Submitted March 25, 2002
Returned for revision April 10, 2002
Accepted August 7, 2002
Pitutitary
Testosterone-Dependent Effects of Galanin on Pituitary
Luteinizing Hormone Secretion in Male Rats
Joseph R. Scheffen 1,
Cynthia L. Splett 1,
Joshua A Desotelle 1,
Angela C. Bauer-Dantoin 1*
1 University of Wisconsin
* To whom correspondence should be addressed. E-mail: bauera{at}uwgb.edu.
Abstract
Galanin is a 29-amino acid peptide that colocalizes with
GnRH in hypothalamic neurons. High concentrations of
galanin are present in portal vessel blood of both male
and female rats, and galanin receptors are present on
gonadotropes in both sexes. Results from studies in female
rats indicate that galanin acts at the level of the
pituitary to directly stimulate LH secretion and also
enhance GnRH-stimulated LH secretion. The effects of
galanin on pituitary LH secretion in male rats are
relatively uncharacterized, and thus the following in vivo
study was conducted to 1) examine the ability of galanin
to affect basal or GnRH-stimulated LH secretion in male
rats and 2) determine whether the effects of galanin on LH
secretion in males are testosterone-dependent. All three
doses of galanin used in the study (1, 5 and 10
µg/pulse) significantly enhanced GnRH-stimulated LH
secretion in intact male rats. Only the highest dose of
galanin directly stimulated LH secretion (without GnRH
coadministration) in intact male rats. Galanin did not
directly stimulate LH secretion or enhance GnRH-stimulated
LH secretion in castrated males. In fact, the highest dose
of galanin inhibited GnRH-stimulated LH secretion in
castrated males. Upon testosterone replacement, the
ability of galanin to directly stimulate LH secretion and
enhance GnRH-stimulated LH secretion was restored in
castrated males. These results suggest a role for galanin
in the regulation of LH release in males and demonstrate
that testosterone upregulates the ability of the pituitary
to respond to the stimulatory effects of galanin.
Key words:
Male Reproductive Tract •
Pituitary •
Galanin •
Gonadotropin-releasing hormone •
Luteinizing hormone
