Abstract
The binding of 3H-labeled L-quinuclidinylbenzilate (QNB) sites was studied in cryosections of the rat spinal cord (cervical, thoracic and lumbar cords) by in vitro macroautoradiography in an attempt to elucidate the distribution of muscarinic cholinergic (mACh)receptors. In this study, transverse sections as well as longitudinal sections of the thoracic cord were employed. A moderately high density of QNB binding sites could be seen in the gray matter of the spinal cord, especially in the marginal regions of the dorsal horn and around motor neurons in the ventral horn. In the lateral horn of the thoracic cord, a moderately high density of QNB binding sites was segmentally observed. By image analysis with a RAS 1000 (Amersham), color coded autoradiographic images which enhanced the small differences in optical density could be easily obtained, and quantitative analysis of the QNB binding sites in small-sized regions of the spinal cord was also performed. The highest densities of mACh receptors in the spinal cord were localized in the substantia gelatinosa of the dorsal horn and the region of motor neurons of the ventral horn. These findings suggest that while mACh receptors are related with motor functions, they are deeply related with sensory and autonomic functions.
