The effect of development of thermoregulatory function on the biochemical assessment of the ontogeny of neonatal dopaminergic neuronal activity.

Previous studies from this laboratory on the functional ontogeny of impulse flow in the nigrostriatal pathway of the neonatal rat were interpreted as indicating that there was an abrupt onset of impulse flow between 6 and 8 days of age. The functional development was assessed by determining the age at which the biochemical responses of these neurons to physical or pharmacological manipulation were similar to those of adult neurons. Further studies of these phenomena demonstrate that the age-dependency of these biochemical markers of impulse traffic are directly related to the development of thermoregulatory function in the neonatal rat. Accordingly, provided that 4-day-old or even younger rats are maintained at or near litter temperature, they exhibit qualitatively all of the biochemical responses characteristic of the 10-day-old or adult animal in which impulse flow is known to be present.