Effects of colchicine on axonal transport and ultrastructure of the hypothalamo-neurohypophyseal system of the rat

Anatomical and functional implications of corticotrophin-releasing hormone neurones in a septal nucleus of the avian brain: an emphasis on glial-neuronal interaction via V1a receptors in vitro

Previously, we showed that corticotrophin-releasing hormone immunoreactive (CRH-IR) neurones in a septal structure are associated with stress and the hypothalamic-pituitary-adrenal axis in birds. In the present study, we focused upon CRH-IR neurones located within the septal structure called the nucleus of the hippocampal commissure (NHpC). Immunocytochemical and gene expression analyses were used to identify the anatomical and functional characteristics of cells within the NHpC. A comparative morphometry analysis showed that CRH-IR neurones in the NHpC were significantly larger than CRH-IR parvocellular neurones in the paraventricular nucleus of the hypothalamus (PVN) and lateral bed nucleus of the stria terminalis. Furthermore, these large neurones in the NHpC usually have more than two processes, showing characteristics of multipolar neurones. Utilisation of an organotypic slice culture method enabled testing of how CRH-IR neurones could be regulated within the NHpC. Similar to the PVN, CRH mRNA levels in the NHpC were increased following forskolin treatment. However, dexamethasone decreased forskolin-induced CRH gene expression only in the PVN and not in the NHpC, indicating differential inhibitory mechanisms in the PVN and the NHpC of the avian brain. Moreover, immunocytochemical evidence also showed that CRH-IR neurones reside in the NHpC along with the vasotocinergic system, comprising arginine vasotocin (AVT) nerve terminals and immunoreactive vasotocin V1a receptors (V1aR) in glia. Hence, we hypothesised that AVT acts as a neuromodulator within the NHpC to modulate activity of CRH neurones via glial V1aR. Gene expression analysis of cultured slices revealed that AVT treatment increased CRH mRNA levels, whereas a combination of AVT and a V1aR antagonist treatment decreased CRH mRNA expression. Furthermore, an attempt to identify an intercellular mechanism in glial-neuronal communication in the NHpC revealed that brain-derived neurotrophic factor (BDNF) and its receptor (TrkB) could be involved in the signalling mechanism. Immunocytochemical results further showed that both BDNF and TrkB receptors were found in glia of the NHpC. Interestingly, in cultured brain slices containing the NHpC, the use of a selective TrkB antagonist decreased the AVT-induced increase in CRH gene expression levels. The results from the present study collectively suggest that CRH neuronal activity is modulated by AVT via V1aR involving BDNF and TrkB glia in the NHpC.

Inter- and intra-nuclear differences in galanin expression between the hypothalamic paraventricular and supraoptic nuclei in colchicine-untreated rats

Not much is known of the topography of galanin expression in the hypothalamic supraoptic (SON) and paraventricular (PVN) nuclei neurons in colchicine (an axoplasmic inhibitor)-untreated animals. Insight into the biological implication(s) of galanin expression in the PVN and SON will depend, at least in part, on the nature of its distribution in colchicine-untreated animals. In this study therefore, the topographical distribution of galaninergic profiles was examined in the PVN and SON of colchicine-untreated rats. Staining in the parvocellular PVN (PVN(p)) was predominantly as varicose thin galanin fiber processes while the magnocellular PVN (PVN(m)) contained large cell soma and fiber processes. The relative fiber density was higher in the anterior, periventricular and medial PVN(p) than in the dorsal, lateral and posterior subdivisions. Large-sized cells and thick fibers were limited to the posterior PVN(m) while the anterior and medial PVN(m) contained varicose profiles. Light- and intensely-stained galanin-positive cells as well as large- and small-diameter (varicose or non-varicose) fibers were observed in the SON. The large and thin fibers exhibit preferential ventral and dorsal distribution, respectively. Together with the complexity of specific afferent and efferent connections within the PVN and SON, these observations underscore heterogeneous galanin expression and raise potential implications for understanding the biological role of galanin by physiologically challenging stimuli.

Potential strategies for ameliorating early cancer anorexia

BACKGROUND

Normally the lateral hypothalamic area (LHA) and the ventromedial nucleus (VMN) interact to regulate food intake (FI), the product of meal number (MN) and meal size (MZ), by changes in neurotransmitters, mainly dopamine and serotonin. Change in LHA dopamine influences meal size; while in VMN, decreasing dopamine and increasing serotonin levels influence meal number. Whether this situation exists in early cancer anorexia was tested in a series of studies to examine the role of the hypothalamus in the pathogenesis of early cancer anorexia.

MATERIALS AND METHODS

In experiment 1, male Fischer tumor-bearing (TB) rats and weight-matched controls had FI, MN, and MZ measured continuously via a computerized rat eater meter. At onset of anorexia, feeding patterns were measured. In experiment 2, the VMN was temporarily blocked with 0.32 microgram of colchicine in TB rats, while TB controls had an equal volume of intra-VMN saline, and changes in feeding patterns were measured. In experiment 3, changes in VMN dopamine and serotonin were measured via microdialysis at anorexia and after tumor resection.

RESULTS

In experiment 1, with the onset of anorexia, food intake decreased significantly in TB rats, initially by a decrease in MN and then by a decrease in both MN and MZ. No change occurred in controls, suggesting that VMN versus LHA played a more significant role in mediation of cancer anorexia. In experiment 2, following VMN block, FI increased significantly in anorectic TB rats, achieved by an almost exclusive increase in MN with minimal change in MZ, thus supporting the role of the VMN in anorexia. In experiment 3, at the onset of anorexia, FI decreased significantly in TB rats versus controls. TB rats had a significant increase in VMN serotonin and a significant decrease in VMN dopamine. After tumor resection, food intake improved and high levels of serotonin normalized with no change in dopamine.

