Exhibit 4.2 ----------- FIRST AMENDMENT TO RIGHTS AGREEMENT FIRST AMENDMENT, dated October 19, 2001 (this "Amendment"), between Synaptic Pharmaceutical Corporation, a Delaware corporation (the "Company") and Mellon Investor Services LLC, a New Jersey...Rights Agreement • February 13th, 2002 • Synaptic Pharmaceutical Corp • Biological products, (no disgnostic substances) • Delaware
