<PAGE>
 
                                   EXHIBIT A

                                                               Warrant No. A-
                                                                             ---
                    CLASS A WARRANT TO PURCHASE A MAXIMUM OF
                                SHARES OF COMMON STOCK OF
                      ---------
                       NEUROBIOLOGICAL TECHNOLOGIES, INC.

                          (Void after _____, 1999)

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED.  THEY MAY NOT BE SOLD, OFFERED FOR SALE, PLEDGED OR HYPOTHECATED IN THE
ABSENCE OF A REGISTRATION STATEMENT IN EFFECT WITH RESPECT TO THE SECURITIES
UNDER SUCH ACT OR AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY THAT SUCH
REGISTRATION IS NOT REQUIRED OR UNLESS SOLD PURSUANT TO RULE 144 OF SUCH ACT.

THIS WARRANT AND THE SHARES PURCHASABLE HEREUNDER ARE SUBJECT TO RESTRICTIONS ON
TRANSFER AS SET FORTH HEREIN.

          This certifies that               (the "Holder"), or assigns, for
                              -------------
value received, is entitled to purchase from Neurobiological Technologies, Inc.,
a Delaware corporation (the "Company"), subject to the terms set forth below, a
maximum of            (the "Warrant Shares") fully paid and nonassessable shares
           ----------
(subject to adjustment as provided herein) of the Company's Common Stock, $.001
par value (the "Common Stock"),for cash at a price of $.75 per share (the
"Exercise Price") (subject to adjustment as provided herein) at any time or from
time to time up to and including 5:00 p.m. (California Time) on               ,
                                                                          ----
1999, (the "Expiration Date") upon surrender to the Company at its principal
office (or at such other location as the Company may advise the Holder in
writing) of this Warrant properly endorsed with the Form of Subscription
attached hereto duly filled in and signed and upon payment in cash or by check
of the aggregate Exercise Price for the number of shares for which this Warrant
is being exercised determined in accordance with the provisions hereof.  The
Exercise Price is subject to adjustment as provided in Section 3 of this
Warrant.  This Warrant is issued subject to the following terms and conditions:
<PAGE>
 
          1.  EXERCISE, ISSUANCE OF CERTIFICATES, REDUCTION IN NUMBER OF WARRANT
SHARES.

          1.1  GENERAL.  This Warrant is exercisable at the option of the Holder
of record hereof on or prior to the Expiration Date, at any time or from time to
time following its issuance, for all or any part of the Warrant Shares (but not
for a fraction of a share) which may be purchased hereunder, as that number may
be adjusted pursuant to Section 3 of this Warrant.  The Company agrees that the
Warrant Shares purchased under this Warrant shall be and are deemed to be issued
to the Holder hereof as the record owner of such Warrant Shares as of the close
of business on the date on which this Warrant shall have been surrendered,
properly endorsed, the completed and executed Form of Subscription delivered,
and payment made for such Warrant Shares.  Certificates for the Warrant Shares
so purchased, together with any other securities or property to which the Holder
hereof is entitled upon such exercise, shall be delivered to the Holder hereof
by the Company at the Company's expense not later than 10 days after the rights
represented by this Warrant have been so exercised.  In case of a purchase of
less than all the Warrant Shares which may be purchased under this Warrant, the
Company shall cancel this Warrant and execute and deliver to the Holder hereof
within a reasonable time a new Warrant or Warrants of like tenor for the balance
of the Warrant Shares purchasable under the Warrant surrendered upon such
purchase.  Each stock certificate so delivered shall be registered in the name
of such Holder.

          1.2  NET ISSUE EXERCISE OF WARRANT.  Notwithstanding any provisions
herein to the contrary, if the fair market value of one share of Common Stock is
greater than the Exercise Price (at the date of calculation as set forth below),
in lieu of exercising this Warrant for cash, Holder may elect to receive shares
of Common Stock equal to the value (as determined below) of this Warrant (or the
portion thereof being canceled) by surrender of this Warrant at the principal
office of the Company together with the properly endorsed Form of Subscription
in which event the Company shall issue to the Holder a number of shares of
Common Stock computed using the following formula:

          X=  Y (A-B)
              -------
                 A

Where     X=  the number of shares of Common Stock to be issued to Holder;

          Y=  the number of shares of Common Stock purchasable under the Warrant
              or, if only a portion of the Warrant is being exercised, the
              portion of the Warrant being canceled (at the date of such
              calculation);

                                       2
<PAGE>
 
          A=  the fair market value of one share of the Company's Common Stock
              (at the date of such calculation); and

          B=  Exercise Price (as adjusted to the date of such calculation).

