Progressive and lasting amplification of accumbal nicotine-seeking neural signals.
Journal of Neuroscience. 2010-01-06; 30(1): 276-286
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1. J Neurosci. 2010 Jan 6;30(1):276-86. doi: 10.1523/JNEUROSCI.2820-09.2010.
Progressive and lasting amplification of accumbal nicotine-seeking neural
Guillem K(1), Peoples LL.
(1)Department of Integrative Neurophysiology, Center for Neurogenomics and
Cognitive Research, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands.
Although neuroadaptations in the nucleus accumbens (NAc) are thought to
contribute to nicotine addiction, little is known about the chronic effects of
nicotine on NAc neuronal activity. In the present experiment, rats were exposed
to a 23 d period of nicotine self-administration (SA), a 30 d abstinence period,
and a 7 d period of reexposure to SA. Chronic electrophysiological procedures
were used to record the activity of individual NAc neurons on the 3rd and 23rd
days of initial SA and on the 1st, 3rd, and 7th days of reexposure.
Between-session comparisons showed that NAc neurons exhibit two patterns of
plasticity under the present experimental conditions. First, phasic-increase
firing patterns time-locked to the nicotine-reinforced lever press do not change
during initial SA, but then show increases in prevalence and amplitude after
abstinence, which persist during reexposure. Second, for neurons that show no
phasic response time-locked to the nicotine-reinforced lever press, average
baseline and SA firing rates decrease during initial SA, return to normal during
abstinence, and decrease again during reexposure. As a combined consequence of
the two types of neurophysiological plasticity, average firing rate of NAc
neurons at the time of nicotine-directed behavior undergoes a progressive and
persistent net amplification, across the successive stages of SA, abstinence, and
reexposure. This net increase in NAc firing at the time of nicotine-directed
behavior occurs in association with an increase in animals’ motivation to seek
nicotine. The adaptations that occur in nicotine-exposed animals do not occur in
animals exposed to sucrose. The NAc neurophysiological plasticity potentially
contributes to compulsive tobacco use.
PMID: 20053909 [Indexed for MEDLINE]