CONCLUSION

Serotoninergic and dopaminergic systems are involved in the etiology of cancer anorexia. The changes in food intake are mediated via the VMN by a decrease in meal number.

Multiple peptides infrequently coexist in progesterone receptor-containing neurons in the ventrolateral hypothalamic nucleus of the guinea-pig: an immunocytochemical triple-label analysis of somatostatin, neurotensin and substance P

Progesterone plays an important role in regulating reproductive behaviour in guinea-pigs through actions exerted at the ventrolateral nucleus (VL), an area of the brain that contains progesterone receptors (PR) and neuroactive peptides, somatostatin (SOM), neurotensin (NT) and substance P (SP). Previous double-label analyses provided evidence that a substantial proportion of these neuropeptidergic cells contain PR. By means of triple-label immunofluorescence histochemistry, we examined whether PR are colocalized with two neuropeptides (SOM + NT or SP + SOM or SP + NT) within the same neurons in the VL. Ovariectomized guinea-pigs were primed with estradiol to induce PR immunoreactivity, and treated with colchicine to visualize immunoreactive (IR) neuropeptidergic cells. Both monoclonal mouse PR and polyclonal rabbit neuropeptide antibodies were used in double staining and in elution-restaining experiments. In the whole VL, the proportion of each coexisting peptide with PR obtained after double immunofluorescence appeared in decreasing order as: SOM (34%)>NT (25%)>SP (20%). Occasional colocalization was seen between PR and two neuropeptides throughout the rostrocaudal extent of the VL. Combining our various quantitative observations, we found that, of the total population of PR-IR neurons containing any combination of SOM, NT and SP, only about 1.5% contained SOM and NT, 2% contained SP and SOM and 1.6% contained SP and NT. These results indicate that while many PR-IR neurons also contain SOM or NT or SP in the guinea-pig VL, there may be very few PR-IR neurons that express more than one of these three peptides.

Chromatographic analysis of the enkephalin immunoreactivity in the nucleus locus coeruleus of the cat after local colchicine administration

Cell bodies immunoreactive for methionine- and leucine-enkephalin are found in the area of the locus coeruleus (dorsolateral pons) of the cat after injection of colchicine in the ascending projections of the nucleus. Using radioimmunoassay procedures, it is shown that colchicine induces a significant increase in methionine- and leucine-enkephalin-immunoreactive material in this area of the brain. High pressure liquid chromatography analysis demonstrated that the immunoreactive materials were authentic methionine- and leucine-enkephalin. The methionine- and leucine-enkephalin patterns were identical in the colchicine injected and non-injected sides of the dorsolateral pons. It is suggested that, in this area of the brain, colchicine (i) does not significantly modify the processing of proenkephalin to form the pentapeptides methionine- and leucine-enkephalin, and (ii) does not induce the appearance of new substances reactive to the enkephalin antisera employed.

Colchicine-induced accumulation of estrogen receptor and progestin receptor immunoreactivity in atypical areas in guinea-pig brain

Using immunocytochemical techniques, cells containing estrogen and progestin receptors have been observed in many discrete regions of the guinea-pig forebrain, including the mediobasal hypothalamus and preoptic area. While most reaction product is located within cell nuclei, we have reported abundant reaction product in perikaryal cytoplasm and neuronal processes as well. Ultrastructural analysis has revealed the presence of estrogen and progestin receptors in atypical subcellular sites within the hypothalamus, including dendrites and axon terminals. In order to determine if microtubule-dependent intracellular transport is involved in intraneuronal transport of steroid hormone receptors, ovariectomized guinea-pigs were injected intracerebroventricularly with the microtubule inhibitor, colchicine, and brain sections at the level of the hypothalamus were immunostained for estrogen receptors. This treatment resulted in the appearance of estrogen receptor immunoreactivity in the paraventricular and mediodorsal thalamic region, areas typically devoid of estrogen receptor-immunoreactive cells in guinea-pigs. In a second study on progestin receptors, we observed the colchicine-induced accumulation of progestin receptor immunoreactivity in the paraventricular thalamic, mediodorsal thalamic and lateral dorsal thalamic areas as well as in the medial amygdala, all areas typically devoid of progestin receptor immunoreactivity. While estradiol injection induced progestin receptor immunoreactivity in the hypothalamus and preoptic area as described previously, it had no effect on the colchicine-induced accumulation in the thalamus and amygdala. These results provide evidence that in some neurons, progestin receptors and estrogen receptors are transported intracellularly, apparently at a rapid enough rate that they do not ordinarily accumulate within the perikaryon.