For purposes of the above calculation, the fair market value of one share of
Common Stock shall be the average of the closing bid and asked prices of the
Common Stock quoted in the over-the-counter market summary or the last reported
sale price of the Common Stock or the closing price quoted on the Nasdaq
National Market System or on any exchange on which the Common Stock is listed,
whichever is applicable, as published in The Wall Street Journal for the five
trading days prior to the date of determination of fair market value.

     2.   SHARES TO BE FULLY PAID.  The Company covenants and agrees that all
Warrant Shares, will, upon issuance and, if applicable, payment of the
applicable Exercise Price, be duly authorized, validly issued, fully paid and
nonassessable, and free of all liens and encumbrances, except for restrictions
on transfer provided for herein or under applicable federal and state securities
laws.

     3.   ADJUSTMENT OF EXERCISE PRICE AND NUMBER OF SHARES.  The Exercise Price
and the total number of Warrant Shares shall be subject to adjustment from time
to time upon the occurrence of certain events described in this Section 3.  Upon
each adjustment of the Exercise Price, the Holder of this Warrant shall
thereafter be entitled to purchase, at the Exercise Price resulting from such
adjustment, the number of shares obtained by multiplying the Exercise Price in
effect immediately prior to such adjustment by the number of shares purchasable
pursuant hereto immediately prior to such adjustment, and dividing the product
thereof by the Exercise Price resulting from such adjustment.

          3.1  SUBDIVISION OR COMBINATION OF STOCK.  In case the Company shall
at any time subdivide its outstanding shares of Common Stock into a greater
number of shares, the Exercise Price in effect immediately prior to such
subdivision shall be proportionately reduced and the number of Warrant Shares
issuable hereunder proportionately increased, and conversely, in case the
outstanding shares of the Common Stock of the Company shall be combined into a
smaller number of shares, the Exercise Price in effect immediately prior to such
combination shall be proportionately increased and the number of Warrant Shares
issuable hereunder proportionately decreased.

          3.2  RECLASSIFICATION.  If any reclassification of the capital stock
of the Company or any reorganization, consolidation, merger, or any sale, lease,
license, exchange or other transfer (in one transaction or a series of related
transactions) of all or substantially all, of the business and/or assets of the
Company (the "Reclassification 

                                       3
<PAGE>
 
Events") shall be effected in such a way that holders of Common Stock shall be
entitled to receive stock, securities, or other assets or property, then, as a
condition of such Reclassification Event lawful and adequate provisions shall be
made whereby the Holder hereof shall thereafter have the right to purchase and
receive (in lieu of the shares of Common Stock of the Company immediately
theretofore purchasable and receivable upon the exercise of the rights
represented hereby) such shares of stock, securities, or other assets or
property as may be issued or payable with respect to or in exchange for a number
of outstanding shares of such Common Stock equal to the number of shares of such
stock immediately theretofore purchasable and receivable upon the exercise of
the rights represented hereby. In any Reclassification Event, appropriate
provision shall be made with respect to the rights and interests of the Holder
of this Warrant to the end that the provisions hereof (including, without
limitation, provisions for adjustments of the Exercise Price and of the number
of Warrant Shares), shall thereafter be applicable, as nearly as may be, in
relation to any shares of stock, securities, or assets thereafter deliverable
upon the exercise hereof.

          3.3  NOTICE OF ADJUSTMENT.  Upon any adjustment of the Exercise Price
or any increase or decrease in the number of Warrant Shares, the Company shall
give written notice thereof, by first class mail postage prepaid, addressed to
the registered Holder of this Warrant at the address of such Holder as shown on
the books of the Company.  The notice shall be prepared and signed by the
Company's President and Chief Executive Officer and shall state the Exercise
Price resulting from such adjustment and the increase or decrease, if any, in
the number of shares purchasable at such price upon the exercise of this
Warrant, setting forth in reasonable detail the method of calculation and the
facts upon which such calculation is based.

