Depolarization-induced release of [(3)H]histamine by high potassium concentrations, electrical stimulation and veratrine from rat brain slices after incubation with the radiolabelled amine.
Brain slices obtained from neocortex, hypothalamus or hippocampus were incubated with [(3)H]histamine and subsequently superfused and exposed to different depolarizing stimuli, viz. high K(+)-concentrations, electrical field stimulation and veratrine. K(+)-induced release of tritium was completely calcium-dependent and its magnitude depended on the K(+)-concentration, with maximal release being reached at 56 mM K(+). Electrically-evoked release of tritium increased with increasing frequencies and reached its maximum at about 20 Hz. The electrically-evoked release appeared to be totally calcium-dependent and it was strongly inhibited by tetrodotoxin. Veratrine (5-100 ?M) also induced a release of tritium; maximal release was obtained at 100 ?M veratrine. Veratrine-induced release was partially calcium-dependent and was strongly reduced by tetrodotoxin. Taken together the data indicate that the depolarization-induced release of tritium from brain slices pre-labelled with [(3)H]histamine, represents [(3)H]histamine release from neurons and not from either mast cells or glial cells. It remains to be established whether these neurons are specifically histaminergic.
Mulder
A H
AH
Department of Pharmacology, Free University, Medical Faculty Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.
van Amsterdam
R G
RG
Wilbrink
M
M
Schoffelmeer
A N
AN