Fig. 1
Analytical description of an IEG expression in response to plasticity related events. a A simple consecutive reaction kinetics for the mRNA (A), protein (B) and degraded protein (C) describes the response to a plasticity signal. The reaction is assumed to proceed with first order forward reaction rate constants kf and kd for the synthesis and degradation of proteins, respectively. b Solving the coupled differential equations of the sequential chemical reaction described in (a), we get an expression (Eq. 1) for F1(t) that describes the fluorescence intensity corresponding to IEG coupled fluorophore at any given time ‘t’ as a difference of two exponential terms with rate constants, kf and kd. The lines are the simulated response functions for five values of kf/kd ratios with parameter A and kf set to 1D.U and 0.1 min−1. Time to maximal response, one of the key parameters necessary to time the neuronal tagging is plotted for these set of ratios as a scatter plot in the inset. The colour of the open circles corresponds to their respective solid lines. The red dashed line is a straight line fit of these scatter plot. c Similarly, we describe Eq. 2 for a neuron that got activated twice where A, kf, kd are as previously described and td is the time of second activation event. Equation 2 is simulated (solid lines) to show the response for four ratios of kf/kd with parameter A set to 1D.U., and the time gap between the two events (td) is set to 60 min as indicated by the black dotted line