Question: How do I plot a series of differential equations with undefined constants?

I am trying to plot four different DEs on one graph, but Maple does not like the fact that I have several constants that are not assigned to numerical values.  Here is my code:

> with(DEtools);

> de1 := diff(q1(t), t) = dose*Dirac(t)-k12*q1(t);

                     d                                  
                    --- q1(t) = dose Dirac(t) - k12 q1(t)
                     dt                                 
> de2 := diff(q2(t), t) = k12*q1(t)+k32*q3(t)-k23*q2(t)-k24*q2(t);

           d                                                      
          --- q2(t) = k12 q1(t) + k32 q3(t) - k23 q2(t) - k24 q2(t)
           dt                                                     
> de3 := diff(q3(t), t) = k23*q2(t)-k32*q3(t);

                       d                              
                      --- q3(t) = k23 q2(t) - k32 q3(t)
                       dt                             
> de4 := diff(q4(t), t) = k24*q2(t)-kel*q4(t);

                       d                              
                      --- q4(t) = k24 q2(t) - kel q4(t)
                       dt                             
> assume(k12, integer);
%;
> DEplot([de1], [q1(t)], t = 0 .. 10, [q1(0) = dose]);
%;
Error, (in DEtools/DEplot/CheckDE) extra unknowns found: dose

Please help!