The autoradiographic 2-deoxyglucose method for regional cerebral metabolic activity was modified for use with tritium label to determine which brain stem and spinal cord nuclei changed their functional neural activity during periaqueductal gray stimulation-produced analgesia. The greatest changes in activity during electrical stimulation of the periaqueductal gray occurred in nucleus paragigantocellularis, the ventral portion of the nucleus reticularis gigantocellularis, and the nucleus cuneiformis. Substantial increases in metabolic activity were also evident in the spinal trigeminal nucleus and the substantia gelatinosa. Many of the regions which displayed increased functional activity in the present study have been shown to possess substantial enkephalin immunoreactivity. While several of these structures have previously been implicated in modulation of nociceptive transmission, this study raises the possibility that other brain stem nuclei may also participate in analgesic mechanisms.
Bibliographical noteFunding Information:
Supported by NSF BNS 790 6486, USC RPSC, AHA, and NIH S08 RR09093. The expertise of Dr. Michael Huhns and the image analysis laboratory of the USC College of Engineering and the technical assistance of Helen Fennell, Stu Snyder, and Dick Wells are gratefully appreciated.
- 2-deoxyglucose autoradiography
- Metabolic activity
- Periaqueductal gray
- Regional brain activity