Is there any way to make a sampling rate reduction in the frequency domain?
Yes, you can do what you're looking for. Think about what happens in the frequency domain when you downsample a signal in the time domain: the spectrum "folds over" on top of itself and sums, the well-known aliasing effect. If your signal is already sufficiently bandlimited, then you can obtain the downsampled time-domain signal without computing the samples that you would subsequently throw out.

Given a signal $x[n], n = 0, 1, \ldots , N-1 $ that has DFT $X[k], k = 0, 1, \ldots , N-1$, a new signal $x_d[n]$ that is $x[n]$ decimated by a factor $D$ can be generated by:

$$
X_d[k&#39;] = \sum_{d=0}^{D-1} X[k&#39; + d\frac{N}{D}], k&#39; = 0, 1, \ldots , \frac{N}{D} - 1
$$

$$
x_d[n] = IDFT(X_d[k&#39;])
$$

The inverse DFT (and subsequently $x_d[n]$) is of length $\frac{N}{D}$. This method is sometimes referred to as "stack and add".