Cholinergic lesion of the striatum impairs acquisition and retention of a passive avoidance response.

Significant impairments in the acquisition and retention of a step-down passive avoidance task were found in Sprague-Dawley rats with striatal lesions induced by the cholinergic neurotoxin AF64A. No significant differences between control and AF64A-injected Ss were found in sensitivity to electric shock or in various measures of spontaneous locomotor activity. Striatal choline acetyltransferase (CAT) activity was significantly decreased in AF64A-treated Ss compared to controls, whereas glutamic acid decarboxylase (GAD) activities were not. Furthermore, there were no significant differences between groups in CAT and GAD in either the cortex or the hippocampus, supporting the specificity of the lesion to the striatum. The passive avoidance deficits support a role for the striatal cholinergic system in complex behavioral processes. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of hippocampectomy on the acquisition and recovery of a conditioned reflex to time in rats

The dynamics of time conditioning was studied before and after electrolytic lesions of the dorsal hippocampus in rats. Hippocampectomy disturbed the recovery of time conditioned reflex which was consolidated before surgery. The change depended on the extent of hippocampal lesion. In rats after the limited hippocampectomy the conditioned reflex recovered faster than in sham-operated animals. However, after more extensive lesions the process of conditioning recovery was delayed. In hippocampectomized animals without previous training the time conditioned reflex was not formed irrespective of the volume of brain lesion. Injection of amphetamine (0.05 mg/kg) was ineffective in this case.     

Age-related deficits in acquisition of a passive avoidance response.

In Exp. I, 80 male albino rats 10, 15, 20, 30, or 100 days old received a brief inescapable shock contingent upon making a step-off response. Step-off latencies increased for all age groups, but rate of learning was significantly faster in older Ss. Learning appeared to be based primarily upon punishment effects rather than general emotionality, since yoked Ss shocked after being placed directly on the grids did not acquire the avoidance response. Exp. II with 120 Ss employed 3 training conditions with independent groups 12, 15, 18, or 21 days old. The step-off response resulted in shock that was either: (a) escapable; (b) inescapable, 1-sec duration; or (c) inescapable, yoked duration. Younger Ss were again significantly inferior to more mature Ss. Escapable shock improved acquisition at 2 age levels, but the effect appeared to be more related to shock duration than to the response contingency. It is suggested that the requirement of withholding a punished response may represent a category of learning that is especially sensitive to maturational changes. (French summary) (16 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of blockade of the AMPA/kainate receptors of the nucleus accumbens on synaptic dopamine release during an emotional conditioned response

We studied the effect of combining prophylactic ondansetron (4 mg intravenously [IV]) to desflurane-based anesthesia in 90 ASA grade I or 11 women undergoing outpatient gynecological laparoscopy. Recovery after anesthesia, with special focus on postoperative nausea and vomiting (PONV), was assessed. Control groups received a similar desflurane anesthetic (placebo) or a propofol-infusion-based (active control) anesthetic. The study design was randomized, controlled, and double-blind (regarding ondansetron) and single-blind (regarding the anesthetic technique). Early recovery (eye opening, orientation, following commands, sitting) was similar in the three groups. However, overall home readiness (toleration of oral fluids, walking, pain tolerable by oral analgesics, no or only mild nausea) was achieved faster in the desflurane group receiving ondansetron (109 [21-937] min, P < 0.01) and in the propofol group (110 [33-642] min, P < 0.001) when compared to the desflurane only group (372 [45-723] min) (median [range]). The total incidence of PONV in the desflurane-only group was 80% (P < 0.01), compared to 40% and 20% in the desflurane group receiving ondansetron and the propofol group, respectively. The postoperative antiemetic requirements were consistently and significantly (P < 0.01) higher in the desflurane-only group compared to the other two groups. Postoperative sedation, analgesic requirements, and psychomotor recovery (assessed by the Maddox Wing and the Digit Symbol Substitution Tests) were similar in the three groups. Our results suggest that in order to achieve a propofol-like recovery profile in patients with a high likelihood of PONV, desflurane should be combined with a potent antiemetic (e.g., ondansetron).     

The effects of reserpine on the acquisition of the conditioned avoidance response.

"Six Macacus cynomolgus monkeys were trained in a shock-avoidance situation while under the influence of reserpine. Three sessions of 60 trials were given a week apart. Subsequent acquisition of the habit was retarded." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Antagonism by locally applied dopamine into the nucleus accumbens or the corpus striatum of alpha-methyltyrosine-induced disruption of conditioned avoidance behaviour

Male Sprague-Dawley rats were trained to avoid an electric shock in a two-way shuttle-box. The local application of dopamine into the nucleus accumbens or the corpus striatum was found to antagonize the suppression of conditioned avoidance behaviour induced by systemically administered alpha-methyltyrosine, emphasizing the importance of these dopamine-rich brain structures in mediating conditioned avoidance behaviour.     

