Firing patterns of inferior colliculus neurons-histology and mechanism to change firing patterns in rat brain slices.

An in vitro slice preparation was used for intracellular recording from rat central nucleus of inferior colliculus neurons (CNIC). Stable intracellular recordings were made on 184 neurons, 27 of which were successfully stained with iontophoresed biocytin. Twenty one of those were classified as flat (F), four as less flat (LF) and the remaining two neurons as unclassified neurons. Recording in response to depolarizing current steps revealed five firing patterns: onset, adapting (regularly and irregularly), regular and bursting. The onset neurons showed non-linear current-voltage (I-V) relationship, whereas the rest had linear current-voltage relationship. Preconditioning hyperpolarizations changed the response pattern of CNIC neurons. It is concluded that there is no anatomy and physiology correlation and the levels of membrane potential may be important in the production of some firing patterns.