Nitric Oxide is used as an Orthograde Cotransmitter at Identified
Histaminergic Synapses.
Jacklet, Jon W.
Department of Biological Sciences, University at Albany, SUNY, Albany, NY
12222, tele: (518) 442-4373, FAX: (518) 442-4767, E-mail:
JWJ74@cnsvax.albany.edu.
APStracts 2:0149N, 1995.
SUMMARY AND CONCLUSIONS
1. Nitric oxide (NO) is produced by the enzyme nitric oxide synthase (NOS) and
serves as an interneuronal messenger. Here, an identified histaminergic neuron
(C2) in the mollusc Aplysia californica is shown to contain NOS using NADPH
diaphorase staining, suggesting that NO and histamine are used as
cotransmitters by neuron C2. 2. The NOS containing neuron, C2, evokes a very
slow excitatory postsynaptic potential in two of its identified postsynaptic
follower neurons that are insensitive to H1 and H2 histamine receptor
antagonists. 3. The very slow excitatory postsynaptic potential is blocked by
inhibitors of NOS, such as nitroarginine methyl ester, and suppressed by the
NO scavenger reduced hemoglobin. 4. Treatments with compounds that release
NO,such as nitrosocysteine, mimic the membrane depolarization and the decrease
in membrane conductance in the follower that are characteristic of the very
slow excitatory postsynaptic potential induced normally by the presynaptic C2
neuron. 5. These results indicate that NO is used as an orthograde synaptic
cotransmitter at synapses between histaminergicneuron C2 and its followers
that receive the very slow excitatory postsynaptic potential.
Received 12 April 1994; accepted in final form 9 May 1995.
APS Manuscript Number J-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.