Generating a (relatively) large current from a small battery at 2 Hz?
So, after a bit back and forth, let's compile your requirements:


Constant current source 1.5mA
Maximum equiv. load resistance 100kOhm
50% duty cycle at 2 Hz
Battery powered


So, we can directly infer a few things:


You'll need some kind of DC/DC converter to convert your battery voltage (&lt;20V) to the voltage you'll need to push 1.5mA through 100kOhm; namely, an step-up converter to 150V
The power consumption of your load in on-state. is U·I = 1.5e2V·1.5e-3 A = 2.25e-1W = 0.225 W. With the 50 % duty cycle, that means your battery needs to supply an average of 112.5 mW – that's far more than a coin cell will do for more than a couple of seconds. 


Normally, with modest output currents and at less extreme input/output voltage rations, step-up supply problems are often solved with inverting switch-mode power supplies, or simple boost topologies. However, nothing changes the fact that you'll need a flyback converter, here.

There's ICs that offer that functionality (flyback converters). For example, the TI LM2858 "simpleSwitcher" module. 

Now you have a choice:


Generate >150V and use a constant current sink (e.g. transistor pair in a "current mirror" configuration) drop exactly as much voltage as necessary to keep the current at a constant 1.5 mA
Modify the schematic of the step-up converter, which is normally a voltage-feedback design, to be a current-feedback design


Since we're battery-based, the latter seems the best choice.

The 2Hz on/off switching is probably best done with a simple microcontroller, or something boring like a NE555 (watch the power consumption of the latter option). 

Still note that you need to supply an average of 112.5W – a single AA-battery supplies 1.5V and has a capacity of about 2.8 Ah (according to German wikipedia), so it has a capacity of 4.2 Wh, and the four you'd need to get to 6V would have a total capacity of 16.8 Wh. With that, your circuit, at a very generously estimated step-up conversion efficiency of 70% would run a best-case of ca 11.5 Wh/0.1125 W ~= 100h off that.  

Note that designing such a step-up converter isn't trivial – flybacks need custom-wound transformers, and at 150V, you want to make sure you don't electrocute yourself.