The pharmacological properties of voltagedependent calcium channel (VDCC) subtypes appear mainly to be determined by the ␣ 1 pore-forming subunit but, whether P-and Q-type VDCCs are encoded by the same ␣ 1 gene presently is unresolved. To investigate this, we used IgG antibodies to presynaptic VDCCs at motor nerve terminals that underlie muscle weakness in the autoimmune LambertEaton myasthenic syndrome (LEMS). We first studied their action on changes in intracellular free Ca 2؉ concentration [Ca 2؉ ] i in human embryonic kidney (HEK293) cell lines expressing different combinations of human recombinant VDCC subunits. Incubation for 18 h with LEMS IgG (2 mg͞ml) caused a significant dose-dependent reduction in the K ؉ -stimulated [Ca 2؉ ] i increase in the ␣ 1A cell line but not in the ␣ 1B , ␣ 1C , ␣ 1D , and ␣ 1E cell lines, establishing the ␣ 1A subunit as the target for these autoantibodies. Exploiting this specificity, we incubated cultured rat cerebellar neurones with LEMS IgG and observed a reduction in P-type current in Purkinje cells and both P-and Q-type currents in granule cells. These data are consistent with the hypothesis that the ␣ 1A gene encodes for the pore-forming subunit of both P-type and Q-type VDCCs.

Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand gated ion channels, which are found at the neuromuscular junction and in the central and peripheral nervous systems. The channels can be assembled from fourteen known subunits. The exact combination and function of all the channels are still not determined but in the CNS certain combinations have been identified which appear to modulate the release of specific neurotransmitters. Non-specific nAChR agonists like nicotine and epibatidine, have been shown to have interesting pharmacology but their clinical value is limited by their undesirable side effects. Selective ligands for different receptor subtypes have been reported and these compounds are probably the best tools for determining the function of the subtypes. The expectation is that some receptor subtype selective nAChR ligands will be clinically useful for the treatment of a broad range of CNS disorders. The development of stable cell lines functionally expressing specific combinations of subunits has greatly improved our understanding of ligand specificity. There have also been advances in the modelling of the ligand binding site, thanks to the discovery of a homologous snail ACh binding protein the X-ray structure of which was determined in 2001. These techniques should lead to rapid advances in the development of truly subtype selective ligands. In this review we describe recent progress in the area and describe the first 1000 fold selective low molecular weight ligands from the AstraZeneca group. We also comment on the first subtype specific channel modulators.

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Basolateral to apical albumin flux has been measured in sheets of bovine bronchial and tracheal mucosa mounted in vitro. Addition of guinea‐pig peritoneal eosinophils or neutrophils to the basolateral side of such tissues had no significant influence on the transmucosal flux of albumin in either the bronchial or tracheal mucosa. Stimulation of eosinophils or neutrophils by the calcium ionophore A23187, or by their presentation to an opsonized airways mucosa, resulted in a significant increase in the transbronchial flux of albumin. This effect was seen after only 60 min incubation of the leucocytes with the bronchial mucosa, and was no greater when the contact time was extended to 180 min. Incubation of bronchial mucosal tissues with 1 mg ml−1polyarginine for 3 h produced a significant increase in albumin flux, but was ineffective at 0.5 mg ml−1. In contrast to the bronchial mucosa, the tracheal mucosa appeared resistant to the effects of stimulated eosinophils and neutrophils. The lipoxygenase inhibitor AA‐861 failed to influence the ability of eosinophils to augment the transmembrane flux of albumin. However, insertion of a Millipore filter mask between the eosinophils and the bronchial mucosa significantly inhibited the eosinophil‐dependent enhancement of mucosal permeability. The broad spectrum antiproteinase α2‐macroglobulin achieved almost total ablation of the action of stimulated eosinophils in the bronchial mucosa. These results suggest that proteinases may make a significant contribution to the genesis of epithelial injury, whereas leukotrienes do not.