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4. Catechol enzyme that adds a methyl to finish NA off (4 letters)
8. Small talk? No: it builds ACh from acetyl CoA and choline (4 letters)
10. The cleft's cleanup crew that never clocks out, chopping ACh in two (20 letters)
12. 1970 Nobel for showing ACh is released in packets (4 letters)
13. Tobacco-named ACh receptor that is itself the ion channel (9 letters)
20. Beta protein that binds a GRK-tagged receptor and silences it (8 letters)
23. Mitochondrial enzyme that oxidizes amines; block it and skip the aged cheese (3 letters)
24. Dreamed up the frog heart experiment proving the vagus talks with a chemical (5 letters)
25. Rest and digest: long pre, short post, muscarinic at the target (15 letters)

1. Equation for the voltage where one ion stops moving net (6 letters)
2. Slowest step on the catecholamine line: tyrosine gets an OH (11 letters)
3. What dopamine becomes after beta-hydroxylase; the sympathetic target's messenger (13 letters)
5. Mushroom-named GPCR for ACh; M2 and M4 put on the brakes (10 letters)
6. Swaps protons to stuff ACh into its vesicle (5 letters)
7. Tether, dock, fuse: the zipper crew for vesicle release (5 letters)
9. Takes the CO2 off L-DOPA to make dopamine (13 letters)
11. Cheese-board amine that turns dangerous with an MAO inhibitor (8 letters)
14. Arrow-tip alkaloid that blocks nicotinic receptors at the neuromuscular junction (12 letters)
15. The adrenal medulla's methyl-adder that makes adrenaline (4 letters)
16. Named ACh's receptors after a mushroom and tobacco (7 letters)
17. Six-carbon blocker that shuts nicotinic receptors at both autonomic ganglia (13 letters)
18. The vesicle's half of the SNARE zipper, a femme fatale of a name (4 letters)
19. Asked why the adrenaline response fades while adrenaline is still there (9 letters)
21. Gaps in the myelin where the signal gets recharged (7 letters)
22. Half of ACh's remains, hauled home by a sodium-powered carrier (7 letters)