Reduction of free fatty acids by acipimox enhances the growth hormone (GH) responses to GH-releasing peptide 2 in elderly men.

GH release is increased by reducing circulating free fatty acids (FFAs). Aging is associated with decreased plasma GH concentrations. We evaluated GH releasing capacity in nine healthy elderly men after administration of GH-releasing peptide 2 (GHRP-2), with or without pretreatment with the antilipolytic drug acipimox, and compared the GHRP-2-induced GH release with the response to GHRH. The area under the curve (AUC) of the GH response after GHRP-2 alone was 4.8 times higher compared with GHRH alone (1834 +/- 255 vs. 382 +/- 78 microg/L.60 min, P: < 0.001). Acipimox, which reduced FFAs from 607 micromol/L to 180 micromol/L, increased the GH AUC to 1087 after GHRH and to 2956 microg/L.60 min after GHRP-2 (P: < 0.01). The AUC after acipimox/GHRP-2 were positively correlated with the AUC after GHRP-2 alone (r = 0.93, P: < 0.01); this was also observed between acipimox/GHRH and GHRH alone (r = 0.73, P: = 0.03). Significant negative correlations were observed between basal FFAs and AUC after GHRH or GHRP-2 after combining the data with and without acipimox (r = 0.58, P: = 0.01 and r = 0.48, P: = 0.04, respectively), and between basal FFAs and GH at t = 0 (r = -0.44, P: = 0.001). Interestingly, GHRP-2 administration was followed by a significant early rise in plasma FFAs by 60% (P = 0.01), indicating an acute lipolytic effect. In conclusion, reduction of circulating FFAs strongly enhances GHRP-2-stimulated GH release in elderly men. The data indicate that the decreased GH release associated with aging can be reversed by acipimox and that the pituitary GH secretory capacity in elderly men is still sufficient.

Prenatal exposure to morphine affects juvenile play behavior and adult social behavior in rats.

The effects of morphine exposure in utero on play behavior and social behavior were investigated in a longitudinal study. Wistar rat dams were SC injected daily with saline (control) or 10 mg/kg morphine from day 8 to day 21 of gestation. Play behavior of the offspring was measured at 3 and 4 weeks of age and social behavior at 3 months of age. Pinning, a measure for play behavior and social grooming of the morphine-treated offspring were significantly elevated compared to saline controls, especially on day 21. The onset-latency of pinning behavior was not changed. Furthermore, prenatal morphine treatment resulted in more social approach and less social avoidance behavior in adulthood, whereas changes in general locomotor activity were not observed. The results are discussed in relation to the effects of in utero exposure of morphine on the development of incentive aspects of play and social behavior.