Cocaine self-administration in mice is inversely related to phosphorylation at Thr34 (protein kinase A site) and Ser130 (kinase CK1 site) of DARPP-32

The reinforcing effect of cocaine is associated with increases in dopamine in the striatum. The phosphoprotein DARPP-32 (dopamine- and cAMP-regulated phosphoprotein) has been shown to mediate the intracellular events after activation of dopamine receptors. DARPP-32 is phosphorylated at multiple sites by different protein kinases, but little is known about the functional role of these different sites. Cocaine self-administration and striatal levels of dopamine after acute "binge" cocaine administration were measured in separate lines of mice with alanine mutations introduced into DARPP-32 at either Thr34 (protein kinase A site, Thr34A), Thr75, (cyclin-dependent kinase 5 site, Thr75A), Ser97 (kinase CK2 site, Ser97A), or Ser130 (kinase CK1 site, Ser130A). Acquisition of stable cocaine self-administration required significantly more time in Thr34A-/- mice. Both Thr34A- and Ser130A-DARPP-32 mutant mice self-administered more cocaine than their respective wild-type controls. Also, cocaine-induced increases of dopamine in dorsal striatum were attenuated in the Thr34A- and Ser130A-DARPP-32 phosphomutant mice compared with wild-type mice. Notably, levels of P-Thr34- and P-Ser130-DARPP-32 were reduced after self-administration of cocaine in wild-type mice. Thus, phosphorylation states of Thr34- and Ser130-DARPP-32 play important roles in modulating the reinforcing effects of cocaine.

Amygdalar vasopressin mRNA increases in acute cocaine withdrawal: evidence for opioid receptor modulation

In humans, stress is recognized as a major factor contributing to relapse to drug abuse in abstinent individuals; drugs of abuse themselves or withdrawal from such drugs act as stressors. In the animals, evidence suggests that centrally released arginine vasopressin in both amygdala and hypothalamus plays an important role in stress-related anxiogenic behaviors. The stress responsive hypothalamic-pituitary-adrenal axis is under tonic inhibition via endogenous opioids, and cocaine withdrawal stimulates hypothalamic-pituitary-adrenal activity. The present studies were undertaken to determine whether: (1) 14-day (chronic) "binge" pattern cocaine administration (45 mg/kg/day) or its withdrawal for 3 h (acute), 1 day (subacute) or 10 days (chronic) alters arginine vasopressin mRNA levels in amygdala or hypothalamus; (2) the opioid receptor antagonist naloxone (1mg/kg) alters arginine vasopressin mRNA or hypothalamic-pituitary-adrenal hormonal responses in acute cocaine withdrawal; and (3) there are associated changes of mu opioid receptor or proopiomelanocortin mRNA levels. In amygdala, arginine vasopressin mRNA levels were unchanged after chronic "binge" cocaine, but were increased during acute cocaine withdrawal. Naloxone completely blocked this increase. Neither chronic cocaine nor its acute withdrawal altered amygdalar mu opioid receptor mRNA levels. The increase in amygdalar arginine vasopressin mRNA levels was still observed after subacute withdrawal, but not after chronic withdrawal. Although hypothalamic-pituitary-adrenal tolerance developed with chronic "binge" cocaine, there were modestly elevated plasma adrenocorticotropin hormone levels during acute withdrawal. While naloxone produced modest adrenocorticotropin hormone elevations in cocaine-naïve rats, naloxone failed to elicit an adrenocorticotropin hormone response in cocaine-withdrawn rats. In hypothalamus, neither chronic cocaine nor acute withdrawal altered arginine vasopressin, proopiomelanocortin or mu opioid receptor mRNA levels. These results show that: (1) opioid receptors mediate increased amygdalar arginine vasopressin gene expression during acute cocaine withdrawal, and (2) cocaine withdrawal renders the hypothalamic-pituitary-adrenal axis insensitive to naloxone. Our findings suggest a potential role for amygdalar arginine vasopressin in the aversive consequences of early cocaine withdrawal.

