Effects of immunoneutralization of dynorphin 1–17 and dynorphin 1–18 on the activity of central dopaminergic neurons in the male rat

Abstract

The effect of administration of antibodies against dynorphin 1–17 (DYN 1–17-AB) and dynorphin 1–N(DYN 1–N-AB) were examined on the activity of dopaminergic (DA) neurons comprising the nigrostriatal, mesolimbic, tuberoinfundibular and periventricular-hypophysial systems in the male rat brain. DA neuronal activity was estimated by measuring the concentration of the dopamine metabolite 3,4-dihydrophenylacetic acid (DOPAC) in brain (striatum, nucleus accumbens, median eminence) and pituitary regions (intermediate lobe) containing terminals of these neurons. The intracerebroventricular administration of either DYN 1–17-AB or DYN 1–N-AB produced a time-related increase in the activity of tuberinfundibular and periventricular-hypophysial DA neurons, but failed toalter the activity of nigrstriatal or mesolimbic DA neurons. The ability of both DYN 1–17-AB to endhance of tuberofundibular and periventricular-hypophysial DA neurons was reversed by the kappa opioid ag50,488. These results indicate that 1–17-AB and and DYN 1-N-AB, presumably by binding endogenous dynorphins, remove a tonic inhibitory action of these opioid peptides on tuberoinfundibular and periventricular-hypophysial DA neurons.