Rao, M. L., & Oades, R. D., (2001). Biochemical hypotheses of negative symptoms revisited: an update. World Journal of Biological Psychiatry, 2, 105..

Early studies from postmortem and cerebrospinal fluid analyses reported associations of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) - related changes with negative vs. positive syndromes, patients with/without dementia, and CNS atrophy suggested through ventricular enlargement.

More recently the increased ratio of DA to 5-HT metabolites (HVA/5-HIAA) recorded peripherally after atypical antipsychotic treatment (that improves in part the negative as well as the positive symptoms) has been related to their affinity for dual actions at the 5-HT2a and DA D2-family of binding sites.

The interactions of DA with 5-HT and with glutamate and adenosine were reviewed in the context of stabilizing activity in the cortical-striatal-thalamic circuit in order to achieve clinical improvement.

see also
Oades et al. (2001) World J Biol Psychiat, 2, 286 (poster at this meeting), and
Carlsson et al (1999) Biol Psychiat 46, 1388-1395
Garver et al. (1999) Neuropsychopharmacol, 21, 82-92
Zhang et al. (2001) J. Psychiatr Res, 35, 23-38.