The intercalated cell masses project to the central and medial nuclei of the amygdala in cats

In order to study the efferent projections of the intercalated cell masses within the amygdaloid complex, iontophoretic injections of cholera toxin B subunit were performed in several amygdaloid nuclei of the centromedial and basolateral groups in cats. Analysis of the ensuing retrograde labeling revealed that the main intra-amygdaloid targets of the intercalated cell masses are the central and medial nuclei. Most intercalated neurons projecting to the medial nucleus were found in the larger, rostrally located intercalated cell masses. In contrast, the majority of intercalated cells projecting to the central medial and central lateral nuclei were found in the smaller, caudally located intercalated cell masses. In addition, evidence for weaker projections to the basolateral nucleus and other intercalated cell masses was obtained. In light of previous immunohistochemical results showing that GABAergic cells represent the main cell type in the intercalated cell masses, these results imply that the intercalated cell masses constitute an important source of GABAergic input to the centromedial complex. The significance of this finding lies in the fact that the intercalated cell masses are located at the interface between the basolateral nuclear group and the centromedial complex, the main route through which the amygdaloid complex can directly influence hypothalamic and brainstem centers involved in the elaboration of autonomic responses and species-specific emotional behaviors.

[1]  C D Gilbert,et al.  Aspartate and glutamate as possible neurotransmitters in the visual cortex , 1981, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[2]  Bruce S. Kapp,et al.  Electrophysiological characteristics of amygdaloid central nucleus neurons in the awake rabbit , 1985, Brain Research Bulletin.

[3]  T. Tömböl,et al.  A golgi study of the amygdaloid complex in the cat. , 1972, Acta neurobiologiae experimentalis.

[4]  L. Swanson,et al.  The organization of projections from the central nucleus of the amygdala to brainstem sites involved in central autonomic regulation: A combined retrograde transport-immunohistochemical study , 1984, Brain Research.

[5]  M. J. Christie,et al.  Excitatory amino acid projections to the nucleus accumbens septi in the rat: A retrograde transport study utilizingd[3H]aspartate and [3H]GABA , 1987, Neuroscience.

[6]  Joseph E LeDoux,et al.  Projections from the lateral nucleus to the basal nucleus of the amygdala: A light and electron microscopic PHA‐L study in the rat , 1992, The Journal of comparative neurology.

[7]  H. Higashi,et al.  Synaptic responses of guinea pig and rat central amygdala neurons in vitro. , 1991, Journal of Neurophysiology.

[8]  G. Holstege.  Subcortical Limbic System Projections To Caudal Brainstem And Spinal Cord. , 1990 .

[9]  B. Kaada,et al.  Brain mechanisms related to aggressive behavior. , 1967, UCLA forum in medical sciences.

[10]  J. Johnston.  Further contributions to the study of the evolution of the forebrain , 1923 .

[11]  M. Cassell,et al.  Intrinsic GABAergic neurons in the rat central extended amygdala , 1993, The Journal of comparative neurology.

[12]  J. Price,et al.  A description of the amygdaloid complex in the rat and cat with observations on intra‐amygdaloid axonal connections , 1978, The Journal of comparative neurology.

[13]  F. T. Russchen,et al.  Amygdalopetal projections in the cat. I. Cortical afferent connections. A study with retrograde and anterograde tracing techniques , 1982, The Journal of comparative neurology.

[14]  A. Routtenberg,et al.  Subfornical organ: Duration of dipsogenic action of angiotensin-II , 1977, Neuroscience Letters.

[15]  A. Brodal.  The amygdaloid nucleus in the rat , 1947, The Journal of comparative neurology.

[16]  H. Stephan,et al.  Quantitative comparison of the amygdala in insectivores and primates. , 1977, Acta anatomica.

[17]  C. Fox.  Certain basal telencephalic centers in the cat , 1940 .

[18]  M. Frotscher,et al.  Organization and synaptic interconnections of GABAergic and cholinergic elements in the rat amygdaloid nuclei: Single‐ and double‐ immunolabeling studies , 1989, The Journal of comparative neurology.

[19]  C. Gilbert,et al.  Aspartate and glutamate as possible neurotransmitters of cells in layer 6 of the visual cortex , 1980, Nature.

[20]  F. T. Russchen,et al.  Amygdalopetal projections in the cat. II. Subcortical afferent connections. A study with retrograde tracing techniques , 1982, The Journal of comparative neurology.

[21]  T. Tömböl,et al.  Golgi studies on the amygdaloid nuclei of the cat. , 1975, Journal fur Hirnforschung.

[22]  H. Groenewegen,et al.  Connections of the parahippocampal cortex in the cat. II. Subcortical afferents , 1986, The Journal of comparative neurology.

[23]  Y. Ben-Ari,et al.  Neurochemical mapping of GABAergic systems in the amygdaloid complex and bed nucleus of the stria terminalis , 1978, Brain Research.

[24]  M. Völsch.  Zur vergleichenden Anatomie des Mandelkerns und seiner Nachbargebilde , 1910 .

[25]  J. R. Augustine,et al.  Localization of GABA-like immunoreactivity in the monkey amygdala , 1993, Neuroscience.

[26]  D. Paré,et al.  Distribution of GABA immunoreactivity in the amygdaloid complex of the cat , 1993, Neuroscience.

[27]  Y. Ben‐Ari,et al.  Distribution of GABA‐like immunoreactivity in the rat amygdaloid complex , 1987, The Journal of comparative neurology.

[28]  R. Bandler.  Induction of ‘page’ following microinjections of glutamate into midbrain but not hypothalamus of cats , 1982, Neuroscience Letters.

[29]  O. E. Millhouse.  The intercalated cells of the amygdala , 1986, The Journal of comparative neurology.