Similarities in the ultrastructural distribution of nerve growth factor receptor-like immunoreactivity in cerebellar Purkinje cells of the neonatal and colchicine-treated adult rat

The intracellular distribution of nerve growth factor receptor immunoreactivity was examined by electron microscopy in the cerebellum of adult and postnatal day 12 rats. The very faint immunostaining in Purkinje cells of naive adult animals was greatly amplified after colchicine treatment. Neonatal cerebellum, in contrast, contained prominent immunoreactivity in both Purkinje cells and germinal cells of the external granular layer. Intracellular distribution of the nerve growth factor receptor reaction product was very similar in Purkinje cells of both neonatal and colchicine-treated adult animals. It was consistently present along the perikaryal cell membrane, in segments of the rough endoplasmic reticulum and Golgi complex. Numerous membrane-bound aggregates of immunoreactive vesicles resembling multivesicular bodies (secondary lysosomes) were scattered throughout the cell soma, although less frequently in neonatal rats. Bulbous expansions along the proximal axons of colchicine-treated Purkinje cells were filled with such immunoreactive multivesicular bodies. These cells also displayed evidence of nerve growth factor receptor internalization in the form of immunoreactive coated vesicles situated near the cell membrane. In addition to the staining in Purkinje cells, neonatal cerebellum contained high amounts of nerve growth factor receptor reaction product along the cell membrane of germinal cells in the external granular layer. Although Purkinje cells of naive adult animals possessed little or no cell membrane-related nerve growth factor receptor immunoreactivity, reaction product was sometimes seen in cisternae of the rough endoplasmic reticulum and Golgi apparatus. These findings provide electron microscopic immunocytochemical evidence of nerve growth factor receptor synthesis, internalization, and catabolism in noncholinergic neurons of the central nervous system.

Hypothalamic galanin-immunoreactive neurons projecting to the posterior lobe of the rat pituitary: a combined retrograde tracing and immunohistochemical study

To identify the galanin-immunoreactive neurons projecting to the posterior lobe of the pituitary in the rat hypothalamus, a retrograde tracer (complex of wheat germ agglutinin-enzymatically inactive horseradish peroxidase-colloidal gold) was injected into the posterior lobe of the pituitary. Sections of the hypothalamus were treated with a combination of silver enhancement of retrogradely transported tracer and immunohistochemistry of galanin. Of the total number of hypothalamic cells doubly labeled with retrograde tracing and galanin-immunostaining, 56-60% were found in the supraoptic nucleus, 18-23% in the retrochiasmatic nucleus, 8-10% in the lateral magnocellular portion of the paraventricular nucleus. The ratio of (number of doubly labeled cells/number of galanin-immunoreactive cells) in each of the above regions was similar to the ratio of (number of retrogradely labeled cells/number of Nissl-stained cells) in the supraoptic nucleus. Of all retrogradely labeled cells in the hypothalamus, 51-56% also contained galaninlike immunoreactivity.

IN CONCLUSION

(1) galanin-immunoreactive fibers in the posterior lobe of the pituitary originate mainly in the supraoptic nucleus, retrochiasmatic nucleus, and lateral magnocellular portion of the paraventricular nucleus, (2) most of galanin-immunoreactive cells in these regions project to the posterior lobe of the pituitary, and (3) about half the neurons constituting the hypothalamo-neurohypophyseal system contain galaninlike immunoreactivity.

Comparison of the neurotoxic effects of colchicine, the vinca alkaloids, and other microtubule poisons

Previous studies have revealed that colchicine is selectively toxic to certain neuronal populations in the CNS, particularly granule cells of the dentate gyrus. The present study evaluates whether other microtubule poisons exhibit similar neurotoxic effects. Equimolar solutions of colchicine, colcemid, podophyllotoxin, vinblastine, vincristine and lumicolchine, the non-binding analog of colchicine, were injected into the dentate gyrus. Neurotoxicity was evaluated histologically. As previously reported, colchicine selectively destroyed dentate granule cells with minimal damage to other neurons including hippocampal pyramidal cells. Vincristine was very toxic and was not selective for granule cells. Vinblastine was relatively selective in destroying granule cells, but was not as potent as colchine. Colcemid and podophyllotoxin had minimal toxic effects. Lumicolchine injections caused no more damage than injections of vehicle. This ordering appears to correlate with the reversibility of binding tubulin.

Comparative distribution of three opioid systems in the lower brainstem of the monkey (Macaca fuscata)

The regional distribution of the three opioid peptide neuronal systems--proopiomelanocortin (POMC), proenkephalin A, and proenkephalin B--was investigated in the lower brainstem of Japanese monkeys (Macaca fuscata) by immunocytochemical techniques. Antiserum to beta-endorphin/beta-lipotropin, [Met]-enkephalin-Arg6-Gly7-Leu8, and human leumorphin were used to identify the POMC and the proenkephalin A and B systems, respectively. POMC-related immunoreactive material was not found in the neuronal perikarya in the lower brainstem; reactive fibers and apparent terminals were distributed in the substantia nigra, lemniscus lateralis, midbrain central gray, the nucleus raphes, nucleus parabrachialis lateralis, ventral area of the spinal trigeminal nerve, nucleus tractus solitarii, and in the reticular formation throughout the lower brainstem. Proenkephalin A-related immunoreactive neuronal perikarya were detected in the central gray, reticular formation, nucleus raphes, trapezoid body, nucleus parabrachialis lateralis and medialis, nucleus spinalis nervi trigemini, nucleus dorsalis nervi vagi, and in the nucleus tractus solitarii. Densely packed immunoreactive fibers were widely distributed in the substantia nigra, nucleus interpeduncularis, nucleus raphes, superior colliculus, periaqueductal central gray, nucleus parabrachialis lateralis and medialis, locus coeruleus, trapezoid body, nuclei cochleares, nucleus spinalis nervi trigemini, tractus spinalis nervi trigemini, nucleus tractus solitarii, nucleus dorsalis nervi vagi, nucleus gracilis, nucleus cuneatus, nucleus cuneatus accessorius, and in the reticular formation throughout the lower brainstem. Neuronal perikarya containing immunoreactive material related to proenkephalin B were found in the periaqueductal central gray, nucleus parabrachialis lateralis and medialis, nucleus tractus solitarii, and nucleus spinalis nervi trigemini. In addition, immunoreactive fibers were detected in the ventral tegmental area, substantia nigra, nucleus parabrachialis lateralis and medialis, nucleus vestibularis lateralis and medialis, and in some areas of the reticular formation. These anatomical findings demonstrate that these three opioid peptide neuronal systems are widely but uniquely distributed in the lower brainstem of the monkey.

