EFFECT OF TACTILE STIMULATION ON SERUM LACTATE IN THE NEWBORN RAT

Maturation of the CNS in neonatal animals is dependent upon both senso ry input and the constant availability of metabolic fuel. Previous rep orts indicate that the preferred metabolic substrate for the developin g rat brain is lactate. In this study, we used the neonatal Sprague-Da wley rat to investigate a possible interactive role between touch and the regulation of serum lactate. Two hundred and fifty rats (postnatal d 0-7) were exposed to a standard tactile stimulation (TS) regimen to mimic nonspecific maternal stimulation. This regimen consisted of str oking the dorsum with a soft camel hair brush for 30 s every minute fo r 10 min. Serum lactate and glucose levels were measured after TS. In newborn (d 0) rats, lactate levels were increased by 207% in stroked p ups versus controls. This elevation of serum lactate persisted for 30 min after cessation of TS, On d 7, TS increased lactate only 11%. Gluc ose levels were unaffected at all ages. In neonatal pups, pretreatment with pentobarbital blocked the effect of TS, whereas epidermal growth factor evoked a synergistic response. Capsaicin pretreatment had no e ffect. Mixed arteriovenous blood gases revealed a mild increase in pH and a decrease in PCO2 after TS. We conclude that TS in newborn rats i s a regulator of circulating lactate. This response is maximal in the immediate postnatal period and wanes over the Ist wk of life. We specu late that the transduction of sensory signals by the skin is a mechani sm regulating the availability of cerebral energy substrates in the ne wborn mammal.