(+)-Sparteine is a natural alkaloid acting as a ganglionic blocking agent. (+)-Sparteine competitively blocks nicotinic ACh receptor in the neurons.
(+)-Sparteine (2 μM) reduces the ACh-induced current caused by activation of nicotinic AChRs in a voltage-independent manner. (+)-Sparteine (5, 10 μM) reduces the amplitude of the excitatory postsynaptic current (EPSC) and the time constant of the EPSC decay[1].
References:
[1]. Voitenko S, et al. Effect of (+)-sparteine on nicotinic acetylcholine receptors in the neurons of rat superior cervical ganglion. Mol Pharmacol. 1991 Aug;40(2):180-5.