The provisions of § 38a-119 shall not apply to any purchase and sale, or sale and purchase, and the provisions of § 38a-120 shall not apply to any sale, of an equity security of a domestic stock insurance company not then or theretofore held by him in any investment account, by a dealer in the ordinary course of his business and incident to the establishment or maintenance by him of a primary or secondary market for such security. The commissioner may, by such regulations as he deems necessary or appropriate in the public interest, define and prescribe terms and conditions with respect to securities held in an investment account and transactions made in the ordinary course of business and incident to the establishment or maintenance of a primary or secondary market.