Actions of 5-hydroxytryptamine on ventral tegmental area neurons of the rat in vitro.
Intracellular recordings were made with conventional microelectrodes and with whole-cell patch-clamp electrodes from neurons of the rat ventral tegmental area and substantia nigra zona compacta in vitro. Neurons were distinguished as principal cells and secondary cells; it is known from previous work that most principal cells contain dopamine whereas secondary cells do not. 5-Hydroxytryptamine (5-HT; 3-100 microM) depolarized (or evoked an inward current at -60 mV) 46% of 153 principal cells; a small proportion (11%) of cells were hyperpolarized (or showed outward current at -60 mV). Secondary cells were equally likely to be depolarized (or inward current at -60 mV, 30% of 80 cells) or hyperpolarized (or outward current at -60 mV, 28%). approximately 40% of each type of cell were unaffected by 5-HT. Depolarizing responses of 5-HT were mimicked by (+/-)-1-(2,5-dimethoxy-4-iodophenyl)- 2-aminopropane (DOI) and blocked by ketanserin. Hyperpolarizing responses were mimicked by dipropyl-5-carboxamidotryptamine and reversed polarity at the K+ equilibrium potential. Inhibitory postsynaptic potentials (or currents) mediated at GABAA receptors occurred spontaneously in some principal cells; they were reversibly blocked by tetrodotoxin and bicuculline. 5-HT either increased or decreased the frequency of these synaptic potentials but did not change their mean amplitude or decay time.(ABSTRACT TRUNCATED AT 250 WORDS)
Pessia
M
M
Vollum Institute, Oregon Health Sciences University, Portland 97201.
Jiang
Z G
ZG
North
R A
RA
Johnson
S W
SW
D000662:Amphetamines / Q000494:pharmacology; D000818:Animals; D001640:Bicuculline / Q000031:analogs & derivatives / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005071:Evoked Potentials / Q000187:drug effects*; D066298:In Vitro Techniques; D007650:Ketanserin / Q000494:pharmacology; D008297:Male; D008839:Microelectrodes; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000502:physiology; D012701:Serotonin / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects; D013681:Tegmentum Mesencephali / Q000502:physiology*; D013779:Tetrodotoxin / Q000494:pharmacology
D000662:Amphetamines; D011963:Receptors, GABA-A; D017366:Serotonin Receptor Agonists; D012701:Serotonin; C017069:bicuculline methiodide; D013779:Tetrodotoxin; D007650:Ketanserin; C015952:4-iodo-2,5-dimethoxyphenylisopropylamine; D004298:Dopamine; D001640:Bicuculline