Amygdaloid projections to the mesencephalon, pons and medulla oblongata in the cat

Abstract

Amygdalotegmental projections were studied in 26 cats after injections of horseradish peroxidase (HRP) in the diencephalon, midbrain and lower brain stem and in 6 cats after injection of 3H-leucine in the amygdala. Following HRP injections in the posterior hypothalamus, periaqueductal gray (PAG) and tegmentum many retrogradely labeled neurons were present in the central nucleus (CE) of the amygdala, primarily ipsilaterally. Injections of HRP in the posterior hypothalamus and mesencephalon also resulted in the labeling of neurons in the basal nucleus, pars magnocellularis. Following 3H-leucine injections in CE and adjacent structures autoradiographically labeled fibers were present in the stria terminalis and ventral amygdalofugal pathways. In the mesencephalon heavily labeled fiber bundles were located lateral to the red nucleus. Labeled fibers and terminals were distributed to the mesencephalic reticular formation, substantia nigra, ventral tegmental area and PAG. In the pontine and medullary tegmentum the bulk of passing fibers was located laterally in the reticular formation. Many labeled fibers and terminals were distributed to the parabrachial nuclei, locus coeruleus, nucleus subcoeruleus and lateral tegmental fields. Many terminals were also present in the solitary nucleus and dorsal motor nucleus of the vagus nerve. The location of the cells of origin and the distribution of the terminals of the amygdalotegmental projection suggest that this pathway plays an important role in the integration of somatic and autonomic responses associated with affective defense.

Different projections of the central amygdaloid nucleus mediate autonomic and behavioral correlates of conditioned fear

“…Contribution of other projections of the central amygdaloid nucleus In addition to LH and CG, ACE projects to a number of other areas, including BNST, lateral nucleus of the substantia nigra, parabrachial region, nucleus reticularis pontis caudalis, nucleus of the solitary tract, dorsal motor nucleus of the vagus, rostra1 ventral lateral medulla, and spinal cord (e.g., Hopkins and Holstedge, 1978;Krettek and Price, 1978a;Saper, 1979;Price, 198 1;Price and Amaral, 198 1;Schwaber et al, 1982). Results in the present study demonstrate that IBO lesions of the BNST have no effect on either conditioned MAP or freezing responses.…”

“…If the central amygdaloid nucleus (ACE) is an essential link in the pathway mediating the autonomic and behavioral correlates of conditioned fear, it should be possible to disrupt conditioned fear responses by destroying areas to which the central nucleus projects. Studies over the past several years have provided detailed descriptions of the efferent targets of the central nucleus in a number of mammalian species (Hopkins and Holstedge, 1978;Krettek and Price, 1978a, b;Saper, 1979;Price, 1981;Price and Amaral, 198 1;Schwaber et al, 1982;van der Kooy et al, 1984;Cassell et al, 1986). In the present study we have examined the effects of damage to 3 of the areas purported to receive efferents from the central amygdala, including the bed nucleus of the stria terminalis (BNST), the lateral hypothalamic area (LH), and the midbrain central gray (CG) region.…”

The Effects of Locus Coeruleus and Norepinephrine in Methamphetamine Toxicity

“…The main afferents to the LC include projections from the prefrontal cortex (PFC), lateral hypothalamus [38], cerebellum [39], raphe nuclei [40], and amygdala [41]. Furthermore, the LC receives NE afferents from lower medullary A1 and A2 regions [42-44].…”

Bilateral behavioral and regional cerebral blood flow changes during painful peripheral mononeuropathy in the rat

“…Bernard and colleagues (1989Bernard and colleagues ( ,1990Bernard and colleagues ( ,1996 have demonstrated a spino(trigemino)pontoamygdaloid pathway that may be involved with the affective-motivational dimension of pain. Conversely, anatomical and electrophysiological studies indicate the existence of an efferent pathway originating in the amygdala, synapsing within the periaquaductal gray and continuing on to the spinal cord dorsal horn that modulates pain (Hopkins and Holstege 1978;Krettek and Price 1978;Beitz 1982;Watson et al, 1983;Zhang et al, 1991;Bernard et al, 1996;Manning 1998). In addition, the basal ganglia receives nociceptive information through several sources including the amygdala, cingulate cortex, prefrontal cortex and the habenula (Ma and Han, 1991;Cenci et al, 1992;Ma et al, 1992;Chudler and Dong, 1995).…”