Interactions of catecholamine uptake inhibitors and norepinephrine on autonomic ganglia

The effect of catecholamine uptake inhibitors on blockade by norepinephrine was observed in the isolated stellate ganglion of the hamster. The preganglionic nerve was stimulated, supramaximally, at 0.2 Hz and compound action potentials were recorded from the postganglionic nerve. Norepinephrine blocked ganglionic transmission. The sensitivity of the ganglion to norepinephrine was increased by the catecholamine uptake inhibitors, desipramine (3 X 10(-7) M), d-amphetamine (10(-6) and 10(-5) M) and tyramine (10(-4) M). Ouabain (10(-5) and 3 X 10(-5) M) did not change the sensitivity of the ganglion to norepinephrine. All the drugs reduced the uptake by the [3H]norepinephrine into the ganglion. The inhibition of [3H]norepinephrine uptake by the drugs could be correlated with the increase in sensitivity of the ganglion to norepinephrine. These results support the hypothesis that catecholamine uptake is important in terminating the actions of exogenously applied norepinephrine, and that inhibition of the catecholamine uptake increases the sensitivity of the ganglion to norepinephrine.