Evidence for endogenous inhibition of autotomy by galanin in the rat after sciatic nerve section: demonstrated by chronic intrathecal infusion of a high affinity galanin receptor antagonist.

We have studied the effect of M-35 [Galanin(1-12)-Pro-bradykinin(2-9)-amide], a newly developed high affinity antagonist for galanin receptors, on self-mutilation (autotomy) behavior of the deafferented limb in rats after unilateral section of sciatic nerves. M-35 (1.3 micrograms/microliters) or saline was applied to the lumbar spinal cord through a chronically implanted intrathecal catheter at a rate of 0.5 microliter/h for 10 days post axotomy via an osmotic minipump. Axotomized rats infused with M-35 autotomized significantly more than those perfused intrathecally with saline or those axotomized rats not implanted with an intrathecal catheter. The severity of autotomy was also markedly greater in the group treated with M-35 than in the two other groups. M-35 did not noticeably influence either the galanin mRNA level in corresponding dorsal root ganglia and dorsal horn region or the percent of lumbar sensory neurons expressing detectable levels of mRNA for galanin. It is suggested that galanin can endogenously suppress autotomy behavior in rats after nerve injury and thus may play an important role in the control of the development of neuropathic pain.