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First published online January 27, 2004
Journal of Experimental Biology 207, 715-722 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00809

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Calcium responses of chicken trigeminal ganglion neurons to methyl anthranilate and capsaicin

Michael L. Kirifides¹, Michael P. Kurnellas¹, Larry Clark² and Bruce P. Bryant^1,*

¹ Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104-3308, USA
² United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, 4101 La Porte Avenue, Fort Collins, CO 80521-2154, USA

View larger version (18K): [in a new window]   Fig. 1. Typical response profile for a cell indicating changes in fluorescence ratio as a function of time and extracellular concentration of stimulus: (A) methyl anthranilate (MA) and (B) capsaicin (CAP). The latency for peak response was 5–10 s after stimulation.

View larger version (13K): [in a new window]   Fig. 2. The proportion of cells responding to criterion condition as a function of stimulus concentration: methyl anthranilate (MA; N=43); capsaicin (CAP; N=55). Positive responses were scored when intracellular calcium concentrations were at least 10% of the level of the terminal stimulation with KCl.

View larger version (16K): [in a new window]   Fig. 3. The mean percent of peak calcium influx (normalized to the response of each neuron to KCl) as a function of the concentration of methyl anthranilate (MA; closed squares) or capsaicin (CAP; open squares). Potassium chloride (40 mmol l–1) was used as a standard depolarizing stimulus. A 5% threshold is indicated by the broken line.

View larger version (21K): [in a new window]   Fig. 4. Trigeminal neurons respond differentially to methyl anthranilate (MA) and capsaicin (CAP). Some neurons responded only to CAP (middle trace), others to MA only (bottom trace) and others to both (top trace). The top trace has been displaced upward 0.05 units for clarity.

View larger version (17K): [in a new window]   Fig. 5. The response of intracellular calcium to methyl anthranilate (MA) in chick trigeminal ganglion neurons is dependent on extracellular calcium. This figure shows typical chick trigeminal neurons responding to (A) 100 mmol l–1 MA and (B) 100 mmol l–1 capsaicin (CAP). When the extracellular calcium is removed, the responses are null. When extracellular calcium is re-introduced the responses return.

View larger version (20K): [in a new window]   Fig. 6. The physiological response of chick trigeminal ganglion neurons to methyl anthranilate (MA) was also dependent on extracellular sodium, but responses to capsaicin (CAP) were not. (A) The response of a neuron that did not respond to MA when extracellular sodium was removed. The response returned when sodium was re-introduced. (B) A capsaicin-induced increase in intracellular Ca2+ even in the absence of extracellular Na+.