The credit conditions have a direct influence on the investment and consumption decisions made by the agents, considering that they usually can`t borrow paying only the basic interest rate fixed by the monetary authority. That being said, movements in the credit supply, interpreted in this work as changes in the credit spread for a given Selic rate, change the relative price of future consumption and have an impact on aggregate demand. Through the estimation of a VAR (Vector Auto Regression) for the Brazilian economy we find empirical evidence that a shock to the credit supply has a significant impact on economic activity. Afterwards, we estimate a central bank`s reaction function, and the results suggest that the monetary authority responds to a fall in the credit spread by hiking its interest rate target, ceteris paribus, in order to compensate the change in the intertemporal trade-off faced by the agents.