Varenicline decreases ethanol intake and increases dopamine release via neuronal nicotinic acetylcholine receptors in the nucleus accumbens.

BACKGROUND AND PURPOSE: Varenicline, a neuronal nicotinic acetylcholine receptor (nAChR) modulator, decreases ethanol consumption in rodents and humans. The proposed mechanism of action for varenicline to reduce ethanol consumption has been through modulation of dopamine (DA) release in the nucleus accumbens (NAc) via α4*-containing nAChRs in the ventral tegmental area (VTA). However, presynaptic nAChRs on dopaminergic terminals in the NAc have been shown to directly modulate dopaminergic signalling independently of neuronal activity from the VTA. In this study, we determined whether nAChRs in the NAc play a role in varenicline's effects on ethanol consumption. EXPERIMENTAL APPROACH: Rats were trained to consume ethanol using the intermittent-access two-bottle choice protocol for 10 weeks. Ethanol intake was measured after varenicline or vehicle was microinfused into the NAc (core, shell or core-shell border) or the VTA (anterior or posterior). The effect of varenicline treatment on DA release in the NAc was measured using both in vivo microdialysis and in vitro fast-scan cyclic voltammetry (FSCV). KEY RESULTS: Microinfusion of varenicline into the NAc core and core-shell border, but not into the NAc shell or VTA, reduced ethanol intake following long-term ethanol consumption. During microdialysis, a significant enhancement in accumbal DA release occurred following systemic administration of varenicline and FSCV showed that varenicline also altered the evoked release of DA in the NAc. CONCLUSION AND IMPLICATIONS: Following long-term ethanol consumption, varenicline in the NAc reduces ethanol intake, suggesting that presynaptic nAChRs in the NAc are important for mediating varenicline's effects on ethanol consumption.

Fossils and avian evolution.

Discoveries of archaic Mesozoic fossil birds ('opposite' birds, or enantiornithines) during the past decade have revolutionized our understanding of early avian evolution, but the rarity of Early Cretaceous ornithurines - birds that are closely related to the modern avian radiation - has meant that information about these species has lagged behind.

Nonavian feathers in a late Triassic archosaur.

Longisquama insignis was an unusual archosaur from the Late Triassic of central Asia. Along its dorsal axis Longisquama bore a series of paired integumentary appendages that resembled avian feathers in many details, especially in the anatomy of the basal region. The latter is sufficiently similar to the calamus of modern feathers that each probably represents the culmination of virtually identical morphogenetic processes. The exact relationship of Longisquama to birds is uncertain. Nevertheless, we interpret Longisquama's elongate integumentary appendages as nonavian feathers and suggest that they are probably homologous with avian feathers. If so, they antedate the feathers of Archaeopteryx, the first known bird from the Late Jurassic.

Early Adaptive Radiation of Birds: Evidence from Fossils from Northeastern China

Late Jurassic and Early Cretaceous birds from northeastern China, including many complete skeletons of Confuciusornis, provide evidence for a fundamental dichotomy in the class Aves that may antedate the temporal occurrence of the Late Jurassic Archaeopteryx. The abundance of Confuciusornis may provide evidence of avian social behavior. Jurassic skeletal remains of an ornithurine bird lend further support to the idea of an early separation of the line that gave rise to modern birds. Chaoyangia, an ornithurine bird from the Early Cretaceous of China, has premaxillary teeth.

Evidence from claw geometry indicating arboreal habits of archaeopteryx.

The Late Jurassic Archaeopteryx has been thought to have been a feathered predator adapted to running that represented a terrestrial stage in the evolution of true birds from coelurosaurian dinosaurs. Examination of claw geometry, however, shows that (i) modern ground- and tree-dwelling birds can be distinguished on the basis of claw curvature, in that greater claw arcs characterize tree-dwellers and trunk-climbers, and (ii) the claws of the pes (hind foot) and manus (front hand) of Archaeopteryx exhibit degrees of curvature typical of perching and trunk-climbing birds, respectively. On this basis, Archaeopteryx appears to have been a perching bird, not a cursorial predator.

Feathers of archaeopteryx: asymmetric vanes indicate aerodynamic function.

Vanes in the primary flight feathers of Archaeopteryx conform to the asymmetric pattern in modern flying birds. The asymmetry has aerodynamic functions and can be assumed to have evolved in the selective context of flight.