James, Sharon; (1990) Autoradiographic localization of receptors in the periphery. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis is primarily concerned with the autoradiographic localization of receptors for neurotransmitters or neuromodulators within the autonomic nervous system. In particular, it deals with the regional and cellular localization of alpha-adrenoceptors, muscarinic cholinergic, δ-opioid, substance P and atrial natriuretic peptide receptors either on morphologically or immunocytochemically identified targets. An in vitro autoradiographic approach has been used to establish the regional localization of receptors in tissue sections from both human benign hyperplastic prostate and sigmoid colon specimens. With the aid of image analysis, it was established that there was an abundance of alpha-1 adrenoceptors in the prostatic stromal compartment in comparison with alpha-2 adrenoceptors, whereas muscarinic receptors were almost exclusively epithelial. δ-opioid binding sites were demonstrated in the human colon using [3H][D-Ala2,D-Leu5] enkephalin and it was shown that the greatest density of binding was associated with neurones in the myenteric plexus, situated between the longitudinal and circular muscle layers. The overall distribution and density of δ-opioid binding sites appeared to be similar on tissue sections from patients suffering from chronic constipation and from sections of uninvolved colon from patients with rectal cancer. In order to examine the immunocytochemical nature and receptor expression of individual cell types, culture preparations from the rat superior cervical ganglion, guinea-pig urinary bladder, rat trachea, rat and guinea-pig atria and ventricles and rat sympathetic chain were examined. A proportion of the intramural neurones present within the guinea-pig urinary bladder wall contained neuropeptide Y (NPY) and dopamine B-hydroxylase (DBH) both in situ and in culture. Furthermore, NPY-like immunoreactivity was colocalized with either somatostatin (SOM)- or DBH-like immunoreactivity in subpopulations of cultured intramural bladder neurones. Peptide and muscarinic receptors were localized in several different culture preparations and, where identification based on cell morphology alone was ambiguous, the cultures were concurrently labelled by immunocytochemistry either to confirm their cellular identity or to demonstrate their neurochemical content. Muscarinic receptors were localized on cultured vasoactive intestinal polypeptide (VIP)- and NPY-like immunoreactive neurones from newborn rat superior cervical ganglia. Likewise, SOM-like immunoreactive neurones of the guinea-pig bladder and a large proportion of rat paratracheal neurones also expressed muscarinic receptors in culture. In contrast to the neuronal localization of substance P and muscarinic receptors, it was evident that atrial natriuretic peptide receptors were situated on subpopulations of immuno-cytochemically-identified non-neuronal cells in cultures from rat and guinea-pig hearts and rat sympathetic ganglia.

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