1. ¹Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC, USA
2. ²Department of Medicine, Duke University Medical Center, Durham, NC, USA

Correspondence: Dr SM Schanberg, Department of Pharmacology and Cancer Biology, Duke University Medical Center, Box 3813, Durham, NC 27710, USA. Tel: +1 919 684 5187; E-mail: schan003@mc.duke.edu

Received 3 August 2001; Revised 28 September 2001; Accepted 26 November 2002; Published online 9 April 2003.

Abstract

During short-term periods of separation of rat pups from their mothers, the loss of certain sensory signals suppresses the increase in ornithine decarboxylase (ODC) gene expression induced by the growth-promoting hormones prolactin (PRL) and growth hormone (GH). Here, we identify a molecular mechanism through which maternal separation (MS) curtails ODC expression. Our results demonstrate that the absence of specific tactile stimuli provided by the mother limits PRL-evoked stimulation of ODC biosynthesis by interfering with sn-1,2-diacylglycerol's (DAG) ability to activate protein kinase C (PKC) and consequently c-myc mRNA and max mRNA expression. The proteins encoded by these proto-oncogenes function as direct transactivators of the ODC gene. As ODC activity is obligatory for normal cell replication and differentiation, PKC activation by DAG represents an important control point at which 'nurturing touch' regulates growth and development of the neonate. Such a mechanism can explain the maladaptive consequences of disrupting mother–infant tactile interactions as occurs in isolated premature babies. Also, it could provide a basis for developing therapeutic interventions to maximize growth potential in children failing-to-thrive despite normal maternal care.