A cerebral palsy assessment tool using anatomically based geometries and free-form deformation

A geometrical analysis tool for investigating muscle length change in cerebral palsy (CP) patients is presented. A subset of anatomically based geometries from the International Union of Physiological Sciences (IUPS) Physiome Project is used, which is derived from the visible human (VH) data set with muscle attachment information, and customised using volume-preserving free-form deformation (FFD), the 'host-mesh' technique. The model's intended use is to provide pre- and post-surgery assessment for muscle lengthening, a surgery performed to help slacken tight muscles and improve gait. The model is illustrated using healthy patient data from motion capture as a validation followed by three CP case studies to highlight its use. The methodology is presented in three stages, (1) a FFD of the complete lower limb, (2) a focused geometric study on the semimembranosus (SM) and gastrocnemius (GT) muscles, and (3) an improved hybrid mechanics-FFD approach as an improvement for future analysis, with differentiation between muscle and tendon lengthening, and contact detection between sliding muscles. Finally, the issues, limitations, in particular with the marker system, and model improvements are discussed.

Isochromosome of a deleted 20q: a rare but recurrent chromosome abnormality in myelodysplastic syndromes

Interstitial deletion of the long arm of chromosome 20, as the sole abnormality, is commonly observed in myeloid malignancies, including myeloproliferative disorder, myelodysplastic syndrome, and acute myeloid leukemia. The breakpoints of the deletion are typically located in the region 20q11.2 approximately q13.3, although smaller deletions within this region have also been reported. We present here 4 patients with myelodysplastic syndrome with an isochromosome of the deleted long arm of chromosome 20: ider(20)(q10)del(20)(q11q13). Fluorescence in situ hybridization studies were performed on the bone marrow samples from these patients to prove the identity of this unusual chromosome abnormality.

Rituximab is effective in the management of refractory autoimmune cytopenias occurring after allogeneic stem cell transplantation

Autoimmune haemolytic anaemia (AIHA), immune thrombocytopenia (ITP) and autoimmune neutropenia (AIN) are well-recognised complications of allogeneic stem cell transplantation (SCT), but have previously only been reported in the context of myeloablative conditioning regimens. Management of AIHA, ITP or AIN occurring after allogeneic SCT is unsatisfactory since they frequently prove refractory to conventional therapies including splenectomy. As a consequence, autoimmune cytopenias occurring after allogeneic SCT are associated with substantial morbidity and mortality. We report four patients who developed AIHA or ITP after allogeneic transplantation -- three of which occurred after a reduced-intensity conditioning (RIC) regimen. All patients demonstrated a complete response to Rituximab, having failed to respond to conventional treatment including high-dose prednisolone and intravenous immunoglobulin (IVIg). We conclude that Rituximab can be a valuable agent in the management of autoimmune cytopenias occurring after allogeneic SCT and that autoimmune cytopenias may be a hitherto unrecognised complication of RIC regimens.

Targeted Degradation of Proteins by Small Molecules: A Novel Tool for Functional Proteomics†

A novel strategy that targets protein for degradation has recently been developed by exploiting a protein-targeting chimeric molecule ('Protac'). Typically, the chimeric Protac is composed of a small-molecule ligand ('bait') on one end and a synthetic octapeptide on the other. This octapeptide is recognized by E3 ubiquitin ligase pVHL (von Hippel Lindau tumor suppressor protein), thereby recruiting a small molecule-bound protein ('prey') to pVHL for ubiquitination and degradation. Since selective degradation of a cellular protein generates a "loss of function" mutation, this protein knock-out strategy may be useful to study the function of a given protein or to evaluate whether a cellular protein is a potential target for drug intervention, in a manner reminiscent of gene knock-out or siRNA approaches. Herein, we show that a synthetic pentapeptide is sufficient to interact with pVHL E3 ligase, and that the pentapeptide-based Protac efficiently induces ubiquitination and degradation of target protein. Our results also demonstrate that the pentapeptide-based Protac can enter cells efficiently to exerts its biological activity effectively. These results suggest that the synthetic pentapeptide can be used either directly in the preparation of cell-permeable Protacs or as a template to develop peptidomimetic or non-peptide Protacs.

