three hypotheses accounting for the localization of acetylcholinesterase within and/or on substantia nigra , pars compacta neurons are presented and evaluated : ( a ) to catabolize acetylcholine released from afferent cholinergic fibers , ( b ) to catabolize substance p released from some neostriato-nigral axon terminals , and/or ( c ) to serve as a communication link with nigral vasculature .
C0038590
substantia nigra
C0175412
pars compacta