Angular throws is not a function when actually is

Question

Hello: I'm making a long polling with angular js and everything works until I make a getResponse function the program involves a) a main (at the bottom) b) a constructor to a service c) "the famous" getResponse which is a function of the service d) A simple console log to process response e) A setPolling service which is the loop f) Set response which makes a response to the service g) A simple directive

Can you tell why is throwing this.getResponse is not a function when actually is... ? heres the code

var DbService = function($http, $window, $interval) {
    this.http_ = $http;
    this.interval_ = $interval;
    this.window_ = $window;
    this.db = null;
};

DbService.prototype.getResponse = function() {
    this.http_({
        method: 'get',
        url: 'dependencies/request.php',
        data: ""
        }).then(function successCallback(response) {
            this.setResponse(response);
        }, function errorCallback(response) {
            console.log("Err response");
    });
};

DbService.processResponse = function(response) {
    console.log(this.response_);
};

DbService.prototype.setPolling = function() {
    this.interval_(function(){
        console.log("Hi World!");
        this.response_ = this.getResponse();
        this.processResponse(this.response_);
    }, 10000);
};

DbService.prototype.setResponse = function(response) {
    this.response_ = response;
};

var informAction = function($scope, DbService) {
    return {
        restrict: 'C',
        link: function($scope, elem, attr, ctrl) {
            action = DbService.getResponse();
            $scope.consmensaje += "Accion: " + action.data['action'] + "\n";
        }
    };
};

var MainController = function($http, $window, $interval, DbService) {
    this.http_ = $http;
    this.window_ = $window;
    this.interval_ = $interval;
    this.DbService_ = DbService;
    console.log("Dentro de Controller");
    this.DbService_.setPolling();
};


function main() {
    console.log("Comenzando");
    var app = angular.module('consola', []);
    app.service('DbService', DbService);
    app.controller(
      'MainController',
      ['$scope', '$http', '$interval', 'DbService',
        MainController]);
    app.directive('informAction', ['$scope', 'DbService', informAction]);
}

main();