Inhibition of [3H]norepinephrine uptake in organ cultured rat superior cervical ganglia by xylamine.

The superior cervical ganglia (SCG) of the rat, when maintained in organ culture, show an increase in [3H]norepinephrine (NE) uptake in the first 2 days and then a leveling off of this activity through 6 days of culture. The [3H]NE uptake in cultured SCG is Na+ - and temperature-dependent and is inhibited by cocaine, desipramine and benztropine with potencies similar to those reported for uptake inhibition into noradrenergic nerve terminals. The preparation also accumulates [3H]dopamine (DA), but, in contrast to NE and DA uptake in the brain, desipramine and benztropine show no specificity for a particular catecholamine, inhibiting both [3H]NE and [3H]DA uptake with potencies similar to those shown for NE uptake in brain. Thus, observed DA uptake and SCG appears to occur mostly via the NE uptake system, not a specific DA uptake system. Xylamine (N-2-chloroethyl-N-ethyl-2-methylbenzylamine) at 10 microM irreversibly inhibits [3H]NE uptake in cultured SCG by 85% in 30 min, uptake being measured after washing away unbound drug. The IC50 for inhibition is about 0.3 microM. When SCG are again cultured after xylamine exposure, [3H]NE uptake recovers after 2 days. This recovery is partially blocked by cycloheximide, indicating that the synthesis of new uptake sites may be involved.