Release of endogenous norepinephrine and dopamine from rat brain regions in vitro

Using radioenzymatic assay procedures, we have measured picomolar amounts of endogenous norepinephrine (NE) and dopamine (DA) released $\text{in vitro}$. The release of NE and DA in response to KCl stimulation was examined in 6 brain regions: cortex, hippocampus, hypothalamus, striatum, combined accumbens-olfactory tubercle, and substantia nigra. NE release was detectable in all regions except striatum. Amounts of NE released by 55mM KCl (expressed as % control) were: cortex (313%), hippocampus (227%), hypothalamus (225%), accumbens-tubercle (278%), s. nigra (155%). KCl stimulated release of DA was detected in 3 regions: striatum (414%), accumbenstubercle (282%), and hypothalamus (312%). DA was measurable in filtrates from the s. nigra but levels in control and KCl stimulated samples were equal. Release of NE and DA was also measured in 12 brain regions after incubation of tissue $\text{in vitro}$ with 10^?4M d-amphetamine sulfate. d-Amphetamine stimulated NE outflow when compared to controls in all regions examined. DA outflow was markedly increased in most regions, especially striatum (287%), hypothalamus (387%) and accumbens-tubercle (670%). d-Amphetamine doubled endogenous DA outflow from the s. nigra.