Neuroendocrine alterations in a high-dose, extended-access rat self-administration model of escalating cocaine use

One approach for studying cocaine addiction has been to permit escalating patterns of self-administration (SA) by rats by prolonging daily drug availability. Rats provided long access (LgA) to high cocaine doses, but not rats provided shorter cocaine access (ShA), progressively escalate their cocaine intake and display characteristics of human addiction. The purpose of the present study was to investigate the effects of 14 days of ShA or LgA, high-dose cocaine SA on plasma corticosterone (CORT), prolactin (PRL), and related mRNAs. Acutely, cocaine SA increased plasma CORT and reduced plasma PRL levels. SA training produced circadian increases in CORT that appeared to occur in anticipation of cocaine availability. With repeated LgA, high-dose SA, the daily CORT area under the curve (AUC) progressively decreased, apparently due to tolerance to cocaine's effects on CORT and a reduction in basal CORT levels. In contrast, the daily CORT AUC in ShA rats increased across testing despite constant rates of SA. When measured 12 days after SA testing, pro-opioimelanocortin and glucocorticoid receptor mRNA levels in the anterior pituitary were lower in LgA rats than in ShA rats. The effects of SA on PRL remained constant across SA testing in LgA rats, but increased in duration in ShA rats. Anterior pituitary dopamine D2 receptor mRNA levels were lower in LgA rats than in ShA rats. These findings indicate that the transition to escalating patterns of SA may be associated with altered levels of hormones and gene expression within neuroendocrine systems. Such changes may underlie the onset of human addictive disease.

NECABs: a family of neuronal Ca(2+)-binding proteins with an unusual domain structure and a restricted expression pattern

Ca(2+)-signalling plays a major role in regulating all aspects of neuronal function. Different types of neurons exhibit characteristic differences in the responses to Ca(2+)-signals. Correlating with differences in Ca(2+)-response are expression patterns of Ca(2+)-binding proteins that often serve as markers for various types of neurons. For example, in the cerebral cortex the EF-hand Ca(2+)-binding proteins parvalbumin and calbindin are primarily expressed in inhibitory interneurons where they influence Ca(2+)-dependent responses. We have now identified a new family of proteins called NECABs (neuronal Ca(2+)-binding proteins). NECABs contain an N-terminal EF-hand domain that binds Ca(2+), but different from many other neuronal EF-hand Ca(2+)-binding proteins, only a single EF-hand domain is present. At the C-terminus, NECABs include a DUF176 motif, a bacterial domain of unknown function that was previously not observed in eukaryotes. In rat at least three closely related NECAB genes are expressed either primarily in brain (NECABs 1 and 2) or in brain and muscle (NECAB 3). Immunocytochemistry revealed that NECAB 1 is restricted to subsets of neurons. In cerebral cortex, NECAB 1 is highly and uniformly expressed only in layer 4 pyramidal neurons, whereas in hippocampus only inhibitory interneurons and CA2 pyramidal cells contain NECAB 1. In these neurons, NECAB 1 fills the entire cytoplasm similar to other EF-hand Ca(2+)-binding proteins, and is not concentrated in any particular subcellular compartment. We suggest that NECABs represent a novel family of regulatory Ca(2+)-binding proteins with an unusual domain structure and a limited expression in a subclass of neurons.

