Gestational Changes in Calcitonin Gene-Related Peptide, Nerve Growth Factor, and Its Receptors in Rat Dorsal Root Ganglia1

Abstract

In dorsal root ganglia (DRG) cell cultures, levels of calcitonin gene-related peptide (CGRP) are increased in the presence of ovarian hormones and nerve growth factor (NGF). In addition, injection of ovariectomized rats with ovarian hormones led to an increase in levels of two NGF receptors, TrkA and p75(NTR), in DRG. Thus, we hypothesized that increased levels of ovarian hormones during pregnancy may elevate the synthesis of CGRP and NGF receptors in the DRG. DRG harvested from rats on specific days of pregnancy, on Day 2 postpartum, and after ovariectomy were subjected to radioimmunoassay, Western blot analysis, and NGF immunoassay to determine levels of CGRP, TrkA and p75(NTR), and NGF, respectively. CGRP levels in rat DRG were significantly higher during pregnancy than at Day 2 postpartum or in ovariectomized rats. Levels of both TrkA and p75(NTR) in DRG increased during pregnancy and remained elevated at Day 2 postpartum, but CGRP levels declined. Levels of NGF reached a statistically significant peak at Day 18 of gestation, and were not significantly reduced at Day 2 postpartum. Increased levels of ovarian steroid hormones during pregnancy may be involved in the synthesis of CGRP, however, the postpartum decreases in CGRP synthesis appear to be unrelated to NGF and its receptors.

Dietary isoflavone increases insulin-like growth factor-I production, thereby promoting hair growth in mice

“…Consistent with this hypothesis are observations in the present study demonstrating that administration of isoflavone increased the dermal levels of IGF-I and IGF-I mRNA levels in WT mice but not CGRP −/− mice. Since estrogen has been shown to increase the CGRP levels in sensory neurons by enhancing NGF-mediated production of CGRP [20,34,35], isoflavone is referred to as phytoestrogen.…”

Expression of calcitonin gene-related peptide in anterior and posterior horns of the spinal cord after brachial plexus injury

“…14 The CGRP expression in neurons can be increased by lowpower laser irradiation, and application of neurotrophic factors in vitro 15,16 or in vivo, 17 promoting neural regeneration. CGRP applied alone or combined with neurotrophic factors can protect the neurons of rats with ischemic injury, and are synergistic with the neurotrophic factors.…”

Plasticity in developing rat uterine sensory nerves: the role of NGF and TrkA

“…This possibility is reinforced by studies showing that oestrogen leads to alterations in the expression of NGF receptors in adult sensory neurons (Sohrabji et al 1994;Liuzzi et al 1999). In addition, sex hormoneinduced upregulation of CGRP synthesis in female DRG neurons is mediated by NGF (Gangula et al 2000) and involves alterations in the neuronal receptivity to neurotrophins (Lanlua et al 2001a(Lanlua et al , 2001b. Neuronal responsiveness to NGF is mediated by two receptors: TrkA, a member of the family of tyrosine kinase receptors, and p75 NTR , a member of the tumour-necrosis factor receptor superfamily (Frade and Barde 1998).…”