Figure 1. Time course and quantification of the CtVm-induced elevation of somatic [Ca²⁺]_i in bag cell neurones in nASW.

A, time course of a CtVm-induced increase in somatic [Ca²⁺]_i for a bag cell neurone in nASW possessing both peak-type and gradual changes to steady-state levels. Seven minutes after application of 100 μg ml⁻¹ CtVm, there was a rapid and marked increase in [Ca²⁺]_i from a control level of ∼250 nM to a peak of ∼450 nM. The [Ca²⁺]_i subsequently plateaued at a steady-state level of ∼350 nM, and upon wash in nASW, returned to a near-control level of ∼275 nM. B, time course of a CtVm-induced increase in somatic [Ca²⁺]_i displaying only a slow change in steady-state levels and lacking a peak-type response. Four minutes after application of CtVm, a gradual increase in [Ca²⁺]_i developed from a baseline of ∼240 nM to a steady-state level of ∼360 nM. Following wash in nASW, the [Ca²⁺]_i returned to a level of ∼275 nM. C, grouped data of 16 CtVm responses in nASW reveals that the somatic [Ca²⁺]_i during both the peak (when it occurred) and the steady-state periods were significantly greater than that of control (P < 0.0001, paired t test in both cases). The t test is used instead of an ANOVA because the peak-type response occurred only in 9 of the 16 cells that were initially tested. D, the response to CtVm in the presence of 100 μM TTX. On its own, TTX had no effect on [Ca²⁺]_i, furthermore, CtVm was still effective in elevating [Ca²⁺]_i from a baseline of ∼250 nM to a steady-state level of ∼475 nM, which recovered following wash out of CtVm. The CtVm-induced [Ca²⁺]_i increase in TTX lacked a peak-type response and was typically slower in onset as compared with the CtVm response in nASW alone.