ms and 1 s was required for autoreceptor activation to occur in both regions. We conclude that [5-HT]ex can show a wide dynamic range of response to electrical stimulation, and that in both DRN and SCN it is subject to pulse-to-pulse regulation by presynaptic autoreceptors.
authors.affiliation: Department of Pharmacology, Queen Mary and Westfield College, London, U.K.
authors.forename: J J
authors.initials: JJ
authors.lastname: O'Connor
authors.forename: Z L
authors.initials: ZL
authors.lastname: Kruk
mesh_terms: D000818:Animals; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D008839:Microelectrodes; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011985:Receptors, Serotonin / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology*
chemical_list: D011985:Receptors, Serotonin; D012701:Serotonin; D008719:Methiothepin