UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                  SCHEDULE 13G

                    Under the Securities Exchange Act of 1934

                               (Amendment No. 5)*

                       Synaptic Pharmaceutical Corporation
--------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                    87156R109
                       -----------------------------------
                                 (CUSIP Number)

                                December 31, 2002
              ------------------------------------------------------
             (Date of Event Which Requires Filing of this Statement)

            Check the appropriate box to designate the rule pursuant
                        to which this Schedule is filed:

                                [x] Rule 13d-1(b)
                                [ ] Rule 13d-1(c)
                                [ ] Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter the
disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).

                               Page 1 of 10 Pages

SEC 1745 (2/92)



CUSIP No. 87156R109              13G                          Page 2 of 10 Pages

--------------------------------------------------------------------------------
 1       NAME OF REPORTING PERSON
         S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

                  Liberty Wanger Asset Management, L.P.  36-3820584

--------------------------------------------------------------------------------
 2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

                  Not Applicable                                         (a)[ ]

                                                                         (b)[ ]

--------------------------------------------------------------------------------
 3       SEC USE ONLY

--------------------------------------------------------------------------------
 4       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

--------------------------------------------------------------------------------
    NUMBER OF     5        SOLE VOTING POWER

     SHARES                         None

  BENEFICIALLY    --------------------------------------------------------------
                  6        SHARED VOTING POWER
    OWNED BY
                                    917,000
      EACH
                  --------------------------------------------------------------
   REPORTING      7        SOLE DISPOSITIVE POWER

  PERSON WITH                       None

                  --------------------------------------------------------------
                  8        SHARED DISPOSITIVE POWER

                                    917,000

--------------------------------------------------------------------------------
 9       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  917,000

--------------------------------------------------------------------------------
10       CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

                  Not Applicable                                            [ ]

--------------------------------------------------------------------------------
11       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

                  8.4%

--------------------------------------------------------------------------------
12       TYPE OF REPORTING PERSON*

                  IA

--------------------------------------------------------------------------------



CUSIP No. 87156R109               13G                         Page 3 of 10 Pages

--------------------------------------------------------------------------------
 1       NAME OF REPORTING PERSON
         S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

                  WAM Acquisition GP, Inc.

--------------------------------------------------------------------------------
 2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

                  Not Applicable                                         (a)[ ]

                                                                         (b)[ ]

--------------------------------------------------------------------------------
 3       SEC USE ONLY

--------------------------------------------------------------------------------
 4       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Delaware

--------------------------------------------------------------------------------
    NUMBER OF     5        SOLE VOTING POWER

     SHARES                         None
                  --------------------------------------------------------------
  BENEFICIALLY    6        SHARED VOTING POWER

    OWNED BY                        917,000
                  --------------------------------------------------------------
      EACH        7        SOLE DISPOSITIVE POWER

   REPORTING                        None
                  --------------------------------------------------------------
  PERSON WITH     8        SHARED DISPOSITIVE POWER

                                    917,000

--------------------------------------------------------------------------------
 9       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  917,000

--------------------------------------------------------------------------------
10       CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

                  Not Applicable                                            [ ]

--------------------------------------------------------------------------------
11       PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

                  8.4%

--------------------------------------------------------------------------------
12       TYPE OF REPORTING PERSON*

                  CO

--------------------------------------------------------------------------------



CUSIP No. 87156R109                     13G                   Page 4 of 10 Pages

--------------------------------------------------------------------------------
 1       NAME OF REPORTING PERSON
         S.S. or I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

                  Liberty Acorn Trust

--------------------------------------------------------------------------------
 2       CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*

                  Not Applicable                                         (a)[ ]
                                                                         (b)[ ]
--------------------------------------------------------------------------------
 3       SEC USE ONLY

--------------------------------------------------------------------------------
 4       CITIZENSHIP OR PLACE OF ORGANIZATION

                  Massachusetts

--------------------------------------------------------------------------------
    NUMBER OF     5        SOLE VOTING POWER

     SHARES                         None

  BENEFICIALLY    --------------------------------------------------------------
                  6        SHARED VOTING POWER
    OWNED BY
                                    917,000
      EACH
                  --------------------------------------------------------------
   REPORTING      7        SOLE DISPOSITIVE POWER

  PERSON WITH                       None

                  --------------------------------------------------------------
                  8        SHARED DISPOSITIVE POWER

                                    917,000

--------------------------------------------------------------------------------
 9       AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                  917,000

--------------------------------------------------------------------------------
10   CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES*

                  Not Applicable                                            [ ]

--------------------------------------------------------------------------------
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

                  8.4%

--------------------------------------------------------------------------------
12   TYPE OF REPORTING PERSON*

                  IV

--------------------------------------------------------------------------------



Item 1(a)                  Name of Issuer:

