Several studies indicate that systemic GH influences various brain function
s. Connexin-43 forms gap junctions that mediate intercellular communication
and establish the astroglial syncytium. We investigated the effects of per
ipheral administration of bovine GH (bGH) and recombinant human insulin-lik
e growth factor I (rhIGF-I) on the expression of connexin-43 in the rat bra
in. Hypophysectomized female Sprague Dawley rats were substituted with cort
isol (400 mu g/kg.day) and L-T-4 (10 mu g/kg.day) and treated with either b
GH (1 mg/kg .day) or rhIGF-I (0.85 mg/kg.day) for 19 days. The abundance of
connexin-43 messenger RNA (mRNA) and protein in the brainstem, cerebral co
rtex, hippocampus, and hypothalamus was quantified by means of ribonuclease
protection assays and Western blots. Treatment with bGH increased the amou
nts of connexin-43 mRNA and protein in the cerebral cortex and hypothalamus
. No changes were found in the brainstem or hippocampus. Infusion of rhIGF-
I did not affect connexin-43 mRNA or protein levels in any of the brain reg
ions studied. These results show that administration of bGH increases the a
bundance of cx43 in specific brain regions, suggesting that GH may influenc
e gap junction formation and thereby intercellular communication in the bra
in.