Effect of acute binge cocaine on levels of extracellular dopamine in the caudate putamen and nucleus accumbens in male C57BL/6J and 129/J mice

Levels of dopamine, both basal and after binge-pattern cocaine administration, were measured in the caudate putamen and nucleus accumbens of C57BL/6J and 129/J mice by in vivo microdialysis. Six-week old males were surgically implanted with a CMA guide cannula into the caudate putamen or nucleus accumbens. After 4 days recovery, dialysis probes were lowered into the caudate putamen or the nucleus accumbens and mice were placed in individual microdialysis chambers. The next morning experiments were carried out on freely moving animals. Experimental animals received 1-day binge cocaine administration (15 mg/kgx3, i.p. at hourly intervals) while control animals received saline in the same pattern. Dialysates were collected every 20 min and dopamine content was determined by HPLC with electrochemical detection. Basal levels of dopamine in the dialysate of the caudate putamen were 4.2+/-0.2 nM in C57BL/6J mice and 5.0+/-0.3 nM in 129/J mice. In the nucleus accumbens, basal levels of dopamine were 0.65+/-0.04 nM in the C57BL/6J mice and 0.75+/-0.03 nM in 129/J mice, with no significant differences between strains in either region. Binge cocaine administration significantly increased mean dopamine levels in the caudate putamen in the C57BL/6J mice (with a 3-h mean of 6.80 nM) and in the 129J mice (9.94 nM). In this region, 129/J mice had significantly higher levels of cocaine-induced dopamine than did C57BL/6J mice. In the nucleus accumbens, administration of cocaine also significantly increased dopamine levels in both strains (1.32 nM in C57BL/6J and 1.43 nM in 129/J), but with no difference between strains.

Tear exchange under hydrogel contact lenses: methodological considerations

PURPOSE

To characterize hydrogel lens tear exchange and to apply an optimized method to compare tear exchange of a marketed hydrogel lens to that measured with a prototype silicone hydrogel lens.

METHODS

Fluorophotometry and a nonpenetrating tracer (70-kDa FITC-dextran) were used with a single extended-wear soft contact lens (EWSCL) material on 11 subjects to characterize tear-exchange kinetics. Twenty to 30 measurements were obtained over a 30-minute period to allow accurate modeling and estimation of the several tear-exchange parameters. Calculated values included tear-replenishment rate (TRR), elimination rate (ER), and the time for 95% of the signal to be eliminated (T(95)). Major experiments were (1) comparison of ER under controlled and physiological conditions, (2) comparison of right and left eyes, (3) repeatability of ER and T(95) on five occasions, and (4) comparison of a marketed lens (oxygen permeability [Dk] 28 x 10(-9) [cm/sec][ml O(2)/ml mm Hg]) to a prototype silicone hydrogel lens (Dk 140 x 10(-9) [cm/sec][ml O(2)/ml mm Hg]).

RESULTS

Tracer elimination behind a hydrogel contact lens (CL), up to 30 minutes after insertion, was optimally described by double-exponential kinetics. Physiological ER (5-30 minutes after CL insertion) was optimally described by single-exponential kinetics. Overall, physiological ER was 8.8% +/- 3.8% per minute, and T(95) was 31.0 +/- 16.1 minutes (n = 76 and 72 determinations, respectively). Differences between right and left eyes in ER and T(95) were not significant at the 0.05 level. No difference in ER or T(95) was found between habitual and controlled blinking. Mean TRR was 0.67% +/- 0.26% per blink (n = 11 determinations). No differences were shown between ER or T(95) measurements over time. A prototype highly oxygen-permeable silicone hydrogel lens showed higher ER than did a marketed hydrogel lens (P < 0.01).

CONCLUSIONS

Estimates of postlens tear exchange using a slit lamp fluorophotometer are similar to previously reported rates using similar fluorophotometric techniques. Fluorescent decay behind a hydrogel lens is most precisely described using a double-exponential curve equation and tear exchange may be described using ER, TRR and T(95), although the T(95) may be the least reliable of these measures. The technique appears capable of discriminating between lens types.

