3,4-Diaminopyridine facilitates norepinephrine release in chick sympathetic neurons.
OBJECTIVE
To study the mechanism by which 3,4-diaminopyridine (DAP) facilitates electrically evoked [3H]norepinephrine ([3H]NE) release in sympathetic neurons from chick embryos.


METHODS
The neurons were incubated with [3H]NE or Fura-2. [3H]NE) release or [Ca2+]i was determined.


RESULTS
The electrically evoked [3H]NE release and the elevation of [Ca2+]i were inhibited completely by sodium channel blocker tetrodotoxin (TTX), strongly by the antagonist of N-type calcium channel omega-conotoxin GVIA (CTX), and slightly by the antagonist of L-type calcium channel (-)isradipine, but enhanced by the agonist of L-type calcium channel Bay k 8644. In the presence of DAP, the electrically evoked [3H]NE release and [Ca2+]i were facilitated, the inhibition of [3H]NE release and [Ca2+]i by CTX was attenuated, but that by (-)isradipine was enhanced, and Bay k 8644 was no longer effective.


CONCLUSIONS
In the cultured chick sympathetic neurons DAP facilitates electrically evoked [3H]NE release mediated by enhancement of influx of external Ca2+ through the L-type Ca2+ channel.
Huang
H Y
HY
Shanghai Institute of Physiology, Chinese Academy of Science.
Zhou
C W
CW
D015761:4-Aminopyridine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000077770:Amifampridine; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D002642:Chick Embryo; D005728:Ganglia, Sympathetic / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D010455:Peptides; D013779:Tetrodotoxin; D020866:omega-Conotoxin GVIA; D015761:4-Aminopyridine; D000077770:Amifampridine; D009638:Norepinephrine