. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 1 atm 272 atm Pressure Figure 8. The effects of hydrostatic pressure on Anlimora mslrata basal adenylyl cydase activity (open bar) and inhibition of basal ade- nylyl cyclase activity by the adenosine analogs CPA (100 //A/; filled bar) and NECA (100 hatched bar). Membranes were incubated at atmosphenc pressure or 212 atm pressure for 2 h at 5°C. All values are standardized to the I atm basal adenylyl cyclase activity. The 1 atm and 272 atm basal activities were pmol mm ' mg protein''. The 1 atm data are the m
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 1 atm 272 atm Pressure Figure 8. The effects of hydrostatic pressure on Anlimora mslrata basal adenylyl cydase activity (open bar) and inhibition of basal ade- nylyl cyclase activity by the adenosine analogs CPA (100 //A/; filled bar) and NECA (100 hatched bar). Membranes were incubated at atmosphenc pressure or 212 atm pressure for 2 h at 5°C. All values are standardized to the I atm basal adenylyl cyclase activity. The 1 atm and 272 atm basal activities were pmol mm ' mg protein''. The 1 atm data are the mean of three replicates: the 272 atm values are the mean of six replicates. The average standard errors are 1 of the values of the mean. Discussion Binding of the agonist [3H]CHA to the A, receptor in A. rostrata brain membranes at 5°C is saturable and readily reversible (Figs. 1. 2. 3). At 5°C, the rate constants determined for A. rostrata from association-dissociation experiments are lower than those reported for two scor- paenid fishes, Sebastolobus alascanus and 5. altivelis, at a measurement temperature of 22°C (Murray and Siebe- naller, 1987). The kobsfortheA rostrata binding reaction is only 21 to 25% of the values obtained for the Sebasto- lobus species ai 22°C. Thek_! value for A. rostrata is only 40 to 65% of the 22°C values. At 22°C the binding reac- tion in Sebastolobus membranes is complete in 30 min. In contrast, at 5°C, the reaction in A. rostrata mem- branes takes more than four times as long to reach equi- librium (Fig. 1). At 5°C, which approximates the body temperatures of these three species, the K^ values are similar (Siebenaller and Murray, 1988). At 5°C, the rank order potencies of agonists is compat- ible with that expected for the A, receptor (Fig. 9; Siebe- naller and Murray, 1988). The K, values indicate dis- crimination of the R- and S-diastereomers of PIA ( and nM, respectively). The rank order potency se- ries expected for A
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