Two types of neurone in the rat ventral tegmental area and their synaptic inputs

Steven Johnson, R. A. North

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Abstract

1. Intracellular recordings were made from 241 ventral tegmental neurones in slices of rat midbrain. Seventy-seven per cent of neurones were hyperpolarized by dopamine (principal cells); 16% were hyperpolarized by opioid peptides (secondary cells). 2. Most principal cells fired spontaneously (1-3 Hz) with a threshold of -53 mV; most secondary cells did not fire spontaneously. Action potentials of principal cells were longer (0.9 ms) than those of secondary cells (0.5 ms). 3. Focal electrical stimulation within the ventral tegmental area evoked a biphasic synaptic potential, depolarization followed by hyperpolarization, with a duration of about 200 ms. Experiments with receptor antagonists showed that the depolarizing component resulted from activation of both N-methyl-D-aspartate (NMDA) and non-NMDA receptors and the hyperpolarizing component resulted from activation of GABA(A) receptors. 4. A later hyperpolarizing synaptic potential developed after a latency of 50 ms, reached its peak in 250 ms and had a duration of about 1 s. It reversed polarity at -108 mV (external potassium concentration was 2.5 mM), was blocked by phaclofen (30 μM-1 mM) or 2-hydroxysaclofen (100-300 μM). In some cells, a phaclofen-resistant component remained that was increased by cocaine and blocked by sulpiride (1 μM). 5. It is concluded that the ventral tegmental area contains two types of neurone having properties similar to those in the substantia nigra. The cells receive synaptic inputs mediated by excitatory amino acids acting at NMDA and non-NMDA receptors, GABA acting at GABA(A) and GABA(B) receptors, and dopamine acting at D2 receptors.

Original languageEnglish (US)
Pages (from-to)455-468
Number of pages14
JournalJournal of Physiology
Volume450
StatePublished - 1992

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Ventral Tegmental Area
Neurons
D-Aspartic Acid
Synaptic Potentials
N-Methylaspartate
gamma-Aminobutyric Acid
Dopamine
GABA-B Receptors
Sulpiride
Excitatory Amino Acids
Opioid Peptides
Substantia Nigra
GABA-A Receptors
Mesencephalon
Cocaine
Electric Stimulation
Action Potentials
Potassium

ASJC Scopus subject areas

  • Physiology

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Two types of neurone in the rat ventral tegmental area and their synaptic inputs. / Johnson, Steven; North, R. A.

In: Journal of Physiology, Vol. 450, 1992, p. 455-468.

Research output: Contribution to journalArticle

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