Effects of cortical and striatal dopamine D1 receptor blockade on cued versus noncued behavioral responses.

Various lines of evidence suggest that disruptions in brain dopamine (DA) transmission produce behavioral impairments that can be overcome by salient response-eliciting environmental stimuli. We examined here whether D1 receptor blockade within striatal or frontal cortical DA target regions would differentially affect head entry responses elicited by an auditory cue compared with those occurring during noncued intertrial intervals. Rats received 2 drug-free 28-trial daily sessions in which an auditory cue was immediately followed by food delivery. On the following day, separate groups of rats received bilateral infusions of D1 antagonist SCH23390 to the dorsomedial striatum (DMS), nucleus accumbens (NAcc) core, or the medial prefrontal cortex (mPFC). SCH23390 infused into the DMS and NAcc core suppressed noncued head entries but had no effect on head entries in response to the auditory cue. SCH23390 infused to the mPFC did not reduce either cued or noncued approach responses. Systemic administration of the drug, in contrast, reduced the frequency of both cued and noncued approaches. The results are consistent with the notion that has emerged from the Parkinson's literature that reduced DA transmission produces behavioral suppression that can be overcome by salient environmental response elicitors, and extends this notion by showing that D1 receptor transmission within the striatum strongly suppresses noncued responses while leaving the identical behavior intact when cued by an environmental stimulus. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Effects of hippocampal N-methyl-[D]-aspartate infusion on locomotor activity and prepulse inhibition: Differences between the dorsal and ventral hippocampus.

Prepulse inhibition (PPI) of the acoustic startle response and open-field locomotor activity were measured after bilateral infusion of N-methyl-[D]-aspartate into the ventral (0.10, 0.25, 0.50 Ag/side) and dorsal (0.10, 0.25, 0.50, 0.70 wg/side) hippocampus of Wistar rats. Dose-dependent hyperactivity and disruption of PPI-behavioral effects related to psychotic symptoms-were observed after ventral infusions but were virtually absent after dorsal infusions. This functional dorsal-ventral difference might be related to the different connections of the dorsal and ventral hippocampus with the amygdala, nucleus accumbens, and prefrontal cortex, which have been implicated in the regulation of locomotor activity and PPI. Hippocampal overactivity has been associated with schizophrenia. The findings suggest that overstimulation of the ventral hippocampal projections may contribute to behavioral outcomes related to psychotic symptoms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of D1 or D2 dopamine receptor antagonism in the medial preoptic area, ventral pallidum, or nucleus accumbens on the maternal retrieval response and other aspects of maternal behavior in rats.

The medial preoptic area (MPOA), ventral pallidum (VP), and nucleus accumbens (NA) receive dopaminergic afferents and are involved in maternal behavior. Experiments investigated whether dopamine (DA) receptor antagonism in NA disrupts maternal behavior, determined the type of DA receptor involved, and investigated the involvement of drug spread to VP or MPOA. Injection of SCH 23390 (D1 DA receptor antagonist) into NA of postpartum rats disrupted retrieving at dosage levels that were ineffective when injected into MPOA or VP. Motor impairment was not the cause of the deficit. Injection of eticlopride (D2 DA receptor antagonist) into NA or VP was without effect. Results emphasize the importance of DA action on D1 receptors in NA for retrieval behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Response rate and sensitivity to the molar feedback function relating response and reinforcement rate on VI+ schedules of reinforcement.

In 5 experiments, the author examined rats' sensitivity to the molar feedback function relating response rate to reinforcement rate on schedules of reinforcement. These studies demonstrated that, at lower rates of responding, rats' performance on variable ratio (VR), variable interval (VI), and variable interval with linear feedback loop (VI+) schedules was determined largely by reinforcement of interresponse times; response rates were faster on VR than on both VI and VI+ schedules. In contrast, when procedures were adopted to maintain high rates of response, rats showed sensitivity to the molar characteristics of the schedules; they responded as fast on a VI+ schedule as on a VR schedule and faster on both of these schedules than on a yoked VI schedule. When the variance of response rate was manipulated, this factor was noted as an important element in determining sensitivity to the molar characteristics of the schedule. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of aging, distraction, and response pressure on the binding of actors and actions.

Two experiments provide evidence for an age-related deficit in the binding of actors with actions that is distinct from binding deficits associated with distraction or response pressure. Young and older adults viewed a series of actors performing different actions. Participants returned 1 week later for a recognition test. Older adults were more likely than young adults to falsely recognize novel conjunctions of familiar actors and actions. This age-related binding deficit occurred even when older adults could discriminate old items from new items just as well as could young adults. Young adults who experienced distraction or time pressure also had difficulty discriminating old items from conjunction items, but this deficit was accompanied by a deficit at discriminating old and new items. These results suggest that distraction and response pressure lead to deficits in memory for stimulus components, with any deficits in binding ability commensurate with these deficits in component memory. Aging, in turn, may lead to binding difficulties that are independent of attention-demanding executive processes involved in maintaining individual stimulus components in working memory, likely reflecting declines in hippocampally mediated associative processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of experimenter modeling, demands for honesty, and initial level of suggestibility on response to "hypnotic" suggestions.

Pretested 180 college students on behavioral (objective) and experiential (subjective) responses to the test suggestions of the Barber Suggestibility Scale. After being exposed to 1 of 3 treatments--E modeling, hypnotic induction, or control--each S was retested on the same scale. Strong demands to give honest experiential reports were administered to 1/2 of the Ss under each treatment. Ss who were exposed to E modeling manifested a greater enhancement in objective responsiveness to test suggestions than control Ss and as much enhancement as Ss who were exposed to hypnotic induction. E modeling was as effective as hypnotic induction in enhancing sujective responsiveness to test suggestions with and without demands for honest reports. Under both the E modeling and hypnotic induction treatments, Ss who had initially manifested a high level of suggestibility (pretest) showed as much enhancement in subjective responsiveness to test suggestions as medium- or low-suggestible Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temperature and activity responses to sucrose concentration reductions occur on the 1st but not the 2nd day of concentration shifts, and are blocked by low, constant glucocorticoids.

Previous findings (N. Pecoraro, J. Chou-Green, & M. F. Dallman, 2003; N. Pecoraro & M. F. Dallman, 2005) indicated that unexpected reductions in sucrose concentration in once daily meals result in a febrile response on the 1st, but not the 2nd day of a concentration shift. This study shows that this day-specific fever is blocked by adrenalectomy accompanied by constant low corticosterone replacement. Rats implanted with telemetry probes were adrenalectomized and given low-corticosterone pellets or were sham operated. Food-restricted rats were given 2 rounds of sucrose concentration downshifts, as follows: 32% sucrose (14 days), 4% sucrose (6 days), 32% sucrose (4 days), and 4% sucrose (4 days). Intact rats showed more pronounced anticipation of the sucrose than did rats having low, clamped corticosterone. Only intact rats showed a 4-hr, postshift temperature burst on the 1st, but not the 2nd day of the shift to 4% sucrose, during both rounds of shifting. Increased activity accompanied the fever. These data confirm previous findings, show them to be dependent on high corticosterone, and appear to be related to a host of day-specific alterations in other motor outflows following unexpected downward shifts in palatable sucrose concentrations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)