We consider a cognitive radio network in which a base station provides opportunistic unlicensed spectrum access for secondary base stations to transmit data to their subscribers. The primary user may decide to release some parts of its bandwidth for the use of secondary users. As a result, secondary users pay a fee to the primary user based on the interference they make. Considering cognitive radios, we propose and analyze a framework, whereby a primary user has the possibility to release its channel to a secondary network in exchange for money. On one Hand the primary user attempts to maximize its payoff, while on the other hand, secondary users try to minimize the money they pay to the primary user and maximize their own payoff. The investigated model is conveniently cast in the framework of Stack- elberg games. Our simulation consists of two major parts. First there is a negotiation among the secondary network nodes about the distribution of secondary channels. In this part, we use social optimum of secondary network as the negotiation result. Second, we consider a Stackelberg game between the primary user and the secondary network in which the primary user wants to maximize its payoff by increasing its cost or the number of channels available for the secondary network.