What is "get the dope on"

Dope \Dope\ (d[=o]p), n. [D. doop a dipping, fr. doopen to dip. Cf. Dip.]

1. Any thick liquid or pasty preparation, as of opium for medicinal purposes, of grease for a lubricant, etc.

2. Any preparation, as of opium, used to stupefy or, in the case of a race horse, to stimulate. [Slang or Cant]

3. An absorbent material; esp., in high explosives, the sawdust, infusorial earth, mica, etc., mixed with nitroglycerin to make a damp powder (dynamite, etc.) less dangerous to transport, and ordinarily explosive only by suitable fulminating caps.

4. Information concerning the previous performances of race horses, or other facts concerning them which may be of assistance in judging of their chances of winning future races; similar information concerning other sports; by extension, any information not generally known, especially when coming from an inside source; as, the inside dope.

5. an ignorant or stupid person. [Colloq.]

   get the dope on learn the true story; get the inside information.