Monitoring the release and uptake of catecholamines from terminals in weakl
y innervated brain regions is an important step in understanding their impo
rtance in normal brain function. To that end, we have labeled brain slices
from transgenic mice that synthesize placental alkaline phosphatase (PLAP)
on neurons containing tyrosine hydroxylase with antibody-fluorochrome conju
gate, PLAP-Cy5. Excitation of the fluorochrome enables catecholamine neuron
s to be visualized in living tissue. Immunohistochemical fluorescence with
antibodies to tyrosine hydroxylase and dopamine beta -hydroxylase revealed
that the PLAP labeling was specific to catecholamine neurons. In the prefro
ntal cortex (PFC), immunohistochemical fluorescence of the PLAP along with
staining for dopamine transporter (DAT) and norepinephrine transporter (NET
) revealed that all three exhibit remarkable spatial overlap. Fluorescence
from the PLAP antibody was used to position carbon-fiber microelectrodes ad
jacent to catecholamine neurons in the PFC. Following incubation with L-DOP
A, catecholamine release and subsequent uptake was measured and the effect
of uptake inhibitors examined. Release and uptake in NET and DAT knockout m
ice were also monitored. Uptake rates in the cingulate and prelimbic cortex
are so slow that catecholamines can exist in the extracellular fluid for s
ufficient time to travel similar to 100 mum. The results support heterologo
us uptake of catecholamines and volume transmission in the PFC of mice.