                                    Synaptic Pharmaceutical Corporation

Item 1(b)                  Address of Issuer's Principal Executive Offices:

                                    215 College Road
                                    Paramus, NJ 07652

Item 2(a)                  Name of Person Filing:

                                    Liberty Wanger Asset Management, L.P.
                                     ("WAM")
                                    WAM Acquisition GP, Inc., the general
                                     partner of WAM ("WAM GP")
                                    Liberty Acorn Trust ("Acorn")

Item 2(b)                  Address of Principal Business Office:

                                    WAM, WAM GP and Acorn are all located at:

                                    227 West Monroe Street, Suite 3000
                                    Chicago, Illinois  60606

Item 2(c)                  Citizenship:

                                    WAM is a Delaware limited partnership; WAM
                                    GP is a Delaware corporation; and Acorn is a
                                    Massachusetts business trust.

Item 2(d)                  Title of Class of Securities:

                                    Common Stock

Item 2(e)                  CUSIP Number:

                                    87156R109

Item 3                     Type of Person:

                                    (d)     Acorn is an Investment Company under
                                            section 8 of the Investment Company
                                            Act.

                                    (e)     WAM is an Investment Adviser
                                            registered under section 203 of the
                                            Investment Advisers Act of 1940; WAM
                                            GP is the General Partner of the
                                            Investment Adviser.

                               Page 5 of 10 Pages



Item 4                     Ownership (at December 31, 2002):

                                    (a)     Amount owned "beneficially" within
                                            the meaning of rule 13d-3:

                                            917,000

                                    (b)     Percent of class:

                                            8.4% (based on 10,977,790 shares
                                            outstanding as of November 1, 2002).

                                    (c)     Number of shares as to which such
                                            person has:

                                                 (i)  sole power to vote or to
                                                      direct the vote:  none

                                                (ii)  shared power to vote or
                                                      to direct the vote:
                                                      917,000

                                               (iii)  sole power to dispose or
                                                      to direct the
                                                      disposition of:  none

                                                (iv)  shared power to dispose
                                                      or to direct disposition
                                                      of:  917,000

Item 5                     Ownership of Five Percent or Less of a Class:

                                    Not Applicable

Item 6                     Ownership of More than Five Percent on Behalf of
                           Another Person:

                                    The shares reported herein have been
                                    acquired on behalf of discretionary clients
                                    of WAM, including Acorn. Persons other than
                                    WAM and WAM GP are entitled to receive all
                                    dividends from, and proceeds from the sale
                                    of, those shares. Acorn is the only such
                                    person known to be entitled to all dividends
                                    from, and all proceeds from the sale of,
                                    shares reported herein to the extent of more
                                    than 5% of the class.

Item 7                     Identification and Classification of the Subsidiary
                           Which Acquired the Security Being Reported on by the
                           Parent Holding Company:

                                    Not Applicable

Item 8                     Identification and Classification of Members of the
                           Group:

                                    Not Applicable

Item 9                     Notice of Dissolution of Group:

                                    Not Applicable

                               Page 6 of 10 Pages



Item 10                    Certification:

                                    By signing below I certify that, to the best
                           of my knowledge and belief, the securities referred
                           to above were acquired and are held in the ordinary
                           course of business and were not acquired and are not
                           held for the purpose of or with the effect of
                           changing or influencing the control of the issuer of
                           the securities and were not acquired and are not held
                           in connection with or as a participant in any
                           transaction having that purpose or effect.

                               Page 7 of 10 Pages



                                       Signature

         After reasonable inquiry and to the best of my knowledge and belief, I
certify that the information set forth in this statement is true, complete and
correct.

Date:  February 4, 2003

                           The undersigned corporation, on the date above
                           written, agrees and consents to the joint filing on
                           its behalf of this Schedule 13G in connection with
                           its beneficial ownership of the security reported
                           herein.

                                    WAM Acquisition GP, Inc.
                                     for itself and as general partner of
                                     LIBERTY WANGER ASSET MANAGEMENT, L.P.

                                    By: /s/ Bruce H. Lauer
                                        ----------------------------------------
                                            Bruce H. Lauer
                                            Senior Vice President and Secretary

                           The undersigned corporation, on the date above
                           written, agrees and consents to the joint filing on
                           its behalf of this Schedule 13G in connection with
                           its beneficial ownership of the security reported
                           herein.

                                    LIBERTY ACORN TRUST

                                    By: /s/ Bruce H. Lauer
                                        ----------------------------------------
                                            Bruce H. Lauer
                                            Vice President, Treasurer and
                                            Secretary

                               Page 8 of 10 Pages



                                            Exhibit Index

Exhibit 1         Joint Filing Agreement dated as of February 4, 2003 by and
                  among Liberty Wanger Asset Management, L.P., WAM Acquisition
                  GP, Inc. and Liberty Acorn Trust

                               Page 9 of 10 Pages