Lesions of the lateral parabrachial nucleus block the aversive motivational effects of both morphine and morphine withdrawal but spare morphine's discriminative properties.
ABSTRACT This study examined if the aversive properties of morphine, the aversive properties of morphine withdrawal, and the discriminative properties of morphine are mediated by common neurobiological substrates. Lesions of the lateral parabrachial nucleus, which blocked the aversive properties of morphine in the conditioned taste aversion paradigm, also blocked the acquisition of conditioned place aversions to environments paired with the aversive properties of morphine withdrawal in morphine-dependent rats. When morphine and saline were used as cues in a discrimination task, however, both sham-operated and lesioned rats were able to solve the task.
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ABSTRACT: The lateral parabrachial complex has been related to various emotional-affective processes. It has been shown that electrical stimulation of the external lateral parabrachial (LPBe) nucleus can induce reinforcing effects in place preference and taste discrimination tasks but does not appear to support self-stimulation. This study examined the relative relevance of place and taste stimuli after electrical stimulation of the LPBe nucleus. A learning discrimination task was conducted that simultaneously included both sensory indexes (taste and place) in order to determine the preference of animals for one or the other. After a taste stimulus reversal task, the rewarding effect of stimulation was found to be preferentially associated with place. These results are discussed in the context of the rewarding action and biological constraints induced by different natural and artificial reinforcing agents.Neurobiology of Learning and Memory 01/2013; · 3.33 Impact Factor
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ABSTRACT: Orexin (or hypocretin) is synthesized exclusively in dorsomedial, perifornical, and lateral hypothalamus (LH). These neurons are implicated in several functions, including reward processing. We examined the ventral tegmental area (VTA) as a possible site of orexin action for drug preference during protracted morphine abstinence, and studied functional topography of orexin projections to VTA. Male Sprague Dawley rats were used to investigate whether orexin cells that project to VTA exhibit Fos activation with morphine conditioned place preference (CPP), and whether these cells exhibit increased Fos with morphine CPP during protracted abstinence. Unilateral injections of a retrograde tracer (WGA-Au, 350-400 nl) were made into the VTA or a nonreward area, locus ceruleus, and morphine or placebo pellets were implanted for 14 d. Approximately 2 weeks after pellet removal (post dependence), CPP conditioning and testing were conducted. Triple labeling for WGA-Au, Fos, and orexin revealed that the percentage of VTA-projecting orexin neurons Fos activated on the CPP test day significantly increased in post-dependent (vs nondependent) rats, and was exclusive to LH orexin neurons (not dorsomedial or perifornical). Post-dependent animals showed a positive correlation between CPP scores and percentages of Fos-activated, caudal VTA-projecting LH orexin cells. Unlike afferents to caudal VTA, percentages of rostral VTA-projecting, LH orexin cells that were Fos activated showed a positive correlation with CPP only in nondependent animals. Fos in LC-projecting orexin cells was not correlated with CPP in any group. These results indicate that VTA is a heterogeneous and functionally significant target of orexin neurons for morphine reward during protracted abstinence.Journal of Neuroscience 03/2012; 32(11):3809-17. · 6.91 Impact Factor
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ABSTRACT: The insular cortex has been related to various sensory, regulatory, and learning processes, which frequently include affective-emotional components. The objective of this study was to investigate the possibility of inducing reinforcing effects by electrical stimulation of this cortical region in Wistar rats. Concurrent conditioned place preference tasks were conducted for this purpose, using two rectangular mazes that differed in dimensions, texture, and spatial orientation. A significant correlation was found in the preferences induced by insular cortex electrical stimulation between the two mazes. Animals showed consistent preference or avoidance behaviors associated with simultaneous insular cortex stimulation. No electrical self-stimulation was achieved. In a second experiment, animals that showed consistent place preference after the simultaneous insular cortex electrical stimulation were administered with 4 mg/ml/kg of naloxone. The results revealed that this opiate antagonist blocked concurrent place preference learning when the task was conducted in a new maze but not when it was conducted in the same maze as that in which the animals had learned the task. These results are discussed in terms of the participation of the insular cortex in various reward and aversion modalities.Experimental Brain Research 02/2013; · 2.22 Impact Factor