. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 172 R K. ZIMMER-FAUST ET ATP ADP AMP ADO B c o Q. in Q. 30 20 ATP AMPPNP P. interruptus ATP AMPPNP P. argus Figure 5. A. Relative activities of adenine nuclcotides and adcno- sine on ATP-sensitive cells of two lobster species. Each compound was presented at a concentration of 100 nM Bars represent mean responses ± SEM for 11 cells in Panulinis intemipnts and at least 6 cells in P. arvu\ B Relative activity of 10 n\t ATP and 10 nM {J,7-imidoATP (AMPPNP) on ATP-scnsitive cells. Bars are mean values ± SEM for four cells in
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 172 R K. ZIMMER-FAUST ET ATP ADP AMP ADO B c o Q. in Q. 30 20 ATP AMPPNP P. interruptus ATP AMPPNP P. argus Figure 5. A. Relative activities of adenine nuclcotides and adcno- sine on ATP-sensitive cells of two lobster species. Each compound was presented at a concentration of 100 nM Bars represent mean responses ± SEM for 11 cells in Panulinis intemipnts and at least 6 cells in P. arvu\ B Relative activity of 10 n\t ATP and 10 nM {J,7-imidoATP (AMPPNP) on ATP-scnsitive cells. Bars are mean values ± SEM for four cells in P. interruptus and six cells in P. argiis. Data for P. argus taken from Carr el al. (1986). cells; , see responses of taurine-best cells (Fuzessery et 1978) and AMP-best cells (Derby et al., 1984). Since Pi-type purinoceptors are also rapidly desensitized by ATP and related analogs (Burnstock and Kennedy. 1985). it would appear that the ATP-sensitive chemore- ceptors exhibit yet another property characteristic of P: receptors. An important discrepancy in the behavioral and phys- iological data for P. interruptus is that the behavioral sen- sitivity to ATP is approximately 30-fold greater than that determined physiologically for the ATP-sensitive cells (compare D-R curves for ATP in Figs. 3 and 4B). If our physiological and behavioral sensitivity measurements are both accurate, this discrepancy would appear to be inconsistent with the hypothesis that these cells mediate the ATP-stimulatcd locomotory response; , suggest- ing that an as yet unidentified population of chemore- ceptors with a lower threshold for ATP is responsible for inducing the behavior. However, another possible expla- nation for the difference could be that convergence of peripheral neurons in the CNS (van Drongelen et al., 1978) plays a role in enhancing the behavioral sensitivity to ATP. Indeed, in several insect species, convergence of many pheromone receptor cells onto fewer neurons in the C
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