Table 1.

Effect of L-citrulline on the release of [³H]ACh, adenine nucleotides (ATP) and adenosine (ADO) from stimulated motor nerve terminals in the absence and in the presence of the nucleoside transport inhibitor, NBTI (10 μM)

	S2/S1 ratios
	[3H]ACh release	ATP release	ADO release
Control	0.81±0.03 (8)	0.95±0.02 (4)	0.86±0.05 (4)
L-Citrulline (470 μM)	0.59±0.03 (6)*	0.66±0.05 (4)*	0.91±0.12 (4)
L-Citrulline (470 μM)+NBTI (10 μM)	0.80±0.06 (5)	0.95±0.09 (4)	0.76±0.03 (4)

The release of [³H]ACh, ATP and ADO was elicited by two trains (S₁ and S₂) of electrical stimulation consisting of 750 pulses delivered at a 5 Hz frequency (0.04 ms pulse duration). Values for S₂/S₁ ratios are means±s.e.m. L-Citrulline (470 μM) was applied 15 min before S₂. NBTI (10 μM) was present throughout the assay, including S₁ and S₂; the S₂/S₁ ratio obtained in the presence of NBTI (10 μM) alone was not statistically different from control ratios (without any drug during S₁ and S₂). The number of experiments is given in parentheses.

^*P<0.05 (one-way ANOVA followed by Dunnett's modified t-test), significant differences from the control.