Identification and electrophysiology of isolated pars compacta neurons from guinea-pig substantia nigra.
Single neurons from the substantia nigra of the adult guinea-pig were dissociated. Two morphological types of neurons were identified: (i) large multipolar neurons (20-40 microns greatest diameter) and (ii) small fusiform neurons (less than 20 microns diameter). Neurons of both types showed catecholamine fluorescence and were retrogradely labelled by rhodamine-conjugated microspheres injected into the striatum. Two types of neuron (Type A and Type B) were also identified electrophysiologically in perforated patch recordings of membrane potential and whole-cell current. Type A neurons had a low spontaneous firing frequency (5 Hz) broad action potentials (4 ms) and a threshold of approximately -45 mV. They were inhibited by the dopamine D2 receptor agonist, quinpirole. Type B neurons were characterized by a faster firing frequency (25 Hz), shorter action potential duration (1.5 ms) and a threshold of approximately -50 mV. These cells were unaffected by quinpirole. Large multipolar neurons were usually found to be of the A type and small fusiform, neurons of the B type. The properties of the large multipolar, Type A neurons suggest that they form part of the nigrostriatal, dopaminergic population of the pars compacta.
University Laboratory of Physiology, Oxford, U.K.
A H
AH
Hainsworth
J
J
Röper
R
R
Kapoor
F M
FM
Ashcroft
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002395:Catecholamines / Q000378:metabolism; D015259:Dopamine Agents / Q000494:pharmacology; D004594:Electrophysiology; D004873:Ergolines / Q000494:pharmacology; D005453:Fluorescence; D006168:Guinea Pigs; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D019257:Quinpirole; D011954:Receptors, Dopamine / Q000187:drug effects; D017448:Receptors, Dopamine D2; D012235:Rhodamines; D013378:Substantia Nigra / Q000166:cytology / Q000502:physiology*; D013469:Sulpiride / Q000494:pharmacology; D013569:Synapses / Q000502:physiology
D002395:Catecholamines; D015259:Dopamine Agents; D004873:Ergolines; D018377:Neurotransmitter Agents; D011954:Receptors, Dopamine; D017448:Receptors, Dopamine D2; D012235:Rhodamines; D019257:Quinpirole; D013469:Sulpiride