Modification of hypothalamic content of growth hormone regulatory peptides in maternally deprived neonatal rats.

The possibility that maternal deprivation (MD) modifies growth hormone releasing hormone (GHRH) and/or growth hormone release inhibiting hormone (GHRIH) in 10-day-old rat pups was investigated by quantifying the total hypothalamic content of these two hormones which regulate the release of growth hormone (GH), since MD has previously been shown to suppress circulating GH levels. At 10 days of age, rat pups were maternally deprived for either 1 or 6 hours (control pups remained with their mother while littermates were deprived). At the end of the time period, hypothalami were dissected free, homogenized, frozen, and then lyophilized. Reconstituted extracts were later subjected to radioimmunoassay for GHRH and GHRIH. Tests for differences in the brain content of the hormones were performed by analysis of variance; multiple comparison of the means was performed using Tukey's test. A significant increase in the GHRIH content was observed in the hypothalami of maternally deprived rats as compared to control animals (P = 0.026). Small differences in the mean GHRIH content between the different experimental groups suggested a trend toward elevation of GHRIH after either 1 or 6 hours of MD and a trend toward higher levels in males as compared to females (P = 0.0636). No differences in hypothalamic GHRH content were found between maternally deprived and control pups (175.8 pg/hypothalamus vs. 171.5 pg/hypothalamus). The modification of GHRIH hypothalamic content during MD of neonatal rats demonstrated in the present study may be related to the suppression of GH that is known to result from MD.