Organization of cortical, basal forebrain, and hypothalamic afferents to the parabrachial nucleus in the rat

Abstract

In a previous study (Herbert et al., J. Comp. Neurol. [1990];293:540-580), we demonstrated that the ascending afferent projections from the medulla to the parabrachial nucleus (PB) mark out functionally specific terminal domains within the PB. In this study, we examine the organization of the forebrain afferents to the PB. The PB was found to receive afferents from the infralimbic, the lateral prefrontal, and the insular cortical areas; the dorsomedial, the ventromedial, the median preoptic, and the paraventricular hypothalamic nuclei; the dorsal, the retrochiasmatic, and the lateral hypothalamic areas; the central nucleus of the amygdala; the substantia innominata; and the bed nucleus of the stria terminalis. In general, forebrain areas tend to innervate the same PB subnuclei from which they receive their input. Three major patterns of afferent termination were noted in the PB; these corresponded to the three primary sources of forebrain input to the PB: the cerebral cortex, the hypothalamus, and the basal forebrain. Hypothalamic afferents innervate predominantly rostral portions of the PB, particularly the central lateral and dorsal lateral subnuclei. The basal forebrain projection to the PB ends densely in the external lateral and waist subnuclei. Cortical afferents terminate most heavily in the caudal half of the PB, particularly in the ventral lateral and medial subnuclei. In addition, considerable topography organization was found within the individual projections. For example, tuberal lateral hypothalamic neurons project heavily to the central lateral subnucleus and lightly to the waist area; in contrast, caudal lateral hypothalamic neurons send a moderately heavy projection to both the central lateral and waist subnuclei. Our results show that the forebrain afferents of the PB are topographically organized. These topographical differences may provide a substrate for the diversity of visceral functions associated with the PB.

Ascending Projections from the Area Postrema and the Nucleus of the Solitary Tract of Suncus Murinus

“…Our findings in the present study are entirely consistent with their results. In the rat and golden hamster, the external subdivision of the LPb was reported to project extensively to the basal forebrain region including to the Amy and the hypothalamus (Fulwiler and Saper, 1984;Moga et aL, 1990;Halsell, 1992). Based on a physiological study, electrical or chemical stimulation of this region should produce profound pressor, tachycardic, and tachypneic responses in the rat .…”

Modulation of activity of gustatory neurons in the hamster parabrachial nuclei by electrical stimulation of the ventroposteromedial nucleus of the thalamus

“…From the NST, ascending gustatory fibers project to third-order taste cells within the PbN of the pons (7,22,42,46,(53)(54)(55)87). Two separate routes carry taste information from the PbN further to the forebrain taste areas and cortex: the ventral forebrain pathway that involves the central nucleus of the amygdala (CeA), the lateral hypothalamus (LH), the bed nucleus of the stria terminalis (BNST), the substantia innominata (3,12,16,21,31,33,34,41,47,63,64,71); and the thalamocortical pathway that is characterized by the involvement of the bilateral VPMpc, which, in turn, carries taste information to the gustatory cortex (GC) (5,25,45,48,51).The PbN is a critical neural substrate for a number of taste-guided behavioral or physiological responses, including conditioned taste aversion learning (CTA), gastric distension, and sodium appetite. It has been demonstrated that a subpopulation of neurons in the PbN can be coactivated by both gustatory and vagal (hepatic) stimulation (26) or gustatory and gastric distension (1), indicating that the PbN is the locus of integration for gustatory and other vagal afferent inputs.…”

Role of the Septum in the Excitatory Effect of Corticotropin-Releasing Hormone on the Acoustic Startle Reflex

“…Second, studies of immediate early gene activation have shown that various limbic structures, including the lateral septum, are activated by intracerebroventricular CRH (Arnold et al, 1992;Imaki et al, 1993). Third, the septum shows strong connections to areas implicated in stress responses, such as the paraventricular nucleus of the hypothalamus, the dorsal raphe nucleus, and the locus coeruleus (Swanson and Cowan, 1979;Silverman et al, 1981;Sawchenko and Swanson, 1983;Moga et al, 1991;Staiger and Nürnberger, 1991). The medial septum has a direct projection to the amygdala, whereas the lateral septum has both a direct projection and a more extensive indirect projection to the amygdala (Meibach and Siegel, 1977;Russchen, 1982;Dudley et al, 1990;Volz et al, 1990;Staiger and Nürnberger, 1991).…”