     4.   NO VOTING OR DIVIDEND RIGHTS.  Nothing contained in this Warrant shall
be construed as conferring upon the holder hereof the right to vote or to
consent to receive notice as a shareholder of the Company on any other matters
or any rights whatsoever as a shareholder of the Company.  No dividends or
interest shall be payable or accrued in respect of this Warrant or the interest
represented hereby or the shares purchasable hereunder until, and only to the
extent that, this Warrant shall have been exercised.

     5.   COMPLIANCE WITH SECURITIES ACT; TRANSFERABILITY OF WARRANT;
DISPOSITION OF SHARES OF STOCK.

          5.1  COMPLIANCE WITH SECURITIES ACT.  The Holder of this Warrant, by
acceptance hereof, agrees that this Warrant and the Warrant Shares to be issued
upon exercise hereof are being acquired for investment and that it will not
offer, sell, or otherwise dispose of this Warrant or any Warrant Shares except
under circumstances which will not result in a violation of the Securities Act
of 1933, as amended (the "Act") or any applicable state securities laws.  The
Holder agrees that the Company is under no 

                                       4
<PAGE>
 
obligation to register the Warrants and the Warrant Shares, and Holder
acknowledges that the Company does not intend to cause such a registration. This
Warrant and all Warrant Shares shall be stamped or imprinted with a legend in
substantially the following form:

          THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
1933, AS AMENDED OR THE SECURITIES OR BLUE SKY LAWS OF ANY STATE.  THEY MAY NOT
BE SOLD, OFFERED FOR SALE, PLEDGED, OR HYPOTHECATED IN THE ABSENCE OF A
REGISTRATION STATEMENT IN EFFECT WITH RESPECT TO THE SECURITIES UNDER SUCH ACT
OR AN OPINION OF COUNSEL SATISFACTORY TO THE COMPANY THAT SUCH REGISTRATION IS
NOT REQUIRED, OR UNLESS SOLD PURSUANT TO RULE 144 OF SUCH ACT.


          5.2  ACCESS TO INFORMATION; PRE EXISTING RELATIONSHIP.  Holder has had
the opportunity to ask questions of, and to receive answers from, appropriate
executive officers of the Company with respect to the terms and conditions of
the transactions contemplated hereby and with respect to the business, affairs,
financial condition and results of operations of the Company.  Holder has had
access to such financial and other information as is necessary in order for
Holder to make a fully informed decision as to investment in the Company, and
has had the opportunity to obtain any additional information necessary to verify
any of such information to which Holder has had access.  Holder further
represents and warrants that he has either (i) a pre-existing relationship with
the Company or one or more of its officers or directors consisting of personal
or business contacts of a nature and duration which enable him to be aware of
the character, business acumen and general business and financial circumstances
of the Company or the officer or director with whom such relationship exists or
(ii) such business or financial expertise as to be able to protect his own
interests in connection with the purchase of the Shares.

          5.3  WARRANT TRANSFERABLE.  Subject to compliance with Section 5.4
below and the applicable federal and state securities laws under which this
Warrant was purchased, this Warrant and all rights hereunder are transferable,
in whole or in part, without charge to the Holder (except for transfer taxes),
upon surrender of this Warrant properly endorsed; provided, however, that the
Holder shall notify the Company in writing in advance of any proposed transfer
and shall not transfer this Warrant or any rights hereunder to any person or
entity which is then engaged in a business that in the reasonable judgment of
the Company is in direct competition with the Company.

