Behavioral neuroscience
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Behavioral neuroscience · Dec 2006
The human mu-opioid receptor gene polymorphism 118A > G decreases cortical activation in response to specific nociceptive stimulation.
The authors sought to investigate the role of a common single nucleotide polymorphism in the mu-opioid receptor gene (OPRM1) 118A > G for nociceptive sensory processing using event-related potentials (ERPs). Specific nociceptive (carbon dioxide [CO-sub-2]: 40% volume-to-volume [vol/vol] and 60% vol/vol) and nonnociceptive (hydrogen sulfide, 2 parts per million [ppm] and 4 ppm) stimuli were applied to the nasal mucosa of 45 volunteers. ERPs were recorded from a central lead. ⋯ In discriminant analysis, ERP amplitude N1 response to the weaker nociceptive stimuli was the only ERP parameter that discriminated statistically significantly between carriers and noncarriers of the variant 118G allele. On the basis of N1-CO-sub-2 (40% vol/vol), the authors correctly backclassified 68.6% of the cases as carriers or noncarriers of the allele. The OPRM1 118A > G polymorphism specifically modulates nociceptive but not nonnociceptive cortical activation.
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Behavioral neuroscience · Apr 2006
Comparative StudyInactivation of sodium channel Scn8A (Na-sub(v)1.6) in Purkinje neurons impairs learning in Morris water maze and delay but not trace eyeblink classical conditioning.
To examine the isolated effects of altered currents in cerebellar Purkinje neurons, the authors used Scn8a-super(flox/flox), Purkinje cell protein-CRE (Pcp-CRE) mice in which Exon 1 of Scn8a is deleted only in Purkinje neurons. Twenty male Purkinje Scn8a knockout (PKJ Scn8a KO) mice and 20 male littermates were tested on the Morris water maze (MWM). ⋯ PKJ Scn8a KO mice were impaired in delay conditioning and MWM but not in trace conditioning. These results provide additional support for the necessary participation of cerebellar cortex in normal acquisition of delay eyeblink conditioning and MWM and raise questions about the role, if any, of cerebellar cortex in trace eyeblink conditioning.
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Behavioral neuroscience · Feb 2006
Differential involvement of enkephalins in analgesic tolerance, locomotor sensitization, and conditioned place preference induced by morphine.
In this study, the authors investigated the role of enkephalins in morphine-induced conditioned place preference, locomotor sensitization, and analgesic tolerance. Both preproenkephalin wild type (ppENK [+/+]) and knockout (ppENK [-/-]) mice showed similar preference for the morphine-paired chamber over the vehicle-paired chamber, indicating morphine induced comparable conditioned place preference in ppENK (+/+) and ppENK (-/-) mice. ⋯ However, as shown previously, ppENK (-/-) mice displayed blunted morphine analgesic tolerance. Taken together, the results suggest that enkephalins may be important for the development of analgesic tolerance but not for conditioned place preference or behavioral sensitization induced by morphine.
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Behavioral neuroscience · Dec 2003
Comparative StudyOpioid receptors regulate the extinction of Pavlovian fear conditioning.
Rats received a single pairing of an auditory conditioned stimulus (CS) with a footshock unconditioned stimulus (US). The fear (freezing) that had accrued to the CS was then extinguished. ⋯ Finally, an injection of naloxone on test failed to reinstate extinguished responding that had already accrued to the CS. These experiments show that opioid receptors regulate the development, but not the expression, of fear extinction and are discussed with reference to the roles of opioid receptors in US processing, memory, and appetitive motivation.
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Behavioral neuroscience · Oct 2002
Comparative StudyFlavor avoidance induced by LiCl and dexfenfluramine in rats and mice using nondeprivation protocols.
Using dexfenfluramine as unconditional stimulus (US), the authors confirmed that sham-operated and area postrema (AP)-lesioned rats form comparable conditioned flavor avoidances. When lithium chloride (LiCI) was used as the US, AP-lesioned rats did not learn to avoid a drug-paired flavor conditional stimulus (CS+). ⋯ When flavored gels of Polycose were used as CSs, C57BL/6J mice developed flavor avoidance with either LiCl or dexfenfluramine as US. Compared with rats, mice required higher doses of these agents, avoidance was not complete after many pairings, and there was no generalization to the CS-.