Table 3.

Variables of response-intensity relationships determined from STX-sensitive (STX-S) and STX-resistant (STX-R) nerves isolated from farmed oysters fed with A. minutum (toxic-alga-exposed oysters) or with T. lutea (control oysters), before (untreated) and after pre-treatment of nerves with 8.39 μM STX.

	I50 (μA)				S (μA−1)
	Untreated STX-S	Pre-Treated STX-S	Untreated STX-R	Pre-Treated STX-R	Untreated STX-S	Pre-treated STX-S	Untreated STX-R	Pre-Treated STX-R
Control oysters (n = 8–10 nerves)	33.16 ± 0.95	33.47 ± 1.06	34.18 ± 0.51	34.59 ± 0.62	10.10 ± 0.59	9.09 ± 0.24	10.77 ± 0.33	10.81 ± 0.28
Toxic-alga-exposed oysters (n = 6–12 nerves)	33.97 ± 0.74	34.10 ± 0.82	32.12 ± 3.81	34.06 ± 0.97	10.82 ± 0.23	10.58 ± 0.18	10.04 ± 2.10	10.70 ± 0.27

I₅₀, stimulus intensity producing a CNAP with 50% maximal peak amplitude; and S, slope of the curve.