M. Palkovits

Cholecystokinin innervation of the ventral striatum: A morphological and radioimmunological study

Immunocytochemistry, radioimmunological assay after surgical cuts, anterograde degeneration and retrograde tracing of fluorescent dyes were used in order to elucidate the cholecystokinin-containing afferents to the ventral striatum (nucleus accumbens, olfactory tubercle and ventral part of the caudate-putamen). In agreement with the report by Hökfelt et al., midbrain cholecystokinin-containing cells supply the posteromedial parts of the nucleus accumbens and olfactory tubercle, as well as the subcommissural part of caudate-putamen. Brainstem cholecystokinin afferents also reach more rostral parts of the ventral striatum including the rostrolateral olfactory tubercle. The ascending cholecystokinin axons enter the medial forebrain bundle at the meso-diencephalic border and maintain a rough medial to lateral topography at the caudal diencephalon. A second major cholecystokinin pathway, with possible origin in the piriform and medial prefrontal cortices and/or the amygdala, projects to the subcommissural caudate-putamen, the olfactory tubercle, the lateral part of the nucleus accumbens and the dorsal part of the bed nucleus of stria terminalis. Finally, the rostral part of the dorsal caudate-putamen receives a substantial cholecystokinin innervation from the basolateral amygdala and possibly from the neocortex. According to radioimmunological data, the descending telencephalic cholecystokinin system accounts for about 60% of all cholecystokinin in the rostral forebrain. The combined use of morphological and biochemical methods provided evidence for a partially overlapping distribution and possible interaction between an ascending brainstem and descending telencephalic cholecystokinin fiber systems within the striatum and related rostral forebrain areas.

Distribution of the pro-opiomelanocortin derived peptides, adrenocorticotrope hormone, α-melanocyte-stimulating hormone and β-endorphin (ACTH, α-MSH, β-END) in the rat hypothalamus

Abstract Rat hypothalamic nuclei were removed and assayed for adrenocorticotropic hormone (ACTH), β-endorphin (β-END) and α-melanocyte-stimulating hormone (α-MSH) content by radioimmunoassay, from the same samples. We also performed immunostaining for these 3 pro-opiomelanocortin (POMC) derived peptides on paraffin embedded serial sections of the hypothalamus. Areas known to project to the external zone of the median eminence receive a dense POMC innervation while those projecting to the posterior pituitary are not innervated. In addition, hypothalamic areas previously suggested to project to medullary autonomic centers are densely innervated. This innervation pattern may provide the morphological basis for the involvement of POMC peptides in neuroendocrine and autonomic functions. The biochemical data raise the possibility that the POMC precursor is processed differently in various brain regions.

Selective depletion of somatostatin in rat brain by cysteamine

Abstract A single injection of cysteamine (300 mg/kg, subcutaneously) results in a 70–80% decrease in somatostatin levels in the periventricular nucleus where somatostatin-producing neurons are located and the median eminence where somatostatinergic nerve terminals are. The drug seems quite selective: no changes in levels of other neuropeptides — LH-RH, vasopressin, enkephalin, VIP, CCK — were observed in the same animals.

Cholecystokinin in the nucleus of the solitary tract of the rat: evidence for its vagal origin

Nerve fibers and terminals immunoreactive for cholecystokinin (CCK) were demonstrated in the nucleus of the solitary tract (NTS) of the rat using light and electron microscopic immunocytochemistry. The following morphological and biochemical evidence suggests that CCK in the NTS seems to be of extrinsic, most probably vagal, origin: (1) axon fragments of the intracranial vagus were identified by immunostaining on their way to the solitary tract: (2) CCK-immunostaining could be localized in nerve terminals in the nucleus of the solitary tract, where only a very few immunopositive dendrites or cell bodies were present; and (3) transecting the major neuronal afferents (via solitary tract and/or more laterally) resulted in a complete disappearance of radioimmunoassayable CCK from the nucleus of the solitary tract.

Somatostatin connections between the hypothalamus and the limbic system of the rat brain

Somatostatin (SRIF) content of several brain structures was evaluated by radioimmunoassay in rats bearing various types of hypothalamic transections, as well as lesions of the amygdala. Analysis of the regional changes in SRIF concentrations after surgery suggest the following conclusions: (1) hypothalamic somatostatinergic neurons project to the limbic system, with the exception of the amygdaloid nuclei; (2) the olfactory tubercle, the lateral septal nucleus, the habenula and probably the hippocampus receive somatostatin projections from periventricular SRIF-containing cells; (3) somatostatin-containing fibers take a lateral course after leaving periventricular cells and join the medial forebrain bundle; (4) somatostatin innervation of the amygdala seems to be intrinsic.

