Non-axisymmetric gravitational potentials are likely to play an important role in generating central activity in galaxies, i.e. starbursts and/or active galactic nuclei (AGN). For instance, the often observed secondary bars embedded in larger, primary, ones (Friedli & Martinet 1993; Wozniak et al. 1995; Friedli et al. 1996) might play a key role in feeding AGN, by accreting gas down to the centre at scales of a few parsecs. On the other hand, the frequent presence of a nuclear ring of star formation located between both bars indicates that double-barred galaxies are intimately linked to the formation of some circumnuclear starbursts. This type of galaxies might give useful clues to the connection between starbursts and AGN.
Below, as part of a larger sample of nearby barred galaxies (Wozniak et al. 1997a) being taken by ISOCAM on board of the ISO satellite, we briefly discuss the characteristics of the circumnuclear mid-infrared (MIR) emission of two double-barred galaxies, namely NGC 4321 (M100) and NGC 1097. The observations were done using LW2 (5–8.5μm) and LW3 (12–18μm) broad band filters at the 1.5″ px−1 PFOV.