Excessive alcohol use, a major cause of morbidity and mortality, is less well understood than other addictive disorders. Dopamine release in ventral striatum is a common element of drug reward, but alcohol has an unusually complex pharmacology, and humans vary greatly in their alcohol responses. This variation is related to genetic susceptibility for alcoholism, which contributes more than half of alcoholism risk. Here, we report that a functional OPRM1 A118G polymorphism is a major determinant of striatal dopamine responses to alcohol. Social drinkers recruited based on OPRM1 genotype were challenged in separate sessions with alcohol and placebo under pharmacokinetically controlled conditions, and examined for striatal dopamine release using positron emission tomography and [11C]-raclopride displacement. A striatal dopamine response to alcohol was restricted to carriers of the minor 118G allele. To directly establish the causal role of OPRM1 A118G variation, we generated two humanized mouse lines, carrying the respective human sequence variant. Brain microdialysis showed a four-fold greater peak dopamine response to an alcohol challenge in h/mOPRM1-118GG than in h/mOPRM1-118AA mice. OPRM1 A118G variation is a genetic determinant of dopamine responses to alcohol, a mechanism by which it likely modulates alcohol reward.

Paradigm-shifting modalities to more efficiently deliver drugs to cancerous lesions require the following attributes: nanoscale-size, targetability and stability under physiological conditions. Often, these nanoscale drug delivery vehicles are limited due to agglomeration, poor solubility or cytotoxicity. Thus, we have designed a methodology to encapsulate hydrophobic antineoplastic chemotherapeutics within a 20-30 nm diameter, pH-responsive, non-agglomerating, non-toxic calcium phosphate nanoparticle matrix. In the present study, we report on calcium phosphate nanocomposite particles (CPNP) that encapsulate both fluorophores and chemotherapeutics, are colloidally stable in physiological solution for extended time at 37°C and can efficaciously deliver hydrophobic antineoplastic agents, such as ceramide, in several cell model systems.

Calcium current modulation by the muscarinic cholinergic agonist oxotremorine methiodide (oxo-M) was examined in sympathetic neurons from the superior cervical ganglion of the rat. Oxo-M strongly inhibited calcium currents via voltage-dependent (VD) and voltage-independent (VI) pathways. These pathways could be separated with the use of the specific M(1) acetylcholine receptor antagonist M(1)-toxin and with pertussis toxin (PTX) treatment. Expression by nuclear cDNA injection of the regulator of G-protein signaling (RGS2) or a phospholipase Cbeta1 C-terminal construct (PLCbeta-ct) selectively reduced VI oxo-M modulation in PTX-treated and untreated cells. Expression of the Gbetagamma buffers transducin (Galpha(tr)) and a G-protein-coupled-receptor kinase (GRK3) construct (MAS-GRK3) eliminated oxo-M modulation. Activation of the heterologously expressed neurokinin type 1 receptor, a Galpha(q/11)-coupled receptor, resulted in VI calcium current modulation. This modulation was eliminated with coexpression of Galpha(tr) or MAS-GRK3. Cells expressing Gbeta(1)gamma(2) were tonically inhibited via the VD pathway. Application of oxo-M to these cells produced VI modulation and reduced the amount of current inhibited via the VD pathway. Together, these results confirm the requirement for Gbetagamma in VD modulation and implicate Galpha(q)-GTP and Gbetagamma as components in the potentially novel VI pathway.

Abstract-Cyclic nucleotides are known to modify voltage-gated (L-type) Ca 2ϩ channel activity in vascular smooth muscle cells, but the exact mechanism(s) underlying these effects is not well defined. The purpose of the present study was to investigate the modulatory role of the cAMP-and cGMP-dependent protein kinase (PKA and PKG, respectively) pathways in Ca 2ϩ channel function by using both conventional and perforated-patch-clamp techniques in rabbit portal vein myocytes. The membrane-permeable cAMP derivative, 8-bromo cAMP (0.1 to 10 mol/L), significantly increased (14% to 16%) peak Ba 2ϩ currents, whereas higher concentrations (0.05 to 0.1 mmol/L) decreased Ba 2ϩ currents (23% to 31%). In contrast, 8-bromo cGMP inhibited Ba 2ϩ currents at all concentrations tested (0.01 to 1 mmol/L). Basal Ca V oltage-dependent (L-type) Ca 2ϩ channels play a major role in excitation-contraction coupling in vascular smooth muscle cells. L-type Ca 2ϩ channels are known to be modulated by several intracellular second-messenger systems, including both the cAMP/cAMP-dependent protein kinase (PKA) and cGMP/cGMP-dependent protein kinase (PKG) pathways.1 However, for vascular smooth muscle, little information is known regarding the exact mechanism(s) by which these processes take place. Patch-clamp studies in smooth muscle cells have shown that L-type Ca 2ϩ channel activity can be enhanced by either low concentrations of 8-Br cAMP or the catalytic subunit of PKA. 2-4Stimulation of ␤-adrenergic receptors with Iso has also been shown to increase Ca 2ϩ channel currents. 2,3,[5][6][7] On the other hand, 8-Br cGMP or the NO-releasing agents sodium nitroprusside and SNAP have been reported to lead to a decrease of Ca 2ϩ channel activity. 2,8 -10The precise mechanism underlying the effects of both PKA and PKG on L-type Ca 2ϩ channels remains controversial. A previous study from this laboratory showed that a moderate increase in cAMP elicited with 1 mol/L Iso, 1 mol/L FSK, or 0.1 mmol/L 8-Br cAMP increased Ca 2ϩ channel currents. 2On the other hand, higher levels of cAMP elicited with 10 mmol/L Iso, 10 mol/L FSK, 1 mmol/L 8-Br cAMP, or 0.1 mmol/L 8-Br cGMP led to inhibition of Ca 2ϩ channel currents. Experiments that measured the time course of responses to high concentrations of Iso or FSK revealed that Ca 2ϩ channel currents were initially enhanced and subsequently inhibited. It has been suggested that moderate increases in cAMP enhance Ca 2ϩ channel currents through PKA activation, whereas higher levels of cAMP lead to activation of PKG, which then predominates over the PKA effect (ie, cross activation of PKG by cAMP). Similar findings have been recently reported in colonic smooth muscle cells. 3 In smooth muscle cells from the basilar artery, it has been shown that exposure of inside-out patches to the catalytic subunit of PKA increased L-type Ca 2ϩ channel availability. 4 In apparent conflict with these results, Sperelakis and coworkers [11][12][13] have