Eloquent/Laravel5 linking distant relations ("hasOneThrough") - laravel-5

Question

The question in short:
"pages" and "tasks" have a many-to-many relationship linked by the pivot table "page_tasks". The table "responses" is linked to that pivot table by the foreign key "page_task_id".
Now I want to be able to access the page and the task a response belongs to directly with Eloquent. However the hasManyThrough function does not work, as it exspects the foreign_keys at different places:
public function task(){
return $this->hasManyThrough('PageTask', 'Task', 'page_task_id', 'task_id');
}
Unknown column 'tasks.page_task_id' in 'field list'
This means that eloquent exspects the task table having a foreign key page_task_id pointing to page_tasks. But in my model the page_tasks table has a foreign key task_id pointing to tasks. How do I tell eloquent that fact?
An other approach I tried was to use existing relations that were previously defined:
public function task(){
return $this->page_task->task();
}
This however tells me that there is no methoid called "task".
What would the recommended way be to achieve this? What am I doing wrong?
Here are some more details if needed:
"pages" and "tasks" have a many-to-many relationship with pivot table page_tasks linking it.
Page-Model:
class Page extends Model {
public function tasks(){
return $this->belongsToMany('Task', 'page_tasks');
}
}
Task-Model:
class Task extends Model {
public function pages()
{
return $this->belongsToMany('Page', 'page_tasks');
}
}
This works fine.
Response-Model looks like this
class Response extends Model {
protected $fillable = [
'page_task_id',
];
public function page_task(){
return $this->belongsTo('App\PageTask', 'page_tasks');
}
public function task(){
??????
}
}
PageTask-Model looks like this:
class PageTask extends Model {
protected $fillable = [
'page_id',
'task_id',
];
public function page(){
return $this->belongsTo('Page');
}
public function task(){
return $this->belongsTo('Task');
}
public function responses(){
return $this->hasMany('Response');
}
}