Since you now know a little bit about dose-response relationships you are ready for my summary of the next planarian pharmacology paper, coming soon!
A cembranoid from tobacco prevents the expression of nicotine-induced withdrawal behavior in planarian worms.
Pagán OR, Rowlands AL, Fattore AL, Coudron T, Urban KR, Bidja AH, Eterović VA. Eur J Pharmacol. 2009 Aug 1;615(1-3):118-24. doi: 10.1016/j.ejphar.2009.05.022. Epub 2009 May 30.