title: Quantitative unit classification of ventral tegmental area neurons in vivo.
abstract: Neurons in the ventral tegmental area (VTA) synthesize several major neurotransmitters, including dopamine (DA), GABA, and glutamate. To classify VTA single-unit neural activity from freely moving rats, we used hierarchical agglomerative clustering and probability distributions as quantitative methods. After many parameters were examined, a firing rate of 10 Hz emerged as a transition frequency between clusters of low-firing and high-firing neurons. To form a subgroup identified as high-firing neurons with GABAergic characteristics, the high-firing classification was sorted by spike duration. To form a subgroup identified as putative DA neurons, the low-firing classification was sorted by DA D2-type receptor pharmacological responses to quinpirole and eticlopride. Putative DA neurons were inhibited by the D2-type receptor agonist quinpirole and returned to near-baseline firing rates or higher following the D2-type receptor antagonist eticlopride. Other unit types showed different responses to these D2-type receptor drugs. A multidimensional comparison of neural properties indicated that these subgroups often clustered independently of each other with minimal overlap. Firing pattern variability reliably distinguished putative DA neurons from other unit types. A combination of phasic burst properties and a low skew in the interspike interval distribution produced a neural population that was comparable to the one sorted by D2 pharmacology. These findings provide a quantitative statistical approach for the classification of VTA neurons in unanesthetized animals.
authors.affiliation: Center on Addiction, Learning, Memory, Department of Neuroscience, Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: William M
authors.initials: WM
authors.lastname: Doyon
authors.forename: John A
authors.initials: JA
authors.lastname: Dani
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D019257:Quinpirole / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D012457:Salicylamides / Q000494:pharmacology; D017557:Ventral Tegmental Area / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D018491:Dopamine Agonists; D018492:Dopamine Antagonists; D012457:Salicylamides; D019257:Quinpirole; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid; C045989:eticlopride; D004298:Dopamine