The Journal of Neuroscience, February 15, 2001, 21(4):1393-1400
Stimulation of Nitric Oxide-cGMP Pathway Excites Striatal
Cholinergic Interneurons via Protein Kinase G Activation
Diego
Centonze1, 2,
Antonio
Pisani1, 2,
Paola
Bonsi2,
Patrizia
Giacomini3,
Giorgio
Bernardi1, 2, and
Paolo
Calabresi1, 2
1 Clinica Neurologica, Dipartimento di Neuroscienze,
Università "Tor Vergata," 00133 Rome, Italy,
2 Istituto di Ricovero e Cura a Carattere Scientifico,
Fondazione Santa Lucia, 00179 Rome, Italy, and 3 Il
Clinica Neurologica, Università "La Sapienza," 00185 Rome,
Italy
Conflicting data have been collected so far on the action of nitric
oxide (NO) on cholinergic interneurons of the striatum. In the present
in vitro electrophysiological study, we reported that
intracellularly recorded striatal cholinergic interneurons are excited
by both hydroxylamine and
S-nitroso-N-acetylpenicillamine, two NO donors. This excitation persisted unchanged in the presence of
glutamate, dopamine, and substance P receptor antagonists as well as
after blockade of tetrodotoxin (TTX)- and calcium channel-sensitive transmitter release, suggesting that NO produces its effects by modulating directly resting ion conductances in the somatodendritic region of striatal cholinergic cells. The depolarizing effect of
hydroxylamine was greatly reduced by lowering external concentrations of sodium ions (from 126 to 38 mM) and did not reverse
polarity in the voltage range from
120 to
40 mV. The sodium
transporter blockers bepridil and 3',4'-dichlorobenzamil were
conversely ineffective in preventing NO-induced membrane
depolarization. Intracellular cGMP elevation is required for the action
of hydroxylamine on striatal cholinergic cells, as demonstrated by the
findings that the membrane depolarization produced by this
pharmacological agent was prevented by bath and intracellular
application of two inhibitors of soluble guanylyl cyclase and was
mimicked and occluded by zaprinast, a cGMP phosphodiesterase inhibitor.
Finally, intracellular Rp-8-Br-cGMPS, a protein kinase G (PKG)
inhibitor, blocked the hydroxylamine-induced membrane depolarization of
cholinergic interneurons, whereas both okadaic acid and calyculin A,
two protein phosphatase inhibitors, enhanced it, indicating that
intracellular PKG and phosphatases oppositely regulate the sensitivity
of striatal cholinergic interneurons to NO. The characterization of the
cellular mechanisms involved in the regulation of striatal interneuron
activity is a key step for the understanding of the role of these cells
in striatal microcircuitry.
Key words:
acetylcholine; basal ganglia; brain slices; intracellular recordings; NOS-positive interneurons; protein
phosphatases
Copyright © 2001 Society for Neuroscience 0270-6474/01/2141393-08$05.00/0