Afferent projections to the ventromedial hypothalamic nucleus in a lizard, Gekko gecko.

Afferent projections to the ventromedial hypothalamic nucleus (VMH) of a lizard, Gekko gecko, were studied with wheat germ agglutinin conjugated to horseradish peroxidase. Results indicated that the shell and core areas of the VMH are largely innervated by different telencephalic nuclei but similar brain-stem nuclei. The common brainstem projections include the superior raphe, two isthmal populations (the ventral isthmal nucleus and parvocellular isthmal nucleus), and a dorsal thalamic projection from the posteroventral nucleus. Brainstem projections to the shell but not to the core of the VMH arise from the laterodorsal tegmental nucleus. Telencephalic projections to the VMH core originate from the ventrolateral septum, centromedial DVR, lateral amygdala, medial amygdala, interstitial amygdala, and ventral anterior amygdala. Telencephalic projections to the VMH shell come from the ventral pallidum, the anterior septal nucleus, the dorsal septal nucleus, the striatoamygdalar area, and the ventral posterior amygdala. These results, combined with connectional and topological information from other studies in amphibians, reptiles, and mammals, will be used to suggest homologies between a number of limbic areas, including several amygdalar nuclei.

Afferent projections to the hypothalamus in ranid frogs.

Hypothalamic afferents were examined following applications of wheat germ agglutinin-horseradish peroxidase in the infundibulum of bullfrogs (Rana catesbeiana). Neuronal populations were generally labelled bilaterally, with an ipsilateral predominance. In the telencephalon, most labelled cells were present in the medial pallium, ventral lateral pallium, lateral amygdala, and lateral septal nucleus. A moderate number of cells were found in the medial amygdala and fewer still in the caudal striatum, olfactory tubercle/diagonal band nucleus, medial septal nucleus, and median septum. In the diencephalon, labelled neurons were primarily found in the anterior and central thalamic nuclei, anterior preoptic area, and suprachiasmatic nucleus. Fewer cells were present in the ventral habenular nucleus, anterior division of the lateral thalamic nucleus, posterior thalamic nucleus, ventromedial thalamic nucleus, magnocellular preoptic nucleus, posterior entopeduncular nucleus, and along the medial forebrain bundle. In the midbrain, a few labelled cells were found in the nucleus of the medial longitudinal fasciculus, suprapeduncular nucleus, and posteroventral tegmental nucleus. The secondary isthmal nucleus contained a large number of labelled neurons and moderate numbers of labelled cells were present in the grey medial to nucleus isthmi and in the isthmal raphe. A few lightly labelled cells were also seen in the parabrachial nucleus. Finally, after the largest applications, a few cells were seen in the obex region ventrolateral to the solitary tract.

Afferent projections to the lateral and dorsomedial hypothalamus in a lizard, Gekko gecko.

Afferent projections to the lateral hypothalamic area and dorsomedial hypothalamic nucleus of the lizard Gekko gecko were studied after applications of wheat germ agglutinin conjugated to horseradish peroxidase. Large applications into the hypothalamus labeled several telencephalic populations not observed after smaller injections. These included the rostrolateral area of the dorsal cortex, a sheet of cells deep to the caudal pole of the lateral cortex, the external amygdala, and part of the dorsal ventricular ridge. Other populations were labeled in the diencephalon, including the supraoptic nucleus and nucleus ovalis; in the medulla the medial reticular area was labeled. Injections into the lateral hypothalamic area labeled neurons in the rostrolateral dorsal cortex, anterior, lateral, and dorsal septal nuclei, the striatoamygdalar area, nucleus accumbens, vertical limb of the diagonal band, nucleus of the accessory olfactory tract, the interstitial, ventral anterior, and ventral posterior amygdalar nuclei, several hypothalamic nuclei, and the posteroventral thalamic nucleus. Labeled brainstem populations included the ventral tegmental area, torus semicircularis, parvocellular and ventral isthmal nuclei, superior raphe, and the solitary nucleus. Injections in the dorsomedial hypothalamic nucleus labeled neurons in the rostral and caudolateral poles of the dorsal cortex, anterior septal nucleus, horizontal limb of the diagonal band, nucleus of the anterior commissure, several hypothalamic areas, the lateral habenula, the posteroventral thalamic nucleus, and cells scattered around the dorsolateral anterior thalamic nuclei. Labeled brainstem populations included the torus semicircularis, ventral tegmental area, superior raphe, parvocellular and ventral isthmal nuclei, and the lateral dorsal tegmental nucleus. The results of these studies are compared with findings in amphibians and mammals.

The limbic system of tetrapods: a comparative analysis of cortical and amygdalar populations.

