Neurotensin has been demonstrated to be analgesic in rodents. This study used intrathecal injection of neurotensin in unanesthetized mice to evaluate the effect of the peptide at the spinal level on unconditioned behavior. Intrathecal administration of neurotensin produced dose-related inhibition of locomotor activity and of the response elicited by subcutaneous hypertonic saline. The effects of the peptide in the tail flick assay were variable and it produced no inhibition of the behavioral response to intrathecal substance P. The results indicate that neurotensin antinociception at the spinal level does not result from locomotor impairment, may be somewhat selective for chemically induced pain, and may be mediated by a presynaptic action on primary afferent fibers.
Bibliographical noteFunding Information:
The SP behavioral assay consisted of injecting 10 ng SP (6,5 pmol) IT and counting the number of caudally-directed biting and scratching responses for 1 min immediately fol- ~This work was supported by U.S. Public Health Grants DA 01933, T32GM07397 and RR 05385 and by a grant from the Proctor and Gamble Company. 2Requests for reprints should be addressed to George L. Wilcox.
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- Substance P