Addiction

Covalent modification of proteins by cocaine.Deng, S.-X. et al. Proc. Natl Acad. Sci. USA 99, 3412–3416 (2002)

As the methyl ester group of cocaine is extremely labile, Deng et al. tested whether it could react with chemical groups on proteins, and found that cocaine reacts specifically with the amino group of lysine residues in vitro. Also, the plasma of rats and humans that were chronically exposed to the drug contained covalently modified proteins. This modification might explain the autoimmune effects of cocaine, and some of its long-term actions on the brain.

Sensory systems

A single olfactory receptor specifically binds a set of odorant molecules.Gaillard, I. et al. Eur. J. Neurosci. 15, 409–418 (2002)

Although a large family of olfactory receptors has been found, their ligands have not been identified. Gaillard et al. report on a calcium-imaging-based screening procedure that might assist in the identification of specific odorants. The authors validated this system by identifying the structural motifs of ligands that bind to the mouse olfactory receptor 912-93, and found that it was activated by aliphatic ketones. This system might help in the functional characterization of the olfactory receptors.

Development

The bHLH transcription factors OLIG2 and OLIG1 couple neuronal and glial subtype specification.Zhou, Q. & Anderson, D. J. Cell 109, 61–73 (2002)

This and a related paper by Lu et al. in the same issue of Cell shed light on the function of Olig1 and Olig2 in cell specification in the spinal cord. In wild-type embryos, these transcription factors are expressed in a region that gives rise sequentially to motor neurons and oligodendrocytes. Zhou and Anderson generated Olig1/2 double-mutant mice and found that both cell types were absent in these animals. Instead, the mutant progenitor cells gave rise to interneurons and then astrocytes, indicating that Olig1/2 do not control the neuron–glia decision, but act to couple neuronal and glial specification.

Synaptic physiology

Evidence for two distinct processes in the final stages of neurotransmitter release as detected by binomial analysis in calcium and strontium solutions.Searl, T. J. & Silinsky, E. M. J. Physiol. (Lond.) 539, 693–705 (2002)

The authors analysed transmitter release at the frog neuromuscular junction in solutions that contained calcium or strontium. They found that the values of the quantal parameters n (the number of releasable quanta) and p (the release probability) depended on the divalent cation. Statistical analyses led them to suggest the existence of two different steps in the final stages of exocytosis. It will now be important to test whether these steps are subserved by specific presynaptic proteins.