In 1996 I spent half a year in Bernd Lindemannís laboratory in Homburg/Saar. After attempts to extracellularly record action potentials from fungiform taste papillae in the rat tongue with tungsten electrodes, I switched over to a more established technique, the loose patch recording (Avenet & Lindemann 1991; J. Membrane Biol. 124:33-41). Using a perfused glass electrode, this technique allows recording sustained currents and "action currents" from single taste buds. I investigated responses to stimulation with several tastants included in the perfusion, as well as the effects of inhibitors and enhancers.
After returning to Regensburg in October 1996, I installed a tip recording setup and performed a series of experiments focusing on the spontaneous activity of the olfactory receptor neurons. This work is being continued by Karin Fischer in her master thesis. After additional experiments aiming a more detailed characterization of the spontaneous activity, we are now investigating the time course of adaptation and sensitization.
In early 1997 I started investigating the mechanisms of olfactory transduction and adaptation using the patch clamp technique on cultured Manduca receptor neurons (Stengl & Hildebrand 1990, J. Neurosci 10(3):837-847). The central question of my current work is the effect of cyclic GMP (cGMP) on ion channels involved in the transduction cascade. A slow rise in the cGMP concentration after pheromone stimulation (Ziegelberger et al 1990; J. Neurosci. 10(4):1217-1225) together with a reduction of the pheromone-dependent inositiol trisphosphate formation in elevated cGMP (Boekhoff et al 1993; Insect Biochem. Molec. Biol. 13(7):757-762) strongly suggest an involvement in adaptation. My experiments have revealed several classes of ion channels which are influenced by the application of 8-bromo-cGMP in different ways. While at least one type appears to be activated by a low drug concentration, another type is only weakly influenced, or inactivated by a comparatively high concentration (Dolzer & Stengl 1998; Proc. Göttingen Neurobiol. Conf. 26(II):380). Since the large number of different channel types has made a thorough characterization on the single channel level impossible, future experiments will employ the gramicidin perforated patch technique, looking for blockers of individual current components.
In early 1999 our lab moved to Marburg.