Effect of substance P on catecholamine secretion from rat adrenal medulla in situ

Splanchnic nerve stimulation caused a frequency-dependent increase in catecholamine (CA) secretion with a maximum at 10 Hz from adrenal medulla of WKY rats in situ. Substance P (SP(1-11)) had no effect on the basal output of CA. During nerve stimulation, however, SP(1-11) decreased only the adrenaline (A) secretion by 18% at 10 Hz and by 55% at 20 Hz (p less than 0.05), whereas the noradrenaline (NA) secretion remained unchanged. These results provide further evidence that SP(1-11) may modulate frequency-dependently the secretion of CA from adrenal medulla in situ.