Effects of streptozotocin-induced diabetes on dopaminergic functioning in the rat: analysis of yawning behavior.

Apomorphine, a dopamine receptor agonist, causes yawning in rats. It has been suggested that the analysis of yawning behavior provides an index of dopamine autoreceptor function. Dopamine turnover in the substantia nigra of diabetic rats has been shown to be decreased following administration of amphetamine or apomorphine (17,21). Yawning behavior after 4 weeks of streptozotocin (STZ)-induced diabetes in Wistar rats was significantly lowered when compared with their age-matched normal controls. Yawning behavior was not further diminished after an 8-week duration of diabetes mellitus; however, a significant recovery in yawning was seen by 20 weeks of diabetes. Yawning in rats after 20 weeks of STZ-induced diabetes mellitus is not significantly different from that seen in normal control rats. The results suggest that in STZ-induced diabetes of only 4 weeks duration a measurable change in the substrate for yawning has occurred.