Hypothalamic CRH mRNA levels are differentially modulated by repeated 'binge' cocaine with or without D(1) dopamine receptor blockade

We previously found that there was a rapid stimulatory effect of acute (1 day) 'binge' cocaine on CRH mRNA levels in the rat hypothalamus. In contrast, after 3 days of 'binge' cocaine, there was a modest decrease (12%) in hypothalamic CRH mRNA levels, which after 14 days of 'binge' cocaine was greater (32%) and significantly lower than control values. Also, our previous studies found an elevation of CRH mRNA in the frontal cortex after 3 days of 'binge' cocaine. The present study was designed to investigate the possible role of dopamine receptors in modulating these effects. Administration of 3 days of 'binge' cocaine (3 x 15 mg/kg, i.p.) was preceded by daily injections of either D(1) (SCH23390, 2 mg/kg) or D(2) (sulpiride, 50 mg/kg) dopamine receptor antagonist. Neither SCH23390 nor sulpiride had an effect on basal CRH mRNA levels in the hypothalamus, frontal cortex or amygdala. Small decreases (10-13%) in hypothalamic CRH mRNA levels were found again to be induced by 3 days of repeated 'binge' cocaine. However, this modest decrease was not found in the rats that received D(1) antagonist SCH23390 pretreatment. Pretreatment with D(2) antagonist sulpiride had no effect on this decrease. These findings suggest that the inhibitory effect of repeated 'binge' cocaine on the hypothalamic CRH mRNA expression is absent when there is D(1), but not D(2), dopamine receptor blockade. In the frontal cortex, pretreatment with either SCH23390 or sulpiride did not alter the increases in the CRH mRNA levels induced by repeated 'binge' cocaine. The results suggest that the cocaine-induced modulation of hypothalamic CRH mRNA expression is secondary to changes in the activity of specific components of dopaminergic systems.

Decreases in anti-double-stranded DNA levels are associated with concurrent flares in patients with systemic lupus erythematosus

OBJECTIVE

To determine the degree to which changes in anti-double-stranded DNA (anti-dsDNA), as determined by Crithidia and enzyme-linked immunosorbent assays (ELISAs), precede or coincide with changes in systemic lupus erythematosus (SLE) activity, as measured by 5 clinical indices, the physician's global assessment (PGA), modified SLE Disease Activity Index (M-SLEDAI), modified Lupus Activity Index (M-LAI), Systemic Lupus Activity Measure (SLAM), and the modified British Isles Lupus Assessment Group (M-BILAG).

METHODS

Disease activity and anti-dsDNA were measured monthly in 53 SLE patients who were followed up for 1 year. Lupus flare was defined as an increase in PGA of > or = 1.0, M-SLEDAI > or = 3, M-LAI > or = 0.1, SLAM > or = 3, and M-BILAG > or = 4 within a 1-month period. Flare rates were calculated for groups, which were defined by "previous" (1 month prior to the flare) or "concurrent" (at the time of the flare) changes in anti-dsDNA. Logistic regression models were used to determine the significance of the association between recent changes in anti-dsDNA and flare, controlling for the prednisone dosage.

RESULTS

Flares occurred at 12% of visits, based on the PGA measure of disease activity. Using the other indices, flare rates were 19% (M-SLEDAI), 25% (M-LAI), 13% (SLAM), and 12% (M-BILAG). A concurrent decrease in anti-dsDNA (ELISA) was associated with significantly higher flare rates based on PGA (18 of 84, 21%; P = 0.0014), M-SLEDAI (27 of 89, 30%; P = 0.0019), M-LAI (37 of 89, 42%; P = 0.0001), and M-BILAG (19 of 89, 21%; P = 0.0264) scores. Flare rates were also significantly higher after a previous increase in anti-dsDNA (ELISA) based on M-SLEDAI (26 of 93, 30%; P = 0.0022) and M-LAI (34 of 93, 37%; P = 0.0117) scores. Flare rates tended to be lowest when there was a concurrent increase in anti-dsDNA (ELISA). Analysis of specific organ systems showed that a concurrent decrease in anti-dsDNA (ELISA) was significantly associated with increases in renal disease activity. Similar results were obtained using the Crithidia assay.

CONCLUSION

A previous increase in anti-dsDNA levels occurred before SLE flares, as measured by the M-SLEDAI and M-LAI only. However, during lupus flares, including the subset of renal flares, anti-dsDNA levels frequently decreased. We hypothesize that this decrease in anti-dsDNA represents deposition in tissue at the time of flare.

