Each civic center authority heretofore or hereafter incorporated in any county having a population of more than 500,000, according to the last or any subsequent federal census, pursuant to Sections 45-37-90 to 45-37-90.07, inclusive, is hereby granted the power and authority, in addition to the power and authority heretofore granted by act of the Legislature or by amendment to the constitution, to borrow money from time to time for any corporate purpose and to issue its negotiable promissory note or notes to mature not later than three years from date of issue, as evidence of its obligation to repay the money so borrowed, with interest thereon, such notes to be payable solely (1) from one or more of the sources from which bonds authorized by Sections 45-37-90 to 45-37-90.07, inclusive, or by Amendment 280 to the Constitution of Alabama of 1901, are payable and, if the note or notes shall be issued to provide funds for a purpose for which such bonds are authorized to be issued, also (2) from the proceeds of any like promissory notes or bonds which may be issued to fund or refund such promissory notes. Any such civic center authority shall have the same power and authority with respect to such negotiable promissory notes as those which were granted to it with respect to the issuance of bonds by Section 45–37–90.06 and by Amendment 280 to the Constitution of Alabama of 1901; provided, however, that such promissory notes may be placed or sold at private negotiated sale without competitive bidding, and such negotiable promissory notes may be executed without the seal of such civic center authority being affixed thereto.