          5.4  DISPOSITION OF WARRANT SHARES AND COMMON STOCK.  With respect to
any offer, sale, or other disposition of the Warrant or any Warrant Shares, the
Holder hereof and each subsequent Holder of this Warrant agrees to give written
notice to the 

                                       5
<PAGE>
 
Company prior thereto, describing briefly the manner thereof, together with a
written opinion of such Holder's counsel, if reasonably requested by the
Company, to the effect that such offer, sale or other disposition may be
effected without registration or qualification (under the Act as then in effect
or any federal or state law then in effect) of such Warrant or Warrant Shares,
as the case may be, and indicating whether or not under the Act certificates for
such Warrant or Warrant Shares to be sold or otherwise disposed of require any
restrictive legend as to applicable restrictions on transferability in order to
insure compliance with the Act. Promptly upon receiving such written notice and
opinion, the Company, as promptly as practicable, shall notify such Holder that
such Holder may sell or otherwise dispose of such Warrant or Warrant Shares, all
in accordance with the terms of the notice delivered to the Company. If a
determination has been made pursuant to this Section 5.4 that the opinion of the
counsel for the Holder is not reasonably satisfactory to the Company, the
Company shall so notify the Holder promptly after such determination has been
made. Notwithstanding the foregoing, such Warrant or Warrant Shares may be
offered, sold or otherwise disposed of in accordance with Rule 144 under the
Act, provided that the Company shall have been furnished with such information
as the Company may request to provide reasonable assurance that the provisions
of Rule 144 have been satisfied. Each certificate representing the Warrant or
Warrant Shares thus transferred (except a transfer pursuant to Rule 144) shall
bear a legend as to the applicable restrictions on transferability in order to
ensure compliance with the Act, unless in the aforesaid opinion of counsel for
the Holder, such legend is not required in order to ensure compliance with the
Act. The Company may issue stop transfer instructions to its transfer agent in
connection with such restrictions.

     6.   MODIFICATION AND WAIVER.  This Warrant and any provision hereof may be
changed, waived, discharged, or terminated only by an instrument in writing
signed by the party against which enforcement of the same is sought.

     7.   NOTICES.  Any notice, request, or other document required or permitted
to be given or delivered to the Holder hereof or the Company shall be delivered
or shall be sent by certified mail, postage prepaid, to each such Holder at its
address as shown on the books of the Company or to the Company at the address
indicated therefor in the first paragraph of this Warrant or such other address
as either may from time to time provide to the other.

     8.   OTHER NOTICES.  If at any time:

          (1) the Company shall declare any cash dividend upon its Common Stock;

                                       6
<PAGE>
 
          (2) the Company shall declare any dividend upon its Common Stock
payable in stock or make any special dividend or other distribution to the
holders of its Common Stock;

          (3) the Company shall offer for subscription pro rata to the holders
of its Common Stock any additional shares of stock of any class or other rights;

          (4) there shall be any capital reorganization or reclassification of
the capital stock of the Company, or consolidation or merger of the Company
with, or sale of all or substantially all of its assets to, another corporation;
or

          (5) there shall be a voluntary or involuntary dissolution,
liquidation, or winding-up of the Company;

then, in any one or more of said cases, the Company shall give, by first class
mail, postage prepaid, addressed to the Holder of this Warrant at the address of
such Holder as shown on the books of the Company, (a) at least 10 days' prior
written notice of the date on which the books of the Company shall close or a
record shall be taken for such dividend, distribution, or subscription rights or
for determining rights to vote in respect of any such reorganization,
reclassification, consolidation, merger, sale, dissolution, liquidation, or
winding-up, and (b) in the case of any such reorganization, reclassification,
consolidation, merger, sale, dissolution, liquidation or winding-up, at least 10
days' prior written notice of the date when the same shall take place; provided,
however, that the Holder shall make a best efforts attempt to respond to such
notice as early as possible after the receipt thereof.  Any notice given in
accordance with the foregoing clause (a) shall also specify, in the case of any
such dividend, distribution, or subscription rights, the date on which the
holders of Common Stock shall be entitled thereto.  Any notice given in
accordance with the foregoing clause (b) shall also specify the date on which
the holders of Common Stock shall be entitled to exchange their Common Stock for
securities or other property deliverable upon such reorganization,
reclassification, consolidation, merger, sale, dissolution, liquidation,
winding-up or conversion, as the case may be.

