Despite the overwhelming observational evidence supporting the unified scheme of Ac- tive Galactic Nuclei (AGN), there is no compelling reason for AGN constituents to be the same in every AGN. The observed properties of AGN at different wavelengths (from radio to γ-rays) can depend on the location of the respective emitting regions and density and composition of the emitting material. In this dissertation we study the couplings between the emission from the central engine of radio-loud AGN. The main results of this disserta- tion come as follows: (i) The double-peaked emission lines originate most likely in the outer parts of the accretion disk, have been used as tools for studying the structure and dynamics of accretion disk. The distribution of Eddington ratios for a large sample of AGN in the sample has a two component structure peaked at low and high Eddington ratios. The break in the distribution at Lbol/LEdd ∼ 10−3 coincides with the typical Eddington ratio for AGN with broad and double-peaked emission lines. We propose an evolutive scenario where the double-peaked phenomenon is a short-term state transiting between high and low efficiency accreting systems, when the difference between different accretion states manifest itself in a spectral (AGN type) difference between efficient and inefficiently accreting objects. (ii) There is a significant difference in Eddington ratio between radio-quiet and radio-loud AGN with double-peaked Balmer emission lines. In this dissertation, we show that double- peaked emission can be generated as well in an accelerating outflow material located in the radio jet. (iii) We combine for the first time high resolution VLBI monitoring of compact jets with optical continuum observations and study in detail radio-optical correlations in AGN.