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Behavioral/Systems/Cognitive Adrenergic and Noradrenergic Innervation of the Midbrain

Summary: Behavioral/Systems/Cognitive
Adrenergic and Noradrenergic Innervation of the Midbrain
Ventral Tegmental Area and Retrorubral Field: Prominent
Inputs from Medullary Homeostatic Centers
Carlos A. Mejías-Aponte,1 Candice Drouin,2 and Gary Aston-Jones3
1Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129, 2Department of Psychiatry,
University of Pennsylvania, Philadelphia, Pennsylvania 19104-6100, and 3Department of Neurosciences, Medical University of South Carolina, Charleston,
South Carolina 29425
Adrenergic agents modulate the activity of midbrain ventral tegmental area (VTA) neurons. However, the sources of noradrenergic and
adrenergic inputs are not well characterized. Immunostaining for dopamine -hydroxylase revealed fibers within dopamine (DA)
neuron areas, with the highest density in the retrorubral field (A8 cell group), followed by the VTA (A10 cell group), and very few fibers
within substantia nigra compacta. A less dense, but a similar pattern of fibers was also found for the epinephrine marker, phenylethano-
lamine N-methyl transferase. Injection of the retrograde tracer wheat germ agglutinin-apo (inactivated) horseradish peroxidase conju-
gated to colloidal gold, or cholera toxin subunit b, revealed that the noradrenergic innervation of the A10 and A8 regions arise primarily
from A1, A2, A5, and locus ceruleus neurons. Selective lesions of the ventral noradrenergic bundle confirmed a prominent innervation
from A1 and A2 areas. Retrogradely labeled epinephrine neurons were found mainly in the C1 area. The identification of medullary
noradrenergic and adrenergic afferents to DA neuron areas indicates new pathways for visceral-related inputs to reward-related areas in
the midbrain.
Midbrain dopamine (DA) and non-DA neurons in the ventral


Source: Aston-Jones, Gary - Department of Neurosciences, Medical University of South Carolina


Collections: Biology and Medicine