Selective axonal transport in a single cholinergic axon of Aplysia--role of colchicine-resistant microtubules

Substance-specific selective axonal transport was examined in a single axon by injecting [3H]leucine and [14C]acetylcholine simultaneously into the cell body of a giant cholinergic neuron (R2) in the abdominal ganglion of Aplysia kurodai. The ganglion and attached nerves were cultured for several hours after the injection and the migration of radioactive substances along the axons of the injected neuron was examined. The substances examined were 3H labeled membrane proteins and soluble proteins synthesized in the cell body, 14C labeled bound acetylcholine formed in the cell, injected [3H]leucine and soluble [14C]acetylcholine. Membrane proteins and bound acetylcholine (plus a part of soluble acetylcholine) moved along the axon somatofugally at maximum velocities of 2.4 and 1.7 mm/h, respectively, at 25 degrees C. Soluble proteins, free leucine and most of the soluble acetylcholine did not move by fast axonal transport but diffused inside the axon of the neuron R2 at rates predicted from their expected diffusion constants in the axoplasm [Koike H. and Nagata Y. (1979) J. Physiol. 295, 397-417]. The diffusion kinetics of these substances were analysed and used for determination of true axon length, and to separate axonal transport components from diffusing components. An antimitotic drug, colchicine, selectively suppressed the axonal transport of membrane proteins but not of acetylcholine at 1-5 mM concentration, though it finally blocked the axonal transport of acetylcholine at 20 mM. When 1-5 mM colchicine was separately perfused only to the distal axon of the neuron R2, the migration of membrane proteins was stopped just proximal to the colchicine perfusion zone but acetylcholine migration was not disturbed by the drug. The moving component of acetylcholine was recovered by sucrose density centrifugation from a compartment previously reported as that of vesicular acetylcholine. As a possible mechanism of this selective axonal transport, it is proposed that there are two groups of microtubules: a colchicine-sensitive group of microtubules which may transport membrane proteins, and a colchicine-resistant group which may preferentially transport the transmitter substance acetylcholine at a slower rate.

Effect of colchicine on micturition reflex in rats

Intracerebral or intraspinal cord, but not intraperitoneal, injection of low doses of colchicine in rats induces specific toxic symptoms. This paper deals in particular with the effect of colchicine on micturition. After the injection of 5-25 micrograms/rat in cerebral ventricle or 2.5-20 micrograms/rat intraspinal cord, bladder content was markedly increased, due to a dramatic urine retention. Time of latency of vesical retention was related to the dose and to the route of colchicine administration. Cystometrographic analyses were performed in control and treated rats at various intervals of time after the injection: bladder tone, as expressed by the delta P/delta V ratio, monitored from 12 to 120 hr after colchicine injection, decreased more and more during time, suggesting that the observed vesical hypotonicity is an irreversible phenomenon.

Effects of colchicine on the intraneuronal transport of secretory material prior to the axon: a morphofunctional study in hypothalamic neurosecretory neurons of the rat

The effects of colchicine on neurosecretory neurons of the rat hypothalamus were studied by immunocytochemistry, high-resolution radioautography, and conventional electron microscopy. In control rats, intraneuronal immunocytochemical labeling of vasopressin, oxytocin and somatostatin occurred essentially in the Golgi apparatus, the neurosecretory granules and to a lesser extent, the endoplasmic reticulum. These immunostaining patterns were dramatically modified 24 h after the administration of colchicine: immunoreactive peptides were located in granular or tubular structures accumulated at the periphery of the perikarya, but the Golgi stacks were not immunostained. Two h after the administration of tritiated leucine, quantitative analysis of radioautographic labeling of supraoptic perikarya revealed large amounts of radioactive protein in the Golgi saccules of neurosecretory neurons in control rats, but in the neurons of colchicine-treated rats, radioautographic labeling was mainly located in granular structures accumulated at the periphery of the perikarya, with no significant labeling on the Golgi stacks. Lastly, 3 noteworthy effects of colchicine on the ultrastructural morphological features of these neurosecretory neurons consisted in: (1) a dramatic disorganization of the Golgi complexes, (2) an accumulation of electron-dense proteic material within the lumen of cisternae of both the rough and smooth endoplasmic reticulum and, (3) a marked depolymerization of perikaryal microtubules, specifically those associated with the Golgi stacks. Taken together, these data do not fit the prevailing concept that the colchicine-induced accumulation of secretory material within the perikarya of neurosecretory neurons essentially results from the blockade of axoplasmic transport mechanisms. Instead, they support the idea that the effects of colchicine are related to the inhibition of the intraneuronal transport of newly synthesized secretory material from the endoplasmic reticulum to the Golgi apparatus, suggesting that the microtubules associated with the Golgi stacks are possible sites of colchicine action.

Immunocytochemical ultrastructural study of hypothalamic neurons containing corticotropin-releasing factor in normal and adrenalectomized rats

The neurons of the rat hypothalamus which secrete corticotropin-releasing factor were studied by using a pre-embedding immunocytochemical staining technique that improves both the penetration of immunoreagents within the tissue and the preservation of the ultrastructural morphology of labeled structures. Comparison was made between the subcellular location of corticotropin-releasing factor-41 in perikarya of the paraventricular nucleus and axons of the median eminence, both in intact and adrenalectomized animals either untreated or 24 h after the intracerebral injection of colchicine. Morphometric analysis of the numerical density and of the diameter of corticotropin-releasing factor immunoreactive neurosecretory granules in axons of the median eminence of rats not treated with colchicine, indicated that the main modifications induced by adrenalectomy concerned (1) the differential repartition of labeled granules within the preterminal and terminal axonal portions of the median eminence, and (2) the enlargement of the diameter of labeled granules contained in these axons (from 98 nm to 165 nm). In the hypothalamus of intact and adrenalectomized rats, colchicine treatment increased the number of corticotropin-releasing factor-immunoreactive granules in the neuronal perikarya and reduced their number in the axons, but both these variations were much more marked in adrenalectomized rats. Although the corticotropin-releasing factor immunoreactive granules that accumulated in the perikarya after colchicine treatment were slightly smaller than those in the corresponding axons, the diameter of perikaryal-labeled granules was larger in adrenalectomized than in intact animals (129 nm vs 93 nm). These findings fit the idea that adrenalectomy markedly stimulates both the synthesis and axonal excretion of secretory granules in the hypothalamic neurons secreting corticotropin-releasing factor. They also indicate that suppression of circulating corticosteroids induces qualitative modifications in these neurons leading to the visualization of larger neurosecretory granules, which may reflect differential synthesis and granular packing of synergistic peptides other than corticotropin-releasing factor and/or changes in the process of intragranular maturation of hormonal material.

Neuropeptide Y-like immunoreactivity in cat spinal cord with special reference to autonomic areas

The distribution of nerve terminal-like structures (herein called nerve terminals), fibers, and neurons containing neuropeptide Y-like immunoreactivity (NPY-ir) was studied immunohistochemically in cat spinal cord with and without colchicine treatment. Rexed laminae II and III of the dorsal horn contained large amounts of immunoreactive nerve terminals and few fibers at all levels of the cord whereas laminae I and IV-VI contained fewer terminals and numerous fibers. In segments C7-T3, fibers with NPY-ir in the superficial laminae collected into bundles which travelled ventromedially toward the dorsal gray commissure (DGC). In addition, another bundle of fibers was present in segments C8-T2 and T11-S2; these fibers also originated from the upper dorsal laminae and travelled along the dorsomedial border of the gray matter to cross the midline in the DGC. In the intermediate and central gray, most immunoreactivity was found in the autonomic areas: terminals and fibers containing NPY-ir were found in the intermediolateral cell column pars principalis (IMLp) in all segments between C8 and L4 with the densest accumulation in segments T6 and T7. All other autonomic areas contained immunoreactive structures in nearly all thoracolumbar segments except for the IML pars funicularis, which contained small numbers of immunoreactive fibers only between segments T2 and T8, inclusive. In the sacral cord, the autonomic areas in the intermediate and central gray also contained relatively large numbers of immunoreactive terminals and fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of substance P-like immunoreactivity in Xenopus embryos

The development of substance P-like immunoreactivity (SPLI) was studied in the Xenopus embryonic nervous system in order to determine in which neuronal populations and at what developmental times SPLI is expressed. Although Rohon-Beard neurons initially were thought to be the only substance P-immunoreactive cells in the embryonic frog spinal cord, we have demonstrated that several neuronal phenotypes are immunoreactive. The earliest evidence of SPLI was seen at stage 28 (Nieuwkoop and Faber, '67), at which time only some trigeminal ganglion cells, their axons in the ophthalmic nerve, and axons in the lateral tracts of the hindbrain showed SPLI. In the embryonic brain at stages 29/30, 37/38, and 42, SPLI was seen in the hypothalamus, trigeminal ganglion cells and their peripheral axons, the sensory roots of cranial nerve IX/X, and axons in the hindbrain lateral tracts. At premetamorphic stages, SPLI was found in several populations that are immunoreactive in adult amphibia. In the embryonic spinal cord, Rohon-Beard neurons were labeled consistently with reaction product; there was a rostrocaudal time gradient of immunoreactivity with increasing development. The Rohon-Beard neurons were not immunoreactive at developmental stages in which axonal outgrowth was beginning (stage 21), but were strongly immunoreactive at stages in which target cells had been contacted (stage 29). Several types of interneurons in the spinal cord (as classified by Roberts and Clarke, '82) showed SPLI during embryonic stages. At premetamorphic stages the Rohon-Beard neurons began to disappear and the immunoreactive interneurons were distributed similarly to those reported in the adult. Dorsal root ganglia differentiated during these stages, and at this time some of the neurons belonging to these ganglia exhibited substance P-like immunoreactivity.

Immunocytochemical evidence for stimulatory control by the ventral noradrenergic bundle of parvocellular neurons of the paraventricular nucleus secreting corticotropin releasing hormone and vasopressin in rats

The regulation, by catecholaminergic innervation, of parvocellular neurons of the paraventricular nuclei (PVN) secreting corticotropin releasing hormone (CRH) and vasopressin (Vp) was studied by immunocytochemical visualization of both neurohormones in control rats and in rats given discrete injections of 6-hydroxydopamine in the ventral noradrenergic ascending bundle (VNAB). In both groups, the changes in immunostaining intensities observed in axon terminals of the external median eminence and in PVN perikarya 48 h after a blockade of axoplasmic transport by intraventricular injections of colchicine, served as an index for hormonal release and synthesis. In controls, this treatment induced a strong decrease in CRH and Vp immunoreactivity within the terminals, together with intense labeling of PVN perikarya containing CRH. By contrast, bilateral VNAB lesions strikingly inhibited both the colchicine-induced reduction of the CRH and Vp immunoreactivity in axons and the accumulation of CRH in the perikarya. Unilateral VNAB lesions induced similar alterations but these were restricted to the ipsilateral PVN and median eminence. Comparison of these immunocytochemical data with earlier physiological observations on the effects of VNAB lesions on ACTH secretion indicates that the catecholaminergic afferents to the PVN conveyed by the VNAB stimulate the release and the synthesis of CRH and Vp by parvocellular neurons projecting into the external median eminence.

Segmental distribution of corticotropin-releasing factor-like and vasoactive intestinal peptide-like immunoreactivities in presumptive sympathetic preganglionic neurons of the cat

The distribution of corticotropin-releasing factor (CRF), vasoactive intestinal peptide (VIP), and luteinizing hormone-releasing hormone (LH-RH) in cell bodies of sympathetic autonomic nuclei of the thoracolumbar spinal cord was studied immunohistochemically in cats after intrathecal administration of colchicine. Neurons containing CRF-like immunoreactivity (CRFir) and VIP-like immunoreactivity (VIPir), but not LH-RH-like immunoreactivity, were found in the intermediolateral nucleus pars principalis (IMLp) and pars funicularis (IMLf). On the basis of identification in previous studies and the size, shape, and location of the immunoreactive cells, it is suggested that the neurons are sympathetic preganglionic neurons. Most of the neurons with CRFir (85.5%) were found in the IMLp in segments T2-T7 and L2-L3 and the remaining 14.5% were found in the IMLf in segments T2-T5. The largest proportion of neurons with VIPir (93.7%) was found in the IMLp in segments T2, T4-T7, and T9-T13. Only 6.3% of the neurons containing VIPir were found in the IMLf in segments T2, T4, T5, and T10. These findings suggest that CRF and VIP may participate in peptide-specific pathways to peripheral organs.

Somatostatin-like immunoreactivity in neurons, nerve terminals, and fibers of the cat spinal cord

The distribution of somatostatin-like immunoreactivity (SS) was studied in the spinal cord of untreated cats and of cats that had received colchicine at all levels of the cord. In the dorsal horn small (less than 15 microns in diameter), round neurons were found in Rexed laminae II and III at all levels. At all levels laminae IV-VI contained smaller numbers of immunoreactive neurons that were medium (between 15 and 25 microns in diameter) to large (greater than 25 microns in diameter) in size. In addition, small numbers of medium-sized neurons were observed at the dorsal and dorsomedial borders of the gray and white matter in segments C1-5. In the sacral cord (S1-3), a group of medium-sized bipolar neurons was found in the dorsolateral funiculus. In transverse sections the processes of the neurons in these two latter groups travelled in a direction parallel to the border of the gray and white matter. In the intermediate and central gray matter, in addition to the immunoreactive neurons found in the region of the intermediolateral nucleus and nucleus intercalatus of lamina VII in segments C8 to L4 (Krukoff et al., '85a), lamina VII contained immunoreactive neurons at all levels with the largest number occurring in the thoracic cord. These neurons were medium to large in size and were generally multipolar with processes travelling in all directions. Multipolar small immunoreactive neurons were also found in the central gray region (lamina X) in the thoracic and upper lumbar cord. Finally, small numbers of neurons containing SS were found in the ventral horn of the cervical and upper thoracic cord. These multipolar neurons were medium to large in size. The distribution of nerve terminals and fibers containing SS was similar to that previously described in mice, rats, guinea pigs, and primates. Although the function of somatostatin in the spinal cord is not known, its presence in neurons with short processes suggests that it may act to modify local activity in the regions where it is found, including areas involved in sensory, visceromotor, and motor functions.

Segmental distribution of peptide-like immunoreactivity in cell bodies of the thoracolumbar sympathetic nuclei of the cat

The distribution of leucine-enkephalin, methionine-enkephalin, neurotensin, somatostatin, substance P, oxytocin, vasopressin, and neurophysin II in cell bodies of sympathetic autonomic nuclei of the thoracolumbar (T-L) spinal cord was studied immunohistochemically in cats after intrathecal administration of colchicine. Neurons containing only enkephalin-, neurotensin-, somatostatin-, and substance P-like immunoreactivity (ENK, NT, SS, SP, respectively) were found in the intermediolateral nucleus pars principalis (IMLp) and pars funicularis (IMLf), the nucleus intercalatus (IC), and the central autonomic area (CA). The size, shape, location, and numbers of the peptide-positive neurons in the IMLp, IMLf, and IC suggested that they were sympathetic preganglionic neurons (SPN). This was confirmed by a combined retrograde tracing/immunohistochemical study showing that most of these neurons at the levels of the T-L cord known to provide preganglionic fibers to the stellate ganglion were SPN. On the other hand, the functional identification of the neurons in the CA is uncertain as neurons were not observed which were both retrogradely labelled and contained ENK, NT, SS, or SP. Immunoreactive neurons in each area were counted in ten sections from each segment from C8 to L4. In the IMLp, the SPN with ENK were greatest in number (up to 25) in segments T4-T7 and L2-L3. The maximum number of SPN containing NT was found in segments T4-T7 (45 neurons). Of the four peptides, neurons containing SS were found in the greatest number (up to 48 in segments T2-T6); neurons containing SP were found in the smallest number (15 or fewer per segment). Few SPN containing each of the four peptides were found in the IC; CA neurons with ENK and NT were also few in number. A comparison of the numbers of immunoreactive neurons in the IML with earlier estimates for the total numbers of SPN in the IML at each level showed that the proportions of IML neurons containing each of the four peptides were fairly consistent throughout the T-L cord, with some exceptions. These results suggest that the innervation of visceral organs is not obviously peptide-specific, although some organs may be innervated by a greater proportion of SPN containing one of these peptides. Finally, the presence of ENK, NT, SS, and SP in SPN suggests that these four peptides act as neurotransmitters in preganglionic pathways to sympathetic ganglia.

The effects of colchicine in mammalian brain from rodents to rhesus monkeys

The injection of colchicine into rats and monkeys produced two different types of brain damage. At selected doses, intradentate colchicine preferentially destroyed DGC in rats, whereas damage was less selective and more severe in monkeys. Experiments were performed with different tubulin-binding drugs to investigate the structure-function relationship of tubulin binding and DGC death. The tubulin-binding characteristics of these and other drugs reported in the literature did not correlate with their ability to damage DGC. The role of seizure-induced cell death was investigated by recording the EEG in monkeys and in rats treated with phenobarbital. The data suggest that seizures are an infrequent epiphenomenon of colchicine's action. We proposed that colchicine is not a selective neurotoxin and that it causes brain damage by inducing a non-specific inflammatory response. This response is both dose- and species-dependent. We concluded by discussing the medical implications of the present and proposed uses of colchicine.

Granule populations in oxytocin and abnormal perikarya of the supraoptic nucleus of homozygous Brattleboro rats: effects of colchicine administration

Magnocellular neurones in the supraoptic nucleus of the homozygous Brattleboro rat, which are unable to produce vasopressin, were investigated by immunocytochemistry to identify both the oxytocin cells and the abnormal neurones, which in normal animals would produce vasopressin. The abnormal cell profiles were significantly more rounded than those of the oxytocin cells. Both cell types showed evidence of hyperactivity, but the Golgi apparatus was more extensive in the oxytocin cells, probably as a result of the failure of the abnormal cells to produce vasopressin and its neurophysin and the resultant reduction in hormone packaging. Neurosecretory granules (NSG) 160 nm in diameter were found in the oxytocin perikarya but were absent from the abnormal cell bodies. In addition, a population of small dense granules (SDG) 100 nm in diameter was observed in both types of neurone, in numbers equal to the NSG in oxytocin cells. Injection of a low, non-lethal dose of the axonal transport inhibitor colchicine resulted in a rapid and equal accumulation of both NSG and SDG in oxytocin perikarya and of SDG in the abnormal perikarya after one day. The effects of colchicine were reversed 2-3 days after administration. The SDG, which may contain a co-transmitter or co-hormone substance, are thus produced at a similar rate to NSG, and appear to be transported from the perikarya for subsequent release at the nerve endings.

Immunohistochemical demonstration of differential substance P-, met-enkephalin-, and glutamic-acid-decarboxylase-containing cell body and axon distributions in the corpus striatum of the cat

The immunohistochemical localization of neuronal cell bodies and axons reactive for substance P (SP) and methionine-enkephalin (ME) was investigated in the corpus striatum of the adult cat brain and compared with that of glutamate decarboxylase (GAD), synthetic enzyme for gamma-aminobutyric acid. Striatal cell bodies reactive for ME could be identified only in colchicine treated cats, are medium size, ovoid striatal cells, and are found in large numbers in a more or less even distribution throughout the caudate nucleus, putamen, and nucleus accumbens. The striatal region most densely occupied by ME-immunoreactive cells is the ventral and central part of the caudate head. Modest numbers of larger ME-reactive neurons are dispersed throughout the entopeduncular nucleus and the pars reticulata of the substantia nigra. Striatal cells of medium size reactive for SP could be identified, with or without colchicine, in largest numbers in the medial half of the caudal three-fourths of the putamen and in clusters of irregular size and shape in the head of the caudate nucleus. Cells reactive for SP are also common in layer II and the islands of Calleja of the olfactory tubercle. We could not reliably visualize GAD-positive cell bodies in the striatum, even with colchicine treatment; however, they could be seen readily in all pallidal structures such as the globus pallidus, ventral pallidum, entopeduncular nucleus, and substantia nigra. Axons reactive for ME are found mainly in the globus pallidus where they form a dense and even network throughout the nucleus. The globus pallidus is almost devoid of SP reactivity except near its extreme caudal pole. Conversely, SP-immunoreactive axons form dense meshworks in the entopeduncular nucleus and substantia nigra where ME immunoreactivity is minimal. Fewer, but still ample numbers, of SP-reactive axons are present also in the ventral tegmental and retrorubral areas of the midbrain tegmentum and in the ventral pallidum of the basal forebrain, but only sparse ME-reactive axons are present in these areas. This differential distribution of SP- and ME-containing axons in the pallidal and nigral structures stands in contrast to the relatively homogeneous and dense distribution of GAD-containing axons throughout the dorsal and ventral pallidum, entopeduncular nucleus, and substantia nigra.(ABSTRACT TRUNCATED AT 400 WORDS)

Proopiomelanocortin peptide immunocytochemistry in rhesus monkey brain

The immunocytochemical distribution of proopiomelanocortin (POMC) peptides (beta-endorphin, ACTH, alpha-MSH, 16K fragment) was studied in the brain of the rhesus monkey (Macaca mulatta). Some animals were administered colchicine intracerebroventricularly prior to sacrifice to enhance the visualization of perikaryal immunoreactivity. Immunoreactive perikarya are localized to hypothalamic infundibular nucleus, giving rise to several distinct projections. Rostral projections extend through midline diencephalic and preoptic areas, and enter the telencephalon. Along this course, immunoreactive fibers are seen in midline hypothalamic and preoptic nuclei, nucleus of the diagonal band, olfactory tubercle, nucleus accumbens, bed nucleus of stria terminalis, septum, and other limbic structures in telencephalon. Caudal to the anterior commissure, some fibers ascend dorsally to enter the midline thalamus, which they innervate. Lateral projections of the infundibular perikarya course through the medial-basal hypothalamus, dorsal to the optic tracts, and enter the amygdala region where they innervate more medially situated amygdaloid nuclei. Caudal projections of the POMC neurons also extend through midline diencephalon, some coursing along a periventricular path to innervate midline hypothalamic and thalamic nuclei. This projection extends into the mesencephalic substantia grisea centralis and may also contribute to the innervation of more dorsally situated nuclei in the pons and medulla, such as the parabrachial nuclei and nucleus tractus solitarius. Other caudal projections originating in the hypothalamus course through the ventral tegmentum of mesencephalon and pons and may contribute to the innervation of midline raphe and other ventrally situated nuclei in the pons and medulla. The distribution of immunoreactive perikarya and fibers in the brain of rhesus monkey is strikingly similar to that found in the rat brain. However, subtle differences appear to exist in the innervation patterns of particular brain regions.

A group of neurons highly reactive for enkephalins in the rat hypothalamus

Enkephalin-like immunoreactivity was demonstrated in a group of highly reactive neurons (HRN) of the rat hypothalamus by the biotin-avidin immunohistochemical technique. The location of the HRN spans several nuclei but the consistent immunoreactivity, the constant topography, and the uniform dimensions of the neurons suggest that they belong to one group. At its caudal end the group appears within the rostral dorso-medial nucleus. At the level of the caudal paraventricular nucleus (PVH) the HRN are assembled in a spherical pattern around a subgroup of neurons in the anterior hypothalamus (AH). The HRN then are found in a position directly between the PVH and the fornix. Before the HRN disappear at the level of the caudal preoptic area, many of the HRN become associated with the fornix. The close association of the HRN with the AH subgroup and the fornix suggests that the HRN may influence the activity of these structures. The HRN are small to medium in size and their short processes suggest that the HRN communicate with other neurons in their vicinity. The areas of the hypothalamus in which the HRN are found are involved in neuroendocrine and thermoregulatory functions suggesting that the HRN may play a role in modifying the activity of neurons and fibres involved in these functions.

Age-correlated changes in dopaminergic nigrostriatal perikarya of the C57BL/6NNia mouse

Alterations in neurotransmitter systems of the basal ganglia have been postulated to contribute to the disruption of motor function and balance associated with aging. This study examined nigrostriatal (A9) and mesolimbic (A10) dopamine neurons for qualitative age-correlated changes using fluorescence histochemistry for catecholamines and immunocytochemical techniques for the catecholamine-synthesizing enzyme, tyrosine hydroxylase. Results from this study suggest that age-correlated morphological changes in A9 but not all A10 neurons in the midbrain are present in mature adult (10-month) C57BL/6NNia mice and show a progressive increase in severity until at least 30 months of age. These changes are characterized by a progressive accumulation of lipofuscin in dopamine-containing perikarya, a markedly reduced dopamine content per cell as determined visually by histofluorescence, and an increase in the number of large, fluorescent axonal dilations in dopamine-containing fibers of the mesolimbic and nigrostriatal systems. These data suggest that heterogeneous morphological aging patterns exist within dopamine-containing neurons of the midbrain and that based upon their terminal projection sites, various regions of the striatum and cortex may be differentially affected in the aged brain. In addition, these findings support the belief that age-related changes in neural structure are not generalized to an entire brain nucleus or cell type but are selective for individual cells within an affected area.

The nigrostriatal system and aging

Age-correlated changes in neurotransmitter systems of the basal ganglia have been postulated to contribute to the disruption of motor function and balance associated with aging. This report compared the morphology of nigrostriatal dopamine (DA) neurons of the substantia nigra and ventral tegmental area of the C57B1/6N Nia mouse with the morphology of DA neurons of the nigrostriatal pathway in aged human brain and in one case diagnosed to have senile dementia of the Alzheimer's type (SDAT). Age-correlated changes in fibers of the nigrostriatal pathway in the aged mouse are characterized by an increase in the number of large, fluorescent axonal dilations. Similar axonal swellings were seen in aged human brain. In addition, postmortem SDAT brain was characterized by the presence of large patches or tangles of DA-containing fibers. In the C57B1/6N Nia mouse, age-correlated morphological changes were characterized by a progressive accumulation of cytoplasmic lipofuscin granules and a markedly reduced DA content per cell is determined visually by histofluorescence. Most neurons of the pars compacta of the substantia nigra in postmortem human brain were nonfluorescence and contained heavy deposits