Muscarinic receptors in airways diseases

Abstract

It was with some trepidation that I undertook the task of reviewing this book. After all what new could be said about the use of agents which have their origin before recorded time and are almost certainly the oldest drugs to be used in respiratory medicine. In fact, this book is an absolute delight and kept me entertained and stimulated throughout what would have been a very tedious flight. The key to understanding the book's success is in the title of the series rather than the volume. Muscarinic Receptors in Airways Disease is published in the Progress and Inflammation Research Series. The volume does not contain a detailed exposition of the effect of the cholinergic nervous system in bronchoconstriction but rather concentrates on other aspects of muscarinic responses, particularly as one might expect in the field of inflammation. The editors have gathered together a distinguished group of authors who are quite clearly giving of their best in each chapter. The volume starts with a super exposition of the parasympathetic mechanisms by Unden & Myers. In this and virtually every other chapter there was an important concept which was new (at least to me). I had not realized that the efficiency of synaptic transmission varies between different junctions. The so called axo-dendritic synapse or the axo-somatic synapses differ greatly in their efficiency of transmission and because of the relatively low efficiency of airways ganglia there is very great opportunity for modulation of synaptic transmission by external forces, either neuronal or inflammatory. In the next chapter Wessler & Kirkpatrick introduced me to non-neuronal acetylcholine in the airways, a concept that I had not thought about deeply but it is expounded with great lucidity. This chapter along with virtually every other is extensively referenced with nearly 200 citations. The next four chapters deal with the muscarinic receptors, their localization and regulation. Refreshingly the non-constricting M2 receptor is highlighted and I came away thinking that this was an important target potential for new drugs. Peter Barnes does his usual lucid instruction on the gene regulation of muscarinic receptors. The final part of the book on the clinical pharmacology I found to be the weakest, perhaps because of the previous very high standard of writing. Having said that, Kenneth Chapman is given the thankless task of reviewing previous anticholinergic therapy in asthma and COPD and responds with a superb opening few pages on the long and fascinating history of anticholinergic therapy. The final chapter on a novel perspective of anticholinergic therapy I found disappointing and not entirely up to date. This is particularly a shame since Bernd Disse could have given us greater insight on what could be a very exciting drug, tiotropium. Overall I would highly recommend this volume. It is a must for anyone interested in the nervous control of the airways and I am sure I will be referring to it again and again. It has made me go back and look at the study on which the M2 regulation of neurogenic bronchoconstriction is based. The entire edifice is built on the response of seven normal volunteers! Finally, I was saddened but not surprised to see that in a book of 260 pages the commonest respiratory symptom, which is almost entirely neurogenic, was mentioned only in passing, yet cough accounts for more consultations than any other respiratory disease put together.