Regional studies of brain biogenic amines in castrated muricidal and non-muricidal wistar rats

Abstract

Castrated Wistar rats were isolated for 8 months and their muricidal behavior was investigated. Significantly fewer (35%) of such rats became muricidal (CM) compared to controls. The steady-state levels of 5-HT, 5-HIAA, DA, DOPAC, and NE, as well as the changes in synthesis or utilization rats of 5-HT and DA, were analyzed in 15 brain areas derived from CM rats and non-muricidal (CNM) control subjects. In CM rats, higher 5-HT levels were recorded in 5 areas considered to be involved in muricidal behavior: raphe, amygdala, olfactory tubercles, olfactory bulbs, and striatum. The alterations of serotonergic neurotransmission in castrated muricidal rats differ strikingly from those observed in non-castrated muricidal rats. An increase of 5-HT level and in the 5-HT synthesis index as well as a lower 5-HT utilization index were recorded in the raphe of CM rats. Our data suggest that the decrease of 5-HT levels generally said to be the main alteration in the muricidal rat's brain has to be reconsidered. Increased DA levels were observed in CM rats: raphe (50%), amygdala, olfactory tubercles, striatum, and septum (40%), while DA was decreased in cortical areas. There were slight increases of DA synthesis indices in the septum, olfactory tubercles and striatum with a decreased utilization index in the olfactory tubercles. Few alterations in NE levels were observed in CM rats: a decrease in the olfactory tubercles, superior colliculus, and striatum and an increase in temporal cortex. The monoaminergic alterations correlate with the modulation of muricidal behavior. Some areas (the olfactory tubercles, raphe, striatum, and temporal cortex) seem to be particularly involved. © 1992 Wiley-Liss, Inc.