Linked Life Data

9307104

Source:http://linkedlifedata.com/resource/pubmed/id/9307104

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
2
pubmed:dateCreated
1997-10-23
pubmed:abstractText
Dopamine (DA) decreases activity in many hypothalamic neurons. To determine the mechanisms of DA's inhibitory effect, whole cell voltage- and current-clamp recordings were made from primary cultures of rat hypothalamic and arcuate nucleus neurons (n = 186; 15-39 days in vitro). In normal buffer, DA (usually 10 microM; n = 23) decreased activity in 56% of current-clamped cells and enhanced activity in 22% of the neurons. In neurons tested in the presence of glutamate receptor antagonists D,L-2-amino-5-phosphonovalerate (AP5; 100 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 10 microM), DA application (10 microM) revealed heterogeneous effects on electrical activity of cells, either hyperpolarization and decrease in activity (53% of 125) or depolarization and increase in spontaneous activity (22% of 125). The DA-mediated hyperpolarization of membrane potential was associated with a decrease in the input resistance. The reversal potential for the DA-mediated hyperpolarization was -97 mV, and it shifted in a positive direction when the concentration of K+ in the incubating medium was increased, suggesting DA activation of K+ channels. Because DA did not have a significant effect on the amplitude of voltage-dependent K+ currents, activation of voltage-independent K+ currents may account for most of the hyperpolarizing actions of DA. DA-mediated hyperpolarization and depolarization of neurons were found during application of the Na+ channel blocker tetrodotoxin (1 microM). The hyperpolarization was blocked by the application of DA D2 receptor antagonist eticlopride (1-20 microM; n = 7). In the presence of AP5 and CNQX, DA (10 microM) increased (by 250%) the frequency of spontaneous inhibitory postsynaptic currents (IPSCs) in 11 of 19 neurons and evoked IPSCs in 7 of 9 cells that had not previously shown any IPSCs. DA also increased the regularity and the amplitude (by 240%) of spontaneous IPSCs in 9 and 4 of 19 cells, respectively. Spontaneous and DA-evoked IPSCs and inhibitory postsynaptic potentials were blocked by the gamma-aminobutyrate A (GABA(A)) antagonist bicuculline (50 microM), verifying their GABAergic origin. Pertussis toxin pretreatment (200 ng/ml; n = 15) blocked the DA-mediated hyperpolarizations, but did not prevent depolarizations (n = 3 of 15) or increases in IPSCs (n = 6 of 10) elicited by DA. Intracellular neurobiotin injections (n = 21) revealed no morphological differences between cells that showed depolarizing or hyperpolarizing responses to DA. Immunolabeling neurobiotin-filled neurons that responded to DA (n = 13) showed that GABA immunoreactive neurons (n = 4) showed depolarizing responses to DA, whereas nonimmunoreactive neurons (n = 9) showed both hyperpolarizing (n = 6) and depolarizing (n = 3) responses. DA-mediated hyperpolarization, depolarization, and increases in frequency of postsynaptic activity could be detected in embryonic hypothalamic or arcuate nucleus neurons after only 5 days in vitro, suggesting that DA could play a modulatory role in early development. These findings suggest that DA inhibition in hypothalamic and arcuate nucleus neurons is achieved in part through the direct inhibition of excitatory neurons, probably via DA D2 receptors acting through a Gi/Go protein on K+ channels, and in part through the enhancement of GABAergic neurotransmission.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0022-3077
pubmed:author
pubmed:issnType
Print
pubmed:volume
78
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
674-88
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed-meshheading:9307104-2-Amino-5-phosphonovalerate, pubmed-meshheading:9307104-6-Cyano-7-nitroquinoxaline-2,3-dione, pubmed-meshheading:9307104-Animals, pubmed-meshheading:9307104-Arcuate Nucleus, pubmed-meshheading:9307104-Dopamine, pubmed-meshheading:9307104-Excitatory Amino Acid Antagonists, pubmed-meshheading:9307104-Glutamic Acid, pubmed-meshheading:9307104-Hypothalamus, pubmed-meshheading:9307104-Membrane Potentials, pubmed-meshheading:9307104-Neurons, pubmed-meshheading:9307104-Patch-Clamp Techniques, pubmed-meshheading:9307104-Pertussis Toxin, pubmed-meshheading:9307104-Potassium Channels, pubmed-meshheading:9307104-Rats, pubmed-meshheading:9307104-Rats, Sprague-Dawley, pubmed-meshheading:9307104-Virulence Factors, Bordetella, pubmed-meshheading:9307104-gamma-Aminobutyric Acid
pubmed:year
1997
pubmed:articleTitle
Dopamine inhibition: enhancement of GABA activity and potassium channel activation in hypothalamic and arcuate nucleus neurons.
pubmed:affiliation
Department of Biological Sciences, Stanford University, California 94305, USA.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, U.S. Gov't, Non-P.H.S., Research Support, Non-U.S. Gov't