The 29 amino acid peptide galanin (GAL) coexists with norepinephrine in rat locus coeruleus (LC) neurons to a remarkably high degree. The effects of central administration of GAL were examined in three behavioral paradigms that putatively involve increases in the activity of LC neurons. GAL did not affect behavioral signs associated with naloxone-precipitated withdrawal in rats treated chronically with morphine, a condition in which the firing rate of LC neurons is dramatically increased, although the behavioral signs of withdrawal were abolished by clonidine. Foot shock induced freezing behavior was similarly unaffected by either dose of GAL but was significantly diminished by clonidine and the corticotropin-releasing factor (CRF) antagonist alpha-helical CRF. GAL did not influence the decrease in exploratory activity in a novel open field induced by idazoxan. The behavioral activity of the peptide and route of administration were confirmed in a feeding paradigm. Doses of GAL that were inactive in the three paradigms were active in stimulating intake of a palatable food to a similar degree as clonidine-stimulated intake. These results suggest that intraventricularly administered GAL may not influence behaviors thought to be mediated by activation of neurons in the LC.
- Morphine withdrawal
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience