...
public float sensitivityHor = 9.0f;
public float sensitivityVert = 9.0f;  

public float minimumVert = -45.0f;
public float maximumVert = 45.0f;

private float _rotationX = 0;     
 
void Update() {
  if (axes == RotationAxes.MouseX) {
    transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityHor, 0);
  }
  else if (axes == RotationAxes.MouseY) {
    _rotationX -= Input.GetAxis("Mouse Y") * sensitivityVert; 
    _rotationX = Mathf.Clamp(_rotationX, minimumVert, maximumVert); 

    float rotationY = transform.localEulerAngles.y;          

    transform.localEulerAngles = new Vector3(_rotationX, rotationY, 0);
  }
...
