Tricyclic antidepressants work on the noradrenalin and serotonin neurotransmitters, therefore your request for something that does not boost serotonin will be difficult. Not to take benzo s is a good choice, as it has addictive effect. A good substitute would be Quetiapine in lower dose, which has a mood stabilizing effect and an effect on anxiety. But it also has an effect on Serotonin. You can also try psychotherapy with a therapist which can make use of CBT to treat anxiety and research also show that therapy combined with suitable tablets works the best for anxiety disorders