Secondary depression, concepts

On balance, these actions could support a decrease rather than an increase in the functional state of CNS NE transmission, because depression can be conceptualized as a state of supersensitive catecholamine receptors secondary to decreased NE availability. This reasoning is consistent with the original hypothesis of diminished NE functioning, with antidepressants returning receptors to a more normal state of sensitivity. Siever and Davis ( 41) further elaborated on this concept by suggesting the possibility of dysregulation in the homeostatic mechanisms of one or more neurotransmitter systems, culminating in an unstable or erratic output. 

Both the inhaled and the intravenous anesthetics can depress spontaneous and evoked activity of neurons in many regions of the brain. Older concepts of the mechanism of anesthesia evoked nonspecific interactions of these agents with the lipid matrix of the nerve membrane (the so-called Meyer-Overton principle)—interactions that were thought to lead to secondary changes in ion flux. More recently, evidence has accumulated suggesting that the modification of ion currents by anesthetics results from more direct interactions with specific nerve membrane components. The ionic mechanisms involved for different anesthetics may vary, but at clinically relevant concentrations they appear to involve interactions with members of the ligand-gated ion channel family. 

As more was written on the subject of negative symptoms the literature became blurred as to whether the symptoms discussed were related to state or trait (Sommers, 1985). To refine the concept, negative symptoms resulting from treatment (e.g., Parkinsonism related to neuroleptics), psychosis (e.g., elective mutism related to paranoia), institutionalization/monotonous routine, and/or related to depression were referred to as secondary negative symptoms (Carpenter et al., 1985). In contrast, primary negative symptoms were due to the illness itself. These enduring traits were labeled deficit symptoms (Carpenter et al., 1985). 

Robins E, Guze SB (1972) Classification of affective disorders The primary-secondary, the endogenous-reactive, and the neurotic-psychotic concepts. In Recent Advances in Psychobiology of the Depressive Illnesses, Proceedings of a Workshop Sponsored by the NIMH (Williams TA, Katz MM, Shield JA, eds), Washington, D.C. U.S. GPO. 

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