A decrease in complement is associated with increased renal and hematologic activity in patients with systemic lupus erythematosus

OBJECTIVE

To determine the degree to which changes in C3 and C4 precede or coincide with changes in systemic lupus erythematosus (SLE) activity, as measured by 5 global activity indices, the physician's global assessment (PGA), modified SLE Disease Activity Index (M-SLEDAI), modified Lupus Activity Index (M-LAI), Systemic Lupus Activity Measure (SLAM), and the modified British Isles Lupus Assessment Group (M-BILAG), and to evaluate the association between changes in C3 and C4 levels and SLE activity in individual organ systems.

METHODS

Fifty-three lupus patients were observed monthly for 1 year in a longitudinal study. Lupus disease activity and complement levels were measured at each visit. Lupus flare was defined as a 1.0 (or greater) increase in the PGA, a 3-point increase in the M-SLEDAI, a 0.1 increase in the M-LAI, a 3-point increase in the SLAM, or a 4-point increase in the M-BILAG within a 1-month period. Flare rates were calculated for subgroups defined by previous (1 month before) or concurrent changes in complement levels. Logistic regression models were used to determine the significance of the association between recent changes in complement levels and flare, controlling for prednisone dosage. Similar models were used to assess the association between changes in C3 or C4 levels and increased SLE activity in specific organ systems.

RESULTS

Lupus flares occurred at 12% of visits based on the PGA, 19% based on the M-SLEDAI, 25% based on the M-LAI, 13% based on the SLAM, and 12% based on the M-BILAG. Recent changes in C3 and C4 levels were not associated with flares based on 3 of the 5 activity indices. Flares defined by the M-LAI were more frequent when there was a concurrent decrease in C3 (odds ratio [OR] 1.9, 95% confidence interval [95% CI] 1.1-3.1) or C4 (OR 2.1, 95% CI 1.3-3.6). Higher flare rates, as defined by the SLAM, were associated with previous increases in C3 (OR 1.6, 95% CI 1.0-2.6) and C4 (OR 2.2, 95% CI 1.2-3.9). When individual organ systems were analyzed, decreases in C3 and C4 were associated with a concurrent increase in renal disease activity (OR 2.2, 95% CI 1.4-3.5 and OR 1.9, 95% CI 1.1-3.4, respectively). Decreases in C3 were also associated with concurrent decreases in the hematocrit (OR 4.6, 95% CI 1.7-12.3), platelet (OR 2.5, 95% CI 1.5-4.1), and white blood cell (OR 2.2, 95% CI 1.3-3.6) counts. Previous increases in C3 levels were associated with a decrease in platelets (OR 1.7, 95% CI 1.1-2.7). A decrease in C4 was associated with a concurrent decrease in the hematocrit level (OR 3.2, 95% CI 1.3-7.5) and platelet count (OR 1.6, 95% CI 1.0-2.5).

CONCLUSION

Decreases in complement levels were not consistently associated with SLE flares, as defined by global measures of disease activity. However, decreasing complement was associated with a concurrent increase in renal and hematologic SLE activity.

Ablation of pituitary pro-opiomelanocortin (POMC) cells produces alterations in hypothalamic POMC mRNA levels and midbrain mu opioid receptor binding in a conditional transgenic mouse model

