Ps. Chowdhury et al., EXOCYTOSIS FROM A SINGLE-RAT CHROMAFFIN CELL BY CHOLINERGIC AND PEPTIDERGIC NEUROTRANSMITTERS, Neuroscience, 59(1), 1994, pp. 1-5
Secretion of catecholamines from chromaffin cells is mediated by choli
nergic and peptidergic neurotransmitters.(3,11,14) The cholinergic tra
nsmitter acetylcholine activates both nicotinic and muscarinic recepto
rs to trigger catecholamine secretion in rat adrenal medulla.(17) Vaso
active intestinal polypeptide (VIP) has been identified as the peptide
rgic transmitter in rat adrenal medulla and may also be the non-cholin
ergic transmitter in bovine adrenal.(18,23) Pituitary adenylate cyclas
e activating polypeptide (PACAP), a VIP-like secretin peptide, is also
found in the adrenal,(5) and is a potent secretagogue.(7,21) Thus, PA
CAP may be another peptidergic transmitter at the adrenal synapse.(19)
A most intriguing property of rat chromaffin cells is that stimulatio
n of nicotinic, muscarinic, VIP or PACAP receptors are each able to pr
oduce robust catecholamine secretion on their own.(11-13,21) This rais
es the question of whether a single chromaffin cell can respond to eac
h of the above agonists or whether the secretion is due to subpopulati
ons of chromaffin cells. This issue was addressed by using electrochem
ical techniques to monitor exocytosis from individual chromaffin cells
in culture.(2,9,22) We demonstrate that acetylcholine, nicotine, musc
arine, VIP and PACAP are each able to evoke catecholamine secretion fr
om a single chromaffin cell. Some cells only responded to acetylcholin
e. Furthermore, each agonist produced a distinct pattern of exocytosis
. Muscarine-evoked secretion exhibited a latency of 0.5-2 s, but exocy
tosis persisted up to 30 s following 500 ms stimulation. Nicotine prod
uced an immediate response which usually ended within 10 s. The secret
ory pattern following acetylcholine appeared to be the sum of the nico
tinic and muscarinic patterns, showing both rapid onset and longer dur
ation. The unique property of peptidergic stimulation was that a brief
exposure caused exocytosis to persist for up to 2 min. Like muscarine
, peptides exhibited latency in producing exocytosis. These findings s
upport the idea that the interactive control of catecholamine secretio
n by nicotinic, muscarinic and peptidergic receptors occurs at the lev
el of single cells.