Dissociations in dopamine release in medial prefrontal cortex and ventral striatum during the acquisition and extinction of classical aversive conditioning in the rat

Dual perfusion in vivo brain microdialysis was used to monitor extracellular levels of dopamine in the medial prefrontal cortex and ventral striatum during the acquisition and extinction of a classical aversive conditioning paradigm in rats. The main finding was a dissociation in the pattern of release in the two brain areas. The first stimulus-footshock pairing elicited large increases in cortical dopamine over baseline levels that were much greater than the increases elicited by different stimuli of equivalent salience that were unpaired with footshock. In contrast, dopamine levels in ventral striatum were unchanged under these conditions. Over the next two pairings, there was a decline in the cortical response and an increase in the response in ventral striatum. The first presentation of the aversive conditioned stimulus in a separate context elicited the largest response in ventral striatum. Post-conditioning, the cortical response to the conditioned stimulus was smaller than that elicited by the initial stimulus-footshock pairing and was equivalent in magnitude to that elicited by stimuli unpaired with footshock. Over the final two conditioned stimuli presentations, in the absence of the footshock reinforcer (extinction), responses declined in both brain areas. Simultaneous monitoring of behaviour indicated that the neurochemical events were accompanied by effective aversive learning, as indexed by conditioned freezing responses. The data are discussed in terms of the hypothesis that medial prefrontal cortex is especially engaged during novel circumstances which may, potentially, require new learning, whilst ventral striatal dopamine more closely follows the expression of conditioned responding during learning and extinction.     

Interaction with pups enhances dopamine release in the ventral striatum of maternal rats: a microdialysis study

A growing body of evidence suggests that an interference with dopamine (DA) transmission disrupts maternal behavior in the rat. The present brain microdialysis study was therefore conducted to investigate whether infants can modulate ventral striatal DA release in mother rats. There was a significant rise in the extracellular concentrations DA, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in the ventral striatum when mothers were reunited with their litters following separation overnight. Nursing was the predominant behavior during this phase of the experiment. More active behaviors were elicited by soiling pups with flowerpot earth, and this was accompanied by further increases in DA, DOPAC, HVA, and 5-HIAA. It is suggested that pup-induced stimulation of ventral striatal DA release facilitates parental responses such as pup retrieval.     

Estrogen differentially modulates nicotine-evoked dopamine release from the striatum of male and female rats

BACKGROUND: Transluminal balloon angioplasty offers advantages to patch angioplasty. We evaluated the primary patency of thrombosed hemodialysis grafts that had undergone balloon angioplasty versus patch angioplasty as a salvage method. METHODS: We reviewed our experience with 22 consecutive intraoperative balloon angioplasties that were done in a 6-months period. The balloons used were noncompliant high pressure balloons. The balloon results were compared with those of 22 patients who had undergone patch angioplasties by the same surgeons. Age, gender, average time between graft insertion and revision, and number of prior revisions were analyzed. The two groups (patch and balloon) had similar ages (57 versus 58 years, respectively), gender distribution (12 women, 11 men versus 11 women and 11 men), average time of revisions before that particular procedure (15 versus 12 months), and average times of revisions before that procedure. RESULTS: Primary patencies of the patch and balloon group were respectively 86% versus 77% at 1 month, 45% versus 40% at 3 months, and 17% versus 28% at 6 months. There was no statistically significant difference between the two groups. Complications were comparable in both groups. CONCLUSION: Balloon angioplasty offers advantages to patch angioplasty, and we have shown similar patency rates. We recommend balloon angioplasty as a comparable method to salvage dialysis access grafts.     

Deficient passive and one-way active avoidance acquisition following medial forebrain bundle lesions in rats.

In 3 experiments with 93 Long-Evans male hooded rats, cathodal electrolytic lesions of the medial forebrain bundle (MFB) at posterior hypothalamic levels produced a mild, transient hypodipsia and lowered jump thresholds to footshock. Lesions produced marked deficits in passive avoidance performance in a paradigm that paired discrete, linearly incrementing footshock intensities with contact of a water spout following 48 hrs of water deprivation. Injections of levo-dextro-5-hydroxytryptophan (75 mg g, ip), the immediate metabolic precursor of serotonin, had no effect on the passive avoidance performance of either experimental or operated control Ss. Lesions of the MFB also resulted in deficient acquisition in a 1-trial step-through passive avoidance paradigm not using motivation to drink and caused a severe acquisition deficit in a 1-way active avoidance task. Lesions of the septal nuclei produced lowered jump thresholds but did not affect acquisition in the 1st passive avoidance task. Results are interpreted as indicating a lesion-induced deficiency in fear learning, independent of the serotonergic functions of the MFB. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of dopamine and AMPA receptor antagonists on the expression of conditioned avoidance responding in rats.

