The following are true about the muscarinic receptors:
a. they are found at the postganglionic parasympathetic synapses
b. they can be selectively blocked by atropine
c. M1 muscarinic receptors are found in the brain
d. all above
a. they are found at the postganglionic parasympathetic synapses
b. they can be selectively blocked by atropine
c. M1 muscarinic receptors are found in the brain
d. all above