Odor discrimination of "IP3-" and "cAMP-increasing" odorants in the turtle olfactory bulb

Long-term recording of olfactory and vomeronasal stimulant-induced waves from the turtle main olfactory bulb and accessory olfactory bulb

Recording of stimulant-induced waves (bulbar responses) from the main olfactory bulb is a useful tool for measuring quantitative stable olfactory responses. There is a good relationship between the olfactory bulbar response, olfactory nerve response and electroolfactogram (EOG), suggesting that the bulbar response reflects events in receptor cells. The modern whole-cell recording technique offers direct information on olfactory transduction in single cells, but it requires long experimental periods and many animals. On the other hand, analysis of bulbar responses provides useful information and requires the use of few animals. For example, we found that cAMP-increasing and IP3-increasing odorants were not distinctly received by the turtle olfactory organ by measuring olfactory bulbar responses and analyzed with a multidimensional scaling from about 60 animals. However, to record similar odor responses from isolated turtle olfactory neurons, at least 200 animals would be necessary. Bulbar responses are recorded with electrodes implanted into or located on the main olfactory bulb. When electrodes are located on the olfactory bulb surface, it is possible to record stable responses over a period of 3 days. These methods were applied successfully to the accessory olfactory bulb. In this paper, we describe the protocols used for recording of the stimulant-induced waves from the main and accessory olfactory bulb.

Odor discrimination of 'cAMP-' and 'IP3-increasing' odorants at high temperature and at high NaCl concentration in turtle olfactory system

The ability of the turtle olfactory system to discriminate between various cAMP- and IP3-increasing odorants at high temperature and at high NaCl concentration in the olfactory bulb was examined by the cross-adaptation technique. The degrees of discrimination in high [Na+] solution were similar to those in normal Ringer's solution, suggesting that selectivities of receptors coupled with cAMP- and IP3-dependent pathways are similar to those coupled with both cAMP- and IP3-independent pathways. The mean values of the degree of discrimination among the IP3-increasing odorants were higher than those among the cAMP-increasing odorants at high temperature and at high [Na+] concentration. The degrees of discrimination among the IP3-increasing odorants at 40 degrees C were greater than those at 25 degrees C, while those among the cAMP-increasing odorants at 40 degrees C were similar to those at 25 degrees C, suggesting that the features of the receptors of cAMP-increasing odorants are different from those which respond to IP3-increasing odorants.