  In this letter, we investigate the mutual information rate (MIR) achieved by
an independent identically distributed (IID) Gaussian input on the
intensity-driven signal transduction channel. Specifically, the asymptotic
expression of the continuous-time MIR is given. Next, aiming at low
computational complexity, we also deduce an approximately numerical solution
for this MIR. Moreover, the corresponding lower and upper bounds that can be
used to find the capacity-achieving input distribution parameters are derived
in closed-form. Finally, simulation results show the accuracy of our analysis.
