The release and clearance of electrically evoked catecholamine (CA) in the ventral portion of the bed nucleus of the stria terminalis (BSTV) in mouse brain slices was evaluated with fast-scan cyclic voltammetry at carbon-fiber microelectrodes (CFME). Uptake in this region was observed to be markedly slower than in the caudate putamen (CPu). Clearance rates were reduced in the BSTV in both norepinephrine transporter knockout (NET KO) and dopamine transporter knockout (DAT KO) mice when compared to results in wild-type (WT) mice. However, uptake was faster in the BSTV in both the DAT and NET KO mice than in the CPu of DAT KO mice. This indicates that both transporters play a role in CA clearance in the BSTV. The transporters restrict extracellular CA to the general area of the BSTV, as revealed by the diminished signal as the CFME is moved sequentially further and further from the site where CA release is evoked. However, in slices from the DAT KOs and NET KOs, CA release could be observed outside of the BSTV region during such experiments. These results show that the low rate uptake in the BSTV facilitates extrasynaptic diffusion of catecholamine, but that uptake still regulates and limits the range of the transmitter to the region. Slower clearance from the extracellular fluid allows the released CA to act as a volume transmitter and diffuse to distant sites within the region to exert its neurochemical action.
Copyright 2002 Wiley-Liss, Inc.