AMPA receptor antagonists disrupt avoidance responding, but their day-to-day effect on this behavior has not been elucidated. This study compared the multisession effect of the AMPA/kainate receptor antagonist CNQX with that of the typical antipsychotic haloperidol on the expression of avoidance responding. Rats (N = 199) were trained to move to safety on presentation of a tone in one-way active conditioned avoidance and were tested across 5 sessions. Intracerebroventricular (icv) injection of CNQX (20-min injection-test interval) produced a dose-dependent, immediate block of avoidance responding, compared with the extinction-like decline of avoidance responding produced by haloperidol (intraperitoneal [ip], 60-min injection-test interval; icv, 60 but not 20-min injection-test interval). Previous exposure to CNQX significantly reduced its efficacy, illustrating that its effects may not be specific to the conditioned safety-related stimuli that control responding in conditioned avoidance, as proposed for antidopaminergic compounds. The new multisession profile of disrupted avoidance responding illustrated by CNQX suggests different roles for glutamatergic and dopaminergic neurotransmission in conditioned avoidance responding. Results are consistent with a role for AMPA receptors in maintaining the expression of learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The electrical characteristics of the command and motor neurons during the acquisition of a conditioned defensive reflex and the development of long-term sensitization in snails

The mechanisms of conditioning of the defensive pneumostome closure reflex and long-term sensitization were studied at the level of electrical characteristics of the command and motor neurons. A significant decrease in membrane and threshold potentials in the command neurons was observed after the acquisition of the defensive reflex and long-term sensitization. These potentials decreased to a greater extent in the snails subjected to conditioning after the sensitization. Changes in the critical depolarization level for the action potential generation and its amplitude were insignificant. Thus, the observed phenomena testify to an increase in membrane excitability of the command neurons. Similar changes were not found in the motor neurons.     

Effects of Pavlovian conditioned stimulus-unconditioned stimulus pairings during avoidance response-prevention trials in rats.

Response prevention (blocking) has been shown to hasten extinction of an instrumental avoidance response. One interpretation suggests that the facilitation effect is mediated by Pavlovian fear reduction during conditioned stimulus exposure on blocked trials. To test the fear-reduction hypothesis 30 male Holtzman albino rats received either a typical blocking treatment, blocking with shock, or extinction alone. Results indicate that blocking with the UCS was as effective as regular blocking in facilitating extinction of avoidance. An ancillary part of the experiment to assess the effectiveness of response prevention in 30 immature Ss showed that blocking did not facilitate extinction with the weanlings. Findings suggest that facilitated extinction is not solely attributable to Pavlovian fear reduction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The pre- and postsynaptic mechanisms of the involvement of the serotonin of the amygdaloid body in the reproduction of the conditioned passive avoidance reaction in rats

A previous study reported that intercellular adhesion molecule-1 (ICAM-1) expression by human vascular endothelial cells (HUVEC) is augmented by intracellular signal transmission mainly through the protein kinase C (PKC) system stimulated by TXA2 receptors. In the present study, we show that a TXA2 receptor agonist, U46619, augments the expression of not only ICAM-1, but also vascular cell adhesion molecule-1 (VCAM-1) or endothelial leucocyte adhesion molecule-1 (ELAM-1) in HUVEC both at protein and mRNA levels. Pretreatment with SQ29,548 (a TXA2 receptor antagonist) or PKC inhibitors greatly diminished the extent of U46619-induced mRNA accumulation and surface expression of the adhesion molecules. An inhibitor of nuclear factor kappaB (NF-kappaB) activation, PDTC, diminishes U46619-induced VCAM-1 mRNA accumulation. NAC, which inhibits NF-kappaB and activation protein 1 (AP-1) binding activity, inhibits the expression of ICAM-1 or ELAM-1 at protein and mRNA levels. These findings suggest that ICAM-1 or ELAM-1 expression of HUVEC stimulated via TXA2 receptors is augmented by induction of NF-kappaB and AP-1 binding activity through the PKC system, and that VCAM-1 expression is augmented by induction of NF-kappaB binding activity.     

