Fig. 1.

Response of wild-type and mutant preparations to nerve stimulation and α-Ltx at permissive and nonpermissive temperatures. A, Nerve impulse-evoked ejps in the standard recording solution in wild-type (WT) andcsp (CSP) and shibire(Shi) mutant preparations at permissive (21°C) and after 15 min at nonpermissive (32°C) temperature. To obtain this ts blockade of ejps in shibire mutants it was necessary to pretreat the preparation in high-K solution until mejps ceased at 32°C. This was done by warming the preparation to 32°C and incubating it for 15 min in high-K solution (see Materials and Methods), followed by washing with normal recording solution. No such treatment was needed for csp mutants, which were fully blocked after 10–15 min at 32°C. Shibire andcsp mutants recover ejps after 15 min at 21°C.B, Effect of α-Ltx on mejp discharges in wild-type,csp, and shibire mutant preparations at permissive (21°C) and nonpermissive temperatures (32°C). Toxin (5 nm) was added at time 0, and representative mejp traces are presented at selected intervals thereafter. Note that prolonged exposure of wild-type larvae to 32°C often results in spontaneous ejps seen as spikes in the bottom traces. This spiking is not seen in csp or depleted shibirepreparations. Again, as in A, the shibiremutant preparation was depleted of releasable quanta at 32°C by exposure to high-K solution. Note that a similar pretreatment of control or csp mutant preparations with high-K solution did not alter the α-Ltx effect (data not shown). Data are representative of results from a minimum of three experiments for each condition.