Recent studies of the limbic system of tetrapods have made data available that challenge some of the long-held tenets of forebrain evolution. Using the basic principle of parsimony--that the best hypotheses concerning homologies are those requiring the fewest number of evolutionary changes--we have reevaluated comparisons of tetrapod limbic systems. Given the current data, the following points appear to be justified: (1) the common ancestors of reptiles and mammals had a well-developed limbic system in which the basic subdivisions and connections of the amygdalar nuclei were established; (2) the ventral part of the lateral pallium in amphibians appears to be a single structure which corresponds to at least four areas in reptiles: centromedial DVR, ventral anterior amygdala, lateral amygdala, and part of the lateral cortex; (3) the medial pallium in amphibians appears to be homologous with the dorsal and medial cortices in reptiles and with the general and hippocampal cortices in mammals: (4) the cortical targets of the main olfactory bulb in reptiles and mammals appear to be homologous, and their common ancestor probably had a corresponding olfactory pallial field; (5) the targets of the accessory olfactory bulb in amphibians, reptiles, and mammals appear to be homologous, with the exception of nucleus sphericus in reptiles, which lacks an obvious homologue in non-reptiles.

Factors affecting pharmacists' selection of rural or urban practice sites in Nebraska.

A questionnaire was used to determine why pharmacists in Nebraska chose urban or rural practice sites and to help the University of Nebraska College of Pharmacy encourage students to consider rural practice. Questionnaires were mailed to 1427 Nebraska pharmacists to gather data about their practice, job satisfaction, location of rearing, location of spouse's rearing, and prepharmacy and clerkship training. Usable responses were sorted into those from urban pharmacists (residing in Omaha and Lincoln and their suburban areas) and those from rural pharmacists (all others). Of the 689 usable responses, 315 (45.7%) were from urban pharmacists and 374 (54.3%) were from rural pharmacists. Of the rural pharmacists, 93% [corrected] grew up in communities of fewer than 100,000 people and 60% grew up in communities of fewer than 5,000 people. Respondents cited income potential, desirability of practice site, influence of spouse and family, and quality of children's schools as factors that most influenced their choice of practice site. Based on the survey results, the University of Nebraska College of Pharmacy took actions to recruit students from rural communities and increase students' exposure to rural practice settings. Pharmacists who were reared or trained in rural areas were more likely to practice in rural Nebraska than pharmacists who had only urban experience.

Auditory pathways to the hypothalamus in ranid frogs.

Three multisynaptic pathways from the midbrain auditory center (torus semicircularis) of the bullfrog, Rana catesbeiana, to the infundibular hypothalamus were found using the axonal tracer wheat germ agglutinin-horseradish peroxidase. Toral neurons project to the secondary visceral nucleus of the isthmus and to the central and anterior thalamic nuclei of the dorsal thalamus. All 3 of these nuclei project to the infundibular hypothalamus. These findings indicate multiple connections between two centers presumed important for reproductive behavior in frogs, a midbrain sensory region processing acoustic communication signals and a hypothalamic endocrine control area regulating gonadotropin and gonadal steroid secretion.

Anterior thalamic nucleus projections to the dorsal pallium in ranid frogs.

Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) applied in the anterior thalamic nucleus of ranid frogs was anterogradely transported to both the medial pallium and a ventral part of the dorsal pallium. Applications of WGA-HRP in the medial pallium labeled cells in the ipsilateral and contralateral anterior nucleus, including those considered to receive retinal input. An identical pattern of labeled cells was found in the anterior nucleus after WGA-HRP applications in the dorsal pallium. These results, combined with those of others, suggest that (1) the dorsal pallium has at least two subfields, (2) the dorsal pallium may receive a variety of non-olfactory sensory information, and (3) receipt of a disynaptic pathway from the retina may not determine isocortical homology among pallial fields in anurans.

Nuclear organization of the bullfrog diencephalon.

A cytoarchitectonic analysis was performed on the diencephalic nuclei of the bullfrog, Rana catesbeiana. The epithalamus contains two widely recognized habenular nuclei. The thalamus has three subdivisions: dorsal and ventral thalamus, and posterior tuberculum. The dorsal thalamus may be further parcelled into anterior, middle, and posterior zones. Connectional data from other studies support this zonation. The anterior zone projects to the telencephalic pallium. The middle zone nuclei receive a strong input from the midbrain roof and project to the telencephalic striatal complex. The posterior zone nuclei do not appear to project to the telencephalon; they may eventually be placed in the pretectum, a transitional area between the diencephalon and mesencephalon. Two of the ventral thalamic populations have been frequently placed in the dorsal thalamus and called the nucleus rotundus and the lateral geniculate nucleus. These terms imply homology with sauropsid dorsal thalamic nuclei, but our analysis and current connectional information do not support such homologies. We have given these populations more neutral names. The hypothalamus is divisible into a preoptic and infundibular hypothalamus, and the preoptic area can be further separated into anterior and posterior preoptic areas. The posterior area contains the magnocellular preoptic nucleus and a dorsal arm of this nucleus, often placed in the ventral thalamus, was recognized. We have tentatively placed the posterior entopeduncular nucleus in the hypothalamus.