Time courses of pCREB expression after dopaminergic stimulation by apomorphine in mouse brain

Effects of desipramine treatment on stress-induced up-regulation of norepinephrine transporter expression in rat brains

RATIONALE

Many studies demonstrate down-regulation of the norepinephrine transporter (NET) by desipramine (DMI) in vitro and in stress-naive rats. Little is known regarding regulation of the NET in stressed animals.

OBJECTIVE

The present study was designed to investigate effects of DMI on the expression of NET and protein kinases in the stress rat.

METHODS

Adult Fischer 344 rats were subjected to chronic social defeat (CSD) for 4 weeks. DMI (10 mg/kg, intraperitoneal (i.p.)) was administered concurrently with CSD or 1 or 2 weeks after cessation of CSD. Sucrose consumption, NET expression, and protein kinases were measured.

RESULTS

CSD significantly increased messenger RNA (mRNA) and protein levels of NET in the locus coeruleus, as well as NET protein levels in the hippocampus, frontal cortex, and amygdala. These effects were nearly abolished when DMI was administered concurrently with CSD. CSD-induced up-regulation of NET expression in the locus coeruleus, hippocampus, and amygdala lasted at least 2 weeks after cessation of CSD, an effect that was significantly attenuated by 1 or 2 weeks of DMI treatment starting from cessation of the CSD. Concurrent administration of DMI with CSD did not markedly interfere with CSD-induced decreases in protein levels of protein kinases A and C in these brain regions, but it did reverse the CSD-induced reduction in phosphorylated cAMP response element-binding (pCREB) protein levels in most brain regions.

CONCLUSION

These findings suggest that NET regulation by DMI occurs in both stressed and behaviorally naive rats, and DMI-induced changes in pCREB may be involved.

Apomorphine-induced activation of dopamine receptors modulates FGF-2 expression in astrocytic cultures and promotes survival of dopaminergic neurons

Apomorphine (APO), a potent D1/D2 dopamine receptor agonist, is currently used as an antiparkinsonian drug. We have shown previously that APO stimulates synthesis and release of multiple trophic factors, such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), in both mesencephalic and striatal neurons, thereby effectively preventing dopaminergic neuron loss in vitro. The present study was designed to investigate the effects of APO on fibroblast growth factor-2 (FGF-2) expression and regulation in astrocytes, and furthermore, to identify signaling mechanisms underlying these effects. Here, we show that FGF-2 expression is robustly induced in cultured astrocytes in response to APO. FGF-2 expression was proportional to APO concentration and time-dependent. Conversely, treatment with S-APO, a derivative of R-APO lacking DA receptor agonist activity, did not alter FGF-2 levels. APO treatment resulted in enhanced cytosol FGF-2 immunoreactivity, export of high MW forms of FGF-2 to the cytoplasm from the nucleus and increased extracellular release of FGF-2. Interestingly, both high and low MW forms of FGF-2 were detectable in conditioned medium of APO-treated cultures. This APO-induced effect was correlated with activation of D1 and D2 receptors, as it could be either mimicked by dopamine receptor agonists (SKF38393, quinpirole) or partially blocked by antagonists (SCH23390, SKF83566, haloperidol). Activation of the D1 receptor preferentially increased PKA activity, whereas activation of the D2 receptor only promoted phosphorylation of MAPK. Importantly, APO-modulated FGF-2 expression was independent of Akt/phosphoinositide 3-kinase signaling. These data suggest that APO can enhance biosynthesis and release of FGF-2 through activation of dopamine receptors in striatal astrocytes. Both cAMP/PKA and MEK/MAPK signaling cascades are major steps mediating this process.

Differences in basal levels of CREB and NPY in nucleus accumbens regions between C57BL/6 and DBA/2 mice differing in inborn alcohol drinking behavior

An increasing body of evidence suggests that genetic factors play a role in alcohol drinking behaviors. C57BL/6J (C57) mice innately consume larger amounts of alcohol compared to that consumed by DBA/2J (DBA) mice. Furthermore, alterations in cAMP-responsive element binding (CREB) protein function in the brain have been implicated in alcohol drinking behaviors. The present investigation examined innate expression and phosphorylation of CREB in various brain structures of C57 and DBA mice. It was found that CREB expression and phosphorylation was lower, specifically in the shell structure of the nucleus accumbens, in C57 mice compared to that in DBA mice. CREB expression and phosphorylation were similar in other brain regions such as the nucleus accumbens core and the cortical, amygdaloid, hippocampal, and striatal structures of C57 and DBA mice. The expression of a cAMP-inducible gene, neuropeptide Y (NPY), was also investigated in the nucleus accumbens region of C57 and DBA mice. It was found that in C57 mice, NPY protein levels were lower in the shell but not in the core structure of the nucleus accumbens compared to that in DBA mice. It was also found that C57 mice are not innately anxious, but they consume larger amounts of alcohol than do DBA mice. Because the shell structure of the nucleus accumbens has been implicated in reward mechanisms of alcohol, it is possible that lower CREB function in this brain structure may be in part associated with the excessive alcohol drinking behavior of C57 mice.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation. condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2002 to June 2003 is reviewed, with 568 references cited.