Brainstem projection to the hypothalamic ventromedial nucleus in the rat: A CCK-containing long ascending pathway

In order to identify the source and topography of cholecystokinin-containing fibers innervating the hypothalamic ventromedial nucleus (VMN), radioimmunoassay, immunocytochemistry, retrograde tracing of horseradish peroxidase and anterograde degeneration techniques were used. Cholecystokinin (CCK) disappeared almost totally from the VMN following a caudal diencephalic knife cut, which transected the medial fibers of the internal capsule, and the dorsolateral portion of the medial forebrain bundle at the level of the mammillary body. A number of cells in the ipsilateral dorsal parabrachial nucleus, furthermore, showed intense CCK-like immunoreactivity. The ascending CCK-containing fibers in the lateral part of the medial forebrain bundle reach the VMN from the lateral side. Neither the fibers of the stria terminalis, nor of the medial corticohypothalamic tract seem to carry any significant amount of CCK to the VMN.

Somatostatin content of the hypothalamic ventromedial and arcuate nuclei and the circumventricular organs in the rat.

First Department of Anatomy, Semmelweis University Medical School, Budapest (Hungary), ( M.J.B., and J.S.K.) Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Md. 20014 and ( A. A,, H.S,, and A. V.S.) Endocrine and Polypeptide Laboratories, Veterans Administration Hospital and Department of Medicine, Tulane University School of Medicine, New Orleans, La. 70146 (U.S.A.)

On the origin of the serotonergic input to the intermediate lobe of the rat pituitary

Serotonin-containing nerve fibers have been visualized immunocytochemically in the intermediate lobe of the rat pituitary. A 50% depletion of the serotonin level in the intermediate lobe was obtained in our previous experiment in rats with pituitary stalk transection, which may represent the total neuronally derived serotonin there. In the present studies we have attempted to determine the source of these fibers by examining the effect of hypothalamic and midbrain lesions or fiber transections on serotonin levels and serotonin-containing neuronal elements. Complete hypothalamic deafferentation resulted in a significant reduction of immunostained fibers in the intermediate lobe. A 27% fall in the serotonin content (measured by HPLC and electrochemical detection) and a significant disappearance of immunostained fibers were observed after transecting the ascending fibers from the raphe nuclei towards the hypothalamus. The transection combined with the lesioning of the hypothalamic dorsomedial nuclei resulted in a 50% decrease of serotonin level in the intermediate lobe. The present data therefore suggest that serotonin fibers in the intermediate lobe may originate from cells both in the midbrain raphe and hypothalamic dorsomedial nuclei.

Distribution of immunoreactive dynorphin A1–8 in discrete nuclei of the rat brain: Comparison with dynorphin A

The distribution of immunoreactive (ir)-dynorphin A1-8 (Dyn A1-8) in 78 microdissected rat brain areas as well as in the neurointermediate lobe of pituitary gland was determined using a highly specific radioimmunoassay. The highest concentrations of Dyn A1-8 in brain were found in substantia nigra (673.8 fmol/mg protein) and lateral preoptic area (565.1 fmol/mg protein). High concentrations of ir-Dyn A1-8 (greater than 240 fmol/mg protein) were found in 5 nuclei: ventral premamillary nucleus, anterior hypothalamic nucleus, dorsomedial nucleus, arcuate nucleus, and medullary reticular nuclei. Moderate concentrations of the peptide (between 120 and 240 fmol/mg protein) were found in 55 brain nuclei such as septal and amygdaloid nuclei, most diencephalic structures, mesencephalic nuclei, pons and medulla oblongata nuclei and others. Low concentrations of ir-Dyn A1-8 (less than 120 fmol/mg protein) were found in 16 regions, e.g. frontal cortex, hippocampus, caudate-putamen cortical amygdaloid nucleus, several thalamic nuclei, mamillary body superior and inferior colliculi, cerebellar nuclei and others. The posterior thalamic nucleus has the lowest ir-Dyn A1-8 concentration (62.0 fmol/mg protein). The neurointermediate lobe of the pituitary gland is extremely rich in ir-Dyn A1-8 (4063.0 fmol/mg protein).

Quantitative histological studies on the hypothalamic paraventricular nucleus in rats. II. Number of local and certain afferent nerve terminals

The total number and the numerical ratio of extrinsic and intrinsic (local) innervations of magnocellular neurons in the paraventricular nucleus (mPVN) were determined after surgical isolation of the nucleus in rats. Various lesions and transections of fibers running to the mPVN were performed to determine the number and possible sources of septal, hippocampal and caudal periventricular fibers to the mPVN. The relatively high proportion of possibly intrinsic connections (43%) suggests a local, integrative function of neuronal activity in the PVN. On the average, 57% of the total number of presynaptic boutons have been found to originate from outside the nucleus (extrinsic afferentation). Only 7% of these fibers ascend from caudal through the periventricular area. mPVN afferents originating from the ventral subiculum and from the lateral septal nucleus comprise about 3 and 5% of the extrinsic afferentation, respectively.