The hypothalamic-pituitary-adrenal (HPA) axis is regulated by stress-related excitatory inputs, and various inhibitory and negative-feedback controls by glucocorticoids and opioids, including pro-opiomelanocortin (POMC)-derived peptides. The role of POMC-derived peptides of pituitary origin in the modulation of brain POMC mRNA expression and opioid receptor binding was investigated using a line of transgenic mice that express a fusion gene composed of the pituitary expression-specific promoter region of the POMC gene driving the herpes simplex viral-1 thymidine kinase (TK). Male adult mice were treated with the antiherpes agent ganciclovir that selectively ablates cells expressing TK. Following treatment, POMC mRNA levels, measured by quantitative solution hybridization/RNase protection assays, were decreased by 48% in the pituitary of the TK+/+ mice, reflecting an expected loss of the pituitary corticotrope POMC cells. This treatment also significantly lowered pituitary beta-endorphin immunoreactivity content and plasma concentrations of corticosterone. In contrast, POMC mRNA levels were increased by 79% in the hypothalamus of the TK+/+ mice with pituitary POMC cell ablation. Binding of [(3)H]DAMGO to mu opioid receptors, as measured by quantitative autoradiography, was significantly reduced in several brain regions including the central grey, median raphe and superficial grey layer of the superior colliculus. These regions are innervated by hypothalamic POMC neurones. No significant differences in binding to either kappa or delta opioid receptors were found in the brain regions studied. These results suggest that POMC-derived peptides of pituitary origin may exert a tonic negative-feedback effect on hypothalamic POMC neurones. In turn, the downregulation of central mu opioid receptors in this model may be mediated through a mechanism related to hypothalamic POMC overexpression.

Mammary epithelial cell-cycle progression via the alpha(2)beta(1) integrin: unique and synergistic roles of the alpha(2) cytoplasmic domain

The alpha(2)beta(1) integrin supports cell-cycle progression of mammary epithelial cells adherent to type I collagen matrices. Integrin collagen receptors containing the alpha(2) cytoplasmic domain stimulated expression of cyclin E and cyclin-dependent kinase (cdk)2, resulting in cyclin E/cdk2 activation in the absence of growth factors other than insulin. Integrin collagen receptors in which the alpha(2) cytoplasmic domain was replaced by the alpha(1) cytoplasmic domain or an alpha(2) subunit cytoplasmic domain truncated after the GFFKR sequence failed to stimulate cyclin E/cdk2 activation or entry into S phase in the absence of growth factors. Although overexpression of cyclins D or E or cdk2 in cells expressing the integrin collagen receptor with the alpha(1)-integrin cytoplasmic domain did not restore G(1) progression when mammary epithelial cells adhered to type I collagen, co-expression of cyclin E and cdk2 did rescue the ability of the transfectants to enter S phase. Activation of cyclin E/cdk2 complex by mammary epithelial cells required synergy between adhesion mediated by an integrin collagen receptor containing the alpha(2)-integrin subunit cytoplasmic domain and the insulin receptor.

Predictable individual differences in the initiation of cocaine self-administration by rats under extended-access conditions are dose-dependent

RATIONALE

The characterization of self-administration (SA) under extended access conditions is necessary for the development of addiction models.

OBJECTIVE

The purposes of this experiment were to investigate: (1) dose effects on the initiation of cocaine SA under extended access conditions; (2) predictable individual differences in SA under these conditions and their relationships to neuroendocrine function and cocaine dose.

METHODS

After they were tested for their locomotor responses to novelty and to cocaine and trained to lever-press under a food-reinforced schedule, male Sprague-Dawley rats were allowed to SA cocaine (0.25, 0.5, 1.0, or 2.0 mg/kg per infusion, IV) by lever-pressing under a FR1 schedule during five consecutive daily 10-h sessions. Plasma corticosterone (CORT) and prolactin (PRL) were measured throughout the experiment.

RESULTS

Rats tested at higher cocaine doses more readily acquired and showed increased drug intake and more regular patterns of SA. High responders (HR) to novelty self-administered greater amounts of cocaine, acquired more rapidly and displayed more regular SA compared to LR rats, but only at the lowest cocaine dose tested (i.e., 0.25 mg/kg per infusion). HR rats also exhibited a greater high-dose escalation of SA compared to LR rats. Novelty-induced (but not cocaine-induced) locomotor activity, pre-SA plasma CORT, and pre-SA food-reinforced lever-pressing predicted SA, but only at the lowest cocaine dose tested. No differences in plasma CORT or PRL were observed between LR and HR rats.

CONCLUSIONS

The present findings indicate that predictable individual differences in cocaine SA under extended access conditions are relevant only at low doses and are surmountable by increasing the available dose of cocaine.