Constitutive Nitric Oxide Synthase Activity in the Prefrontal Cortex of Rats as an Index of Emotional State Before Death

The prefrontal cortex (PFC), as a part of the ’limbic circuit’, plays a fundamental role in emotional and cognitive processes (Lane et al., 1997; Maguire et al., 1998). This has been shown both in experimental animal models and in humans, using modem imaging techniques (Lane et al., 1997; Maguire et al., 1998; Middleton & Strick, 1997). Numerous excitatory amino acids (EAA) neurons are present in PFC, and glutamate plays a key role in excitatory neurotransmission in the central nervous system (McDonald, 1996). Nitric oxide (NO) plays a significant, indirect role in the stimulation of glutamate receptors, particularly the ionotropic (iGluR) and metabotropic (mGluR) glutamate receptor types. The stimulation of both types of glutamate receptors increases after the generation of NO (Gage et al, 1997; Kendrick et al., 1997), indicating that NO may act as a modulator of glutamatergic neurotransmission. Both glutamate and the activity of the enzyme NO-synthase (NOS) respond to noxious, stressful environmental influences. An increased level of