The present invention is directed to contryphan peptides having 6-12 amino acids, preferably including one or more D-tryptophan or D-leucine residues. The peptides of the present invention are generically termed "contryphans," although the D-leucine containing contryphans are sometimes referred to as leu-contryphans. More specifically, the present invention is directed to contryphan peptides having the general formula Xaa.sub.1 -Cys-Xaa.sub.2 -Xaa.sub.3 -Xaa.sub.4 -Pro-Xaa.sub.5 -Cys (SEQ ID NO:1), wherein Xaa.sub.1, is any amino acid or des-Xaa.sub.1, Xaa.sub.2 is Pro, 4-trans-hydroxyproline or Val, Xaa.sub.3 is D-Trp, L-Trp, D-Leu or L-Leu, preferably D-Trp or D-Leu, Xaa.sub.4 is any amino acid and Xaa.sub.5 is Trp or Tyr. When the peptide contains Xaa.sub.1, it is preferably Gly, Glu, or Lys, most preferably Gly. When Xaa.sub.3 is D- or L-Trp, Xaa.sub.2 is preferably Pro or 4-trans-hydroxyproline. When Xaa.sub.3 is D- or L-Leu, Xaa.sub.2 is preferably Val. The carboxy terminus may contain a carboxyl or an amide, preferably an amide. The present invention is further directed to the specific contryphan peptides and propeptides as described herein. The present invention is also directed to nucleic acids encoding the contryphan peptides and their propeptides as described herein. The contryphans of the present invention are useful as anticonvulsant or neuroprotective agents.