Effects of intraventricular dynorphin treatment on brain monoamines

Dynorphin was administered into the lateral cerebral ventricle of rats and its effects were measured 60 min later on the noradrenaline (NA), dopamine (DA) and serotonin (5-HT) contents of various brain regions. Dynorphin decreased the NA, DA and 5-HT contents of the hypothalamus as well as the 5-HT content of the caudate nucleus. These effects were not manifested after naloxone pretreatment. In the frontal cortex and in the septum, dynorphin caused a naloxone-insensitive increase in the 5-HT content, and the increased caudate DA content was not antagonized by the opiate receptor antagonist either. The data suggest that dynorphin affects cerebral monoaminergic neurotransmission. The changes of the largest magnitude occured in the hypothalamus. Only some of these effects were antagonized by naloxone, suggesting that the CNS effects of dynorphin are only partly mediated by endogenous opioid binding sites.