Release of [14C]quinacrine from peripheral and central nerves

Incubations of intestinal mouse smooth muscle sheets including Auerbach's plexus and slices of the spinal cord in buffer containing low concentrations of labelled quinacrine ([14C]QC) result in a high affinity binding of QC to certain nerve fibres. Various means of depolarization, such as veratridine, high potassium and electrical field stimulation, were used to assess quantitatively the release of QC from nerves. Under optimal release conditions, all 3 types of depolarizations induced a clearcut increase in radioactivity of a continuously superfused buffer. When intestinal muscle sheets were incubated in high concentrations of QC (5 . 10(-6)--5 . 10(-5) M) the depolarization-induced release was blocked. Similarly, high concentrations of QC (10(-5) M) blocked release of [3H]noradrenaline from adrenergic nerves. Low QC concentrations did not affect the depolarization induced release of [3H]noradrenaline from adrenergic nerves but caused a moderately increased spontaneous overflow of noradrenaline. The present data, together with previous studies, permit the conclusion that QC in low concentrations can be used to label selectively a population of non-adrenergic nerve fibres. This binding is closely related to the transmitter storage and release mechanisms and can be used to study the activity of such nerves.