Table 2.

Inhibition of the cardiopulmonary chemoreflex responses, PBG (1–8 µg/kg), after microinjections of selective A_2a agonist (CGS-21680) or A_2a antagonist (ZM-241385).

DRUGS	PBG µg/kg	MAP Δ%	HR Δ bpm	RSNA Δ%	pre-ASNA Δ%	LSNA Δ%
CGS-21680 0.2 pmol/ 50 nl	1	36.8 ± 13.5	−33.8 ± 28.2	−4.4 ± 37.4	26.4 ± 18.2	−1.3 ± 26.9
	2	26.0 ± 12.8	−10.9 ± 16.8	27.4 ± 10.3	−1.3 ± 22.9	10.4 ± 10.4
	4	16.6 ± 6.8	−18.9 ± 22.0	12.8 ± 5.5	5.4 ± 9.7	14.2 ± 7.2
	8	9.0 ± 8.2	5.6 ± 10.3	2.3 ± 3.0	1.5 ± 5.7	3.0 ± 4.2
ZM-241385 40 pmol/ 100 nl	1	−23.8 ± 36.1	−43.9 ± 30.2	5.6 ± 14.3	16.7 ± 10.0	9.9 ± 20.3
	2	−2.7 ± 18.3	−53.2 ± 26.3	−9.9 ± 10.2	−36.6 ± 26.0	−5.0 ± 12.0
	4	14.0 ± 6.0	−25.1 ± 23.1	1.4 ± 2.6	1.0 ± 5.5	8.7 ± 3.1
	8	13.0 ± 3.8	23.1 ± 10.4	1.9 ± 1.6	2.6 ± 4.6	3.8 ± 4.4

Data are expressed as percent inhibition from control responses which are standardized to zero level. Positive values represent inhibition of the reflex while negative numbers suggest facilitation of the responses. Values are means ± SE. PBG, phenylbiguanide; MAP, mean arterial pressure; HR, heart rate; RSNA, renal sympathetic nerve activity; pre-ASNA, preganglionic adrenal sympathetic nerve activity; LSNA, lumbar sympathetic nerve activity. Two-way ANOVA showed a significant drug effect (P=0.022) at moderate activation of the reflex (PBG, 2 µg/kg) but no differences across the nerves (P>0.05 for all doses of PBG).