B. Planas et al., GALANIN-BINDING SITES IN THE FEMALE RAT-BRAIN ARE REGULATED ACROSS PUBERTY YET SIMILAR TO THE MALE PATTERN IN ADULTHOOD, Neuroendocrinology, 61(6), 1995, pp. 646-654
The neuropeptide galanin (GAL) has been implicated in a variety of neu
roendocrine functions and has been shown to be regulated by gonadal ho
rmones in several brain regions. We have used slice binding and quanti
tative autoradiography techniques to determine whether the activation
of GAL pathways across puberty in female rats is associated with chang
es in the density of GAL binding in telencephalic and diencephalic reg
ions as we previously observed in male rats. We have also asked whethe
r sex differences in GAL immunoreactivity and GAL gene expression dete
cted in some brain regions would be paralleled by sex differences in I
-125-GAL-binding density in adult male and female rat brains. To contr
ol for intrinsic differences in the level of endogenous GAL synthesis
and release, brain slices from prepubertal female and adult male and f
emale rats were treated with guanosine 5'-triphosphate (GTP) to induce
dissociation of endogenous GAL from its binding sites prior to incuba
tion with radiolabeled ligand. I-125-GAL binding was significantly red
uced in seven brain regions of adult compared with prepubertal female
rats. These regions included the islands of Calleja (p less than or eq
ual to 0.03), the medial amygdaloid nucleus, posterodorsal division (p
less than or equal to 0.05), median eminence (p less than or equal to
0.02), medial habenular nucleus (p less than or equal to 0.05), rhomb
oid thalamic nucleus (p less than or equal to 0.05), and paraventricul
ar (p less than or equal to 0.05) and intermediodorsal (p less than or
equal to 0.02) thalamic nuclei. Only one region, the lateral preoptic
area, exhibited significantly enhanced I-125-GAL binding in adult fem
ale (p less than or equal to 0.04) compared with prepubertal animals.
The distribution and density of I-125-GAL-binding sites were similar i
n adult male and female rat brains and no statistically significant ef
fect of sex or interaction of sex with brain region were detected by A
NOVA. These results suggest that gonadal hormones and/or some other fa
ctors associated with puberty may regulate central GAL receptor number
and/or affinity in discrete regions of the female rat brain. The regi
onal diversity of this regulation suggests that multiple factors are i
nvolved.