Tom Finger, Ph.D.

Development and Organization of the Chemical Senses

The chemical senses, including taste, smell and trigeminal sensitivity, play an important role in social and ingestive activities of all animals. A major emphasis in my laboratory is on questions concerning the development and organization of these systems in several vertebrate models. Three major areas are under investigation at present: 1) morphology and function of solitary chemosensory cells (see Finger et al. PNAS 2003) in protection of the airways and gut, 2) the cellular organization and development of taste buds (see Finger et al, Science 2005, and 3) regulation of feeding behavior by taste and other oropharyngeal chemoreceptors.

Solitary Chemosensory Receptor Cells are situated in the respiratory epithelium of the nasal cavity and make contact with sensory fibers of the trigeminal nerve. These chemoreceptor cells utilize diverse receptor mechanisms to detect noxious substances in the incoming airstream and elicit protective reflexes such as sneezing, coughing or cessation of inspiration (apnea). We are investigating how these cells differentiate from epithelial basal cells and how they detect the presence of noxious substances.

Taste buds consist of short, neuroepithelial receptor cells embedded in gustatory epithelia, e.g. of the tongue, palate and larynx. We have ​shown that taste buds consist of 3 distinct differentiated cell types each serving a distinct function (Yee et al., 2001; Bartel et al, 2006). Our lineage analysis in transgenic mice, shows that taste buds arise from local epithelium and originate from a handful of epithelial progenitors (Stone et al. 1995). Our current experiments examine the role of each type of cell in detection of different taste qualities.

Feeding behavior is regulated largely by gustatory cues in many vertebrates. In order for a potential foodstuff to be swallowed, it must trigger an appetitive gustatory cue. Taste buds release ATP to activate the gustatory nerves and genetic elimination of ATP receptors (P2X2 and P2X3) on the gustatory nerves results in a mouse unable to taste anything (Finger et al 2005). Yet these animals maintain normal weight and can still react when they ingest certain substances. We are investigating the role of taste and non-taste chemoreceptors in the oropharynx and gut in regulation of food intake in these “tasteless” mice (Hallock et al, 2009).

We also use non-mammalian models to study central processing and transmission of taste information. Goldfish have evolved an elaborate specialization of the pharynx that is involved in sorting food from substrate (Lamb & Finger 1995; Sharp & Finger, 2002). The neuronal machinery involved in this behavior is situated in an easily accessible, laminated structure of the hindbrain. This organization is conducive to in vitro slice physiology and pharmacology as well as to in Ca++ imaging studies on synaptic transmission (Ikenaga et al. 2009).