     9.   GOVERNING LAW.  This Warrant shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the State of California.

     10.  LOST WARRANTS.  The Company represents and warrants to the Holder
hereof that upon receipt of evidence reasonably satisfactory to the Company of
the loss, theft, destruction, or mutilation of this Warrant and, in the case of
any such loss, theft or destruction, upon receipt of an indemnity reasonably
satisfactory to the Company, or in the case of any such mutilation upon
surrender and cancellation of such Warrant, the 

                                       7
<PAGE>
 
Company, at its expense, will make and deliver a new Warrant, of like tenor, in
lieu of the lost, stolen, destroyed or mutilated Warrant.

     11.  FRACTIONAL SHARES.  No fractional shares shall be issued upon exercise
of this Warrant.  The Company shall, in lieu of issuing any fractional share,
pay the Holder entitled to such fraction a sum in cash equal to such fraction
(calculated to the nearest 1/100th of a share) multiplied by the then effective
Exercise Price on the date the Form of Subscription is received by the Company.

     12.  NO IMPAIRMENT.  The Company will not, by charter amendment or by
reorganization, transfer of assets, consolidation, merger, dissolution, issue or
sale of securities, or any other voluntary action, avoid or seek to avoid the
observance or performance of any terms of this Warrant, but will at all times in
good faith assist in the carrying out of all such terms and in the taking of all
such action as may be necessary or appropriate in order to protect the rights of
the Holder against impairment.  Upon the request of the Holder, the Company will
at any time during the period this Warrant is outstanding acknowledge in
writing, in form satisfactory to Holder, the continued validity of this Warrant
and the Company's obligations hereunder.

     13.  SUCCESSORS AND ASSIGNS.  This Warrant and the rights evidenced hereby
shall inure to the benefit of and be binding upon the successors of the Company
and the Holder.  The provisions of this Warrant are intended to be for the
benefit of all Holders from time to time of this Warrant, and shall be
enforceable by any such Holder.

                                       8
<PAGE>
 
          IN WITNESS WHEREOF, the Company has caused this Warrant to be duly
executed by its officer, thereunto duly authorized as of this      day 
                                                              ----
of          ,     .
   ---------  ----

                                NEUROBIOLOGICAL TECHNOLOGIES, INC.,
                                a Delaware corporation


                                By:  
                                    ----------------------------------------

                                Name:      
                                      --------------------------------------

                                Title:                                   
                                       -------------------------------------

                                       9
<PAGE>
 
                             FORM OF SUBSCRIPTION

(To be signed only upon exercise of Warrant)

To:  Neurobiological Technologies, Inc.

[Please mark one box]

[ ]The undersigned, the holder of the attached Common Stock Warrant, hereby
   irrevocably elects to exercise the purchase right represented by such Warrant
   for, and to purchase thereunder, (1)                           shares of
                                    -----------------------------          
   Common Stock of Neurobiological Technologies, Inc. (the "Company") and
   herewith makes payment of $          therefor, and requests certificates for
                               --------
   such shares be issued in the name of, and delivered to,                     
                                                           --------------------
   whose address is                                                           .
                    ----------------------------------------------------------

   The undersigned, the holder of the attached Common Stock Warrant, hereby
   irrevocably elects to exercise the purchase right represented by such Warrant
   for, and to purchase thereunder, (1)                           shares of
                                    -----------------------------          
   Common Stock of the Company and herewith elects to pay for such shares by
   reducing the number of shares issuable thereunder in accordance with Section
   1.2 thereof.  The undersigned hereby authorizes the Company to make the
   required calculation under Section 1.2 of the Warrant.

     The undersigned represents that it is acquiring such Common Stock for its
own account for investment and not with a view to or for sale in connection with
any distribution thereof.

DATED:               ,       
       --------------  -----


                              --------------------------------------------------
                              (Signature must conform in all respects to name of
                              Holder as specified on the face of the Warrant)


                              Name:                                        
                                    --------------------------------------------
 
                              Title:                                       
                                     -------------------------------------------

                                       10
<PAGE>
 
(1)  Insert here the number of shares called for on the face of the Warrant (or,
in the case of a partial exercise, the portion thereof as to which the Warrant
is being exercised), in either case without making any adjustment for any stock
or other securities or property or cash which, pursuant to the adjustment
provisions of the Warrant, may be deliverable upon exercise.

                                       11