NEURONAL CELL-DEATH DURING SEXUAL-DIFFERENTIATION AND LATERALIZATION OF VOCAL COMMUNICATION

A rodent analogy has been established to investigate the neural mechan isms occurring during sexual differentiation and lateralization. A sex ually dimorphic hypothalamic nucleus (SDApc) is closely associated wit h a stereotyped courtship vocalisation in male gerbils. Stereological analysis of SDApc cytoarchitecture reveals that neuron number and nucl ear volume are asymmetric in male adults. Strikingly, neuron number on the left side of the SDApc correlates significantly with the rate of the courtship call in males. Exogenous testosterone treatment in femal e neonates masculinises and lateralises SDApc structure and function. Neuronal programmed cell death (apoptosis), manifested in SDApcs of ne onates, is more frequent in females. Significantly, apoptosis in males is lateralised, as revealed by lateral asymmetry of neuron number at postnatal day 16. It is concluded that neuroendocrine-dependent, sexua l differentiation and lateralization are concurrent and influenced by apoptotic mechanisms. It is suggested that apoptosis is the result of a genetically-driven device, inherent in postmitotic, undifferentiated cells which may have recently migrated into the SDApc. The genomic me chanism inducing lateralised apoptosis is apparently activated only ne onatally in males. (C) 1998 Elsevier Science Ltd. All rights reserved.