TABLE 1.

The Variables and Their Symbols

Pathway	Species	Concentration	Meaning Function
Stimulus	HRS	y1(t)	Stimulus receptor bound with cAMP
	HRSGS	y2(t)	cAMP-Rs complex bound with Gs
	${\text{G}}_{\text{s}}^{\prime }$	y3(t)	Activated Gs protein
	${\text{G}}_{\text{s}}^{\prime }\text{AC}$	y4(t)	Activated adenylate cyclase
	αsGDP	y5(t)	Hydrolyzed ${\text{G}}_{\text{s}}^{\prime }$
Inhibitory	HRi	y6(t)	Inhibitory receptor bound with cAMP
	HRiGi	y7(t)	cAMP-R; complex bound with Gi
	${\text{G}}_{\text{i}}^{\prime }$	y8(t)	Activated Gi protein
	${\text{HR}}_{\text{s}}{\text{G}}_{\text{i}}^{\prime }$	y9(t)	Activated Gi bound with HRS
	αiGDP	y10(t)	Hydrolyzed ${\text{G}}_{\text{i}}^{\prime }$
Generation and secretion	${\text{G}}_{\text{s}}^{\prime }\text{AC}-\text{ATP}$	y11(t)	Activated AC bound with ATP
	cAMPi	y12(t)	Intracellular cAMP
	iPDE-cAMPi	y13(t)	Intracellular iPDE-cAMP complex
	${\text{cAMP}}_o^{*}$	$y_{14}^{*}(t)$	Total amount of secreted cAMP