Reserpine-induced catecholamine depletion from small cells in rat sympathetic ganglia

Two reserpine dosage schedules were applied to Wistar rats (a) 5 mg/kg i.p. 6 hr before sacrifice and (b) 5 mg/kg i.p. at 36, 24 and 12 hr prior to sacrifice. Control animals were correspondingly sham-injected. The coeliac-mesenteric ganglion complex was removed and processed either for the Falck-Hillarp fluorescence histochemical technique or fixed in glutaraldehyde followed by 3.5% potassium dichromate for a chromaffin-type reaction. After a single reserpine injection there was a statistically significant (p less than 0.001) reduction in the percentage of 'chromaffin-positive' cells and a statistically significant (p less than 0.001) increase in the percentage of 'chromaffin-negative' cells compared with controls. No obvious reduction in fluorophore emission from small intensely fluorescent (SIF) cells was observed. After prolonged reserpinization (3 x 5 mg/kg) there was a highly significant reduction in the percentage of 'chromaffin-positive' small cells and also a significantly lower (by a factor of 2) level of fluorescent emission from SIF cells. The catecholamine-releasing potential of small cells is demonstrated by these results.