The effects of thiamin and its phosphate esters on dopamine release in the rat striatum

The effect of thiamin and its phosphate esters on dopamine (DA) release was examined in the rat striatum using an in vivo microdialysis. Intrastriatal administration of thiamin triphosphate (TTP) or thiamin diphosphate (TDP) induced DA release, but thiamin monophosphate (TMP) or thiamin did not show any change. In the absence of Ca2+ in the perfusate, TTP did not increase the DA release. omega-Conotoxin did not decrease the TTP-dependent DA release. These findings suggest that, in contrast to TMP and thiamin, TTP and TDP may play a specific role in DA release from nerve terminals.     

Reversible inactivation of the median raphe nucleus enhances consolidation and retrieval but not acquisition of passive avoidance learning in rats

Involvement of median raphe nucleus (MRN) in acquisition, consolidation and retrieval of passive avoidance (PA) was investigated with functional suppression of this area by lidocaine. Rats carrying a chronically implanted cannula aimed at the MRN were trained on a step-through passive avoidance task and received intra-MRN injection of lidocaine or saline 5 min before training or 5, 90 and 360 min after acquisition trial or 5 min before the retrieval test. Lidocaine MRN inactivation had no effect on PA learning. Lidocaine injected 5 and 90 min after the acquisition trial significantly enhanced avoidance of the dark compartment in comparison with the control group injected with saline. But PA retention was not affected by lidocaine injected 360 min after acquisition or 5 min before training. Retention latency significantly increased, when lidocaine injected 5 min before retrieval test. Step-through latency of naive rats was not affected by MRN blockade. Furthermore, reversible inactivation of MRN did not have a significant effect on locomotor activity. Our results indicate that the MRN contributes to PA consolidation at least until 90 min after acquisition and involves in PA retrieval. It is concluded that functional ablation of the MRN may disrupt the inhibitory actions of MRN projections to sub-cortical circuits participating in PA memorization and retrieval.     

Electrical stimulation of the medial prefrontal cortex increases dopamine release in the striatum

Exogenous and endogenous glutamate has been shown to evoke dopamine (DA) release in the striatum using both in vitro and in vivo techniques. We hypothesized that stimulation of the prefrontal cortex (PFC) would phasically enhance striatal DA release via the glutamatergic corticostriatal pathway. To test this hypothesis, in vivo brain microdialysis was employed to measure extracellular concentrations of DA in the striatum during electrical stimulation of the PFC. Five rats were implanted with bilateral electrodes located in the medial PFC and dialysis probes in the dorsal striatum. Two days later the PFC of these awake, freely moving rats was stimulated first at 50 microA and then at 100 microA for 20 minutes at 2-hour intervals. Both currents significantly increased DA release. Extracellular DA rose rapidly during stimulation, peaked immediately afterward, and then slowly returned to baseline values. Dopamine reached 118% of baseline values with 50 microA stimulation and 138% with 100 microA stimulation. Histologic analysis using the fluorescent retrograde dye Fluoro Gold confirmed that cells projecting to the vicinity of the striatal dialysis probe originated in the vicinity of the PFC electrodes. These results provide direct evidence for phasic, excitatory modulation of striatal DA release by the PFC.     

Acquisition of conditioned avoidance responses by hypophysectomized rats.

Maintained hypophysectomized and sham-operated male Wistar rats on a complete high-carbohydrate dietary supplement in addition to ordinary diet to insure a state of good health. Groups so maintained were compared with respect to their ability to acquire the conditioned 2-way avoidance response 2, 3, and 5 wk. after operation. Sham-operated and hypophysectomized Ss both acquired the response with no significant differences. Almost all groups, however, included Ss which did not acquire the response. Hypophysectomized groups contained fewer of these Ss. Examination of a sample from a normal unoperated Wistar population without dietary supplement showed a proportion of Ss which did not acquire the response similar to that found with the sham-operated Ss. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The parabrachial nucleus is essential for acquisition of a conditioned odor aversion in rats.

Rats with bilateral ibotenic acid lesions of the gustatory zone of the parabrachial nuclei (PBN) failed to acquire a conditioned taste aversion (CTA) in Exp 1. They also failed to acquire a conditioned odor aversion (COA) when the olfactory cue was presented on an odor disk in Exp 2 or when it was presented in water in Exp 3. The failure to acquire the COA was not due to an inability to detect or use olfactory stimuli because the lesioned rats displayed neophobia to a novel odor in Exp 3 and used an olfactory cue to predict the availability of an aversive capsaicin solution in Exp 4. Together, the results demonstrate that, as with CTA learning, PBN cell bodies are essential for the establishment of a specific association between an olfactory conditioned stimulus and a lithium chloride unconditioned stimulus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)