| Popis: |
Understanding neurotransmission begins with the anatomical and cellular localisation of neurotransmitters and their receptors. Ideally the question to be answered is: which neurone contains which receptor, and where are the receptors localised at the cellular level? It goes without saying that in many cases knowledge of this is only partial; the complexity of the 5-hydroxytryptamine (5-HT; for abbreviations, see “Appendix”) receptor family with its seven subfamilies does not make the task simple (Hoyer et al. 1994). Fortunately, however, a number of radioligands which became available over the past decade have been used to characterise 5-HT binding sites; all of these sites were eventually recognised as true receptors since the corresponding cDNAs have been cloned. Receptor autoradiography emerged early as the method of choice to map brain receptors; it is indeed very gratifying to actually “see” the receptors labelled with a radioligand in many brain areas and nuclei, something that would simply be impossible to achieve using dissection techniques combined with membrane binding. However, there are a number of limitations to this methodology, which relate (a) to the potential lack of selectivity of the radioligands used (if at all available) and (b) to the technique, which in principle does not allow resolution at or below the cellular level. |
