Biomaterial Database

Calcium spike underlying rhythmic firing in dopaminergic neurons of the rat substantia nigra. 1993

Y Kang, and S T Kitai

Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis 38163.

In order to study a possible mechanism for rhythmic firing of dopaminergic (DA) neurons, intracellular recordings were obtained from 56 rhythmically firing DA neurons in the rat substantia nigra compacta (SNc), using in vitro slice preparations. In the presence of TTX, spontaneous oscillation of the membrane potential was induced in SNc DA neurons when the membrane potential was depolarized more positive from -60 to -40 mV. Each oscillation wave was characterized by a pacemaker-like slow depolarization (PLSD) followed by a relatively prompt repolarization. As the DC depolarization was increased from -60 to -40 mV, the oscillation frequency increased from 0.5 to 5 Hz, but the amplitude of the wave decreased. Of 17 neurons tested in the presence of TTX, the maximum amplitudes of the oscillation varied from 10-15 mV in 8 neurons and were less than 5 mV in 9 neurons. In those 9 neurons, an application of TEA greatly enhanced (up to 15 mV) the amplitude of oscillation. The oscillation ceased when the membrane was hyperpolarized more negative than -60 mV. At the membrane potential more negative than -60 mV in the presence of TTX an injection of a depolarizing current pulse could evoke PLSD which was an all-or-nothing regenerative spike potential. The rate of rise of the PLSD changed depending on the intensity of injected current pulses but their amplitude remained constant. Its time-to-peak was slow (up to 1400 ms), while the decay time was relatively brief (< 500 ms). The threshold membrane potential for evoking PLSD was -53.7 +/- 3.2 mV (n = 10). This was higher than the previously reputed threshold for low threshold Ca2+ spike (LTS) (< -60 mV) and lower than that for high threshold Ca2+ spike (HTS) (> -35 mV) in SNc DA neurons. Even at a holding potential of -45 mV, a depolarizing current pulse could trigger PLSD while LTS was completely inactivated. Cd2+ (0.4 mM) abolished the oscillation and PLSD without marked effects on the LTS (n = 6). A low Ca2+ and high Mg2+ Ringer's solution also abolished the oscillation and PLSD (n = 4). An intracellular injection of EGTA markedly prolonged the decay time course of PLSD characterized by a slow and a relatively fast falling phase (n = 5). This would suggest an involvement of Ca(2+)-dependent K+ conductance and/or Ca2+ dependent inactivation of Ca2+ conductance during repolarization.(ABSTRACT TRUNCATED AT 400 WORDS)

UI	MeSH Term	Description	Entries
D007150	Immunohistochemistry	Histochemical localization of immunoreactive substances using labeled antibodies as reagents.	Immunocytochemistry,Immunogold Techniques,Immunogold-Silver Techniques,Immunohistocytochemistry,Immunolabeling Techniques,Immunogold Technics,Immunogold-Silver Technics,Immunolabeling Technics,Immunogold Silver Technics,Immunogold Silver Techniques,Immunogold Technic,Immunogold Technique,Immunogold-Silver Technic,Immunogold-Silver Technique,Immunolabeling Technic,Immunolabeling Technique,Technic, Immunogold,Technic, Immunogold-Silver,Technic, Immunolabeling,Technics, Immunogold,Technics, Immunogold-Silver,Technics, Immunolabeling,Technique, Immunogold,Technique, Immunogold-Silver,Technique, Immunolabeling,Techniques, Immunogold,Techniques, Immunogold-Silver,Techniques, Immunolabeling
D008297	Male		Males
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D009474	Neurons	The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.	Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D010641	Phenotype	The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.	Phenotypes
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D004298	Dopamine	One of the catecholamine NEUROTRANSMITTERS in the brain. It is derived from TYROSINE and is the precursor to NOREPINEPHRINE and EPINEPHRINE. Dopamine is a major transmitter in the extrapyramidal system of the brain, and important in regulating movement. A family of receptors (RECEPTORS, DOPAMINE) mediate its action.	Hydroxytyramine,3,4-Dihydroxyphenethylamine,4-(2-Aminoethyl)-1,2-benzenediol,Dopamine Hydrochloride,Intropin,3,4 Dihydroxyphenethylamine,Hydrochloride, Dopamine
D004594	Electrophysiology	The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.
D000200	Action Potentials	Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.	Spike Potentials,Nerve Impulses,Action Potential,Impulse, Nerve,Impulses, Nerve,Nerve Impulse,Potential, Action,Potential, Spike,Potentials, Action,Potentials, Spike,Spike Potential
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia