Somatostatin (SOM) immunoreactive varicosities and cell bodies are present in the spinal cord. Although SOM immunoreactive cell bodies are evident throughout the gray matter, SOM varicosities are most numerous in the superficial laminae of the dorsal horn and lamina X. Physiological and anatomical studies have suggested that SOM plays a role in various spinal functions including nociception. We hypothesize that SOM plays a role in the processing of somatosensory information, possibly including nociception via undefined spinal circuits. By combining immunohistochemistry to label SOM structures and horseradish peroxidase (HRP) histochemistry to label primary afferents and ascending projection cells in the spinal cord we propose experiments to determine: 1) whether SOM cells and varicosities interact with primary afferents and spinal cord neurons that send ascending projections to nuclei in the brainstem; 2) if specific populations of SOM cells located in the spinal cord send ascending projections to the brainstem. These experiments will provide baseline data for future developmental and experimental studies of spinal SOM systems.
