Smelling Sounds: Olfactory-Auditory Sensory Convergence in the Olfactory Tubercle

Early events in the evolutionary history of a clade can shape the sensory systems of descendant lineages. Although the avian ancestor may not have had a sweet receptor, the widespread incidence of nectar-feeding birds suggests multiple acquisitions of sugar detection. In this study, we identify a single early sensory shift of the umami receptor (the T1R1-T1R3 heterodimer) that conferred sweet-sensing abilities in songbirds, a large evolutionary radiation containing nearly half of all living birds. We demonstrate sugar responses across species with diverse diets, uncover critical sites underlying carbohydrate detection, and identify the molecular basis of sensory convergence between songbirds and nectar-specialist hummingbirds. This early shift shaped the sensory biology of an entire radiation, emphasizing the role of contingency and providing an example of the genetic basis of convergence in avian evolution.

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Electrophysiological characterization of laminar synaptic inputs to the olfactory tubercle of the rat studiedin vitro: modulation of glutamatergic transmission by cholinergic agents is pathway-specific

European Journal of Neuroscience ◽

10.1046/j.0953-816x.2001.01556.x ◽

2001 ◽

Vol 13 (9) ◽

pp. 1767-1780 ◽

Cited By ~ 10

Author(s):

G. S. Owen ◽

J. V. Halliwell

Keyword(s):

Olfactory Tubercle ◽

Glutamatergic Transmission ◽

Synaptic Inputs ◽

Cholinergic Agents ◽

Electrophysiological Characterization

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The glycosylation properties of D2 dopamine receptors from striatal and limbic areas of bovine brain

Biochemical Journal ◽

10.1042/bj2550877 ◽

1988 ◽

Vol 255 (3) ◽

pp. 877-883 ◽

Cited By ~ 9

Author(s):

M N Leonard ◽

R A Williamson ◽

P G Strange

Keyword(s):

Caudate Nucleus ◽

Dopamine Receptors ◽

Sodium Cholate ◽

Bovine Brain ◽

Affinity Column ◽

Olfactory Tubercle ◽

D2 Dopamine Receptors ◽

Neuraminidase Treatment ◽

Membrane Bound ◽

Affinity Interaction

D2 dopamine receptors from bovine brain (caudate nucleus and olfactory tubercle) have been solubilized using sodium cholate/NaCl and their glycoprotein properties studied in terms of their interaction with wheat-germ agglutinin-agarose (WGA-agarose). Under optimal conditions about 65% of the applied D2 dopamine receptors bound to WGA-agarose and could be eluted with N-acetylglucosamine. The ability of receptors to adsorb to the affinity column was shown to be dependent on the cholate and salt concentrations used. Digestion of the membrane bound D2 dopamine receptors with neuraminidase prior to solubilisation reduced the ability of the receptors to bind to WGA-agarose (50% of applied receptors bound) whereas digestion with N-acetylglucosaminidase did not significantly affect binding to WGA-agarose. Digestion with the two enzymes together resulted in a larger decrease in binding to WGA-agarose than was seen with the two enzymes alone (40% of applied receptors bound). Stepwise elution of bound receptors from the WGA-agarose columns using 2.5 mM- and 100-mM-N-acetylglucosamine showed that about 40% of the bound receptors interacted with WGA-agarose in a low-affinity manner, the remainder showing a high-affinity interaction. Neuraminidase treatment reduced the low-affinity population suggesting that the interaction of oligosaccharides bearing sialic acid with WGA-agarose is of lower affinity and that higher-affinity binding is via N-acetylglucosamine. These data are discussed in terms of the heterogeneity of carbohydrate moieties on the D2 dopamine receptors within a brain region. In all the tests applied here, however, receptors from caudate nucleus and olfactory tubercle behaved identically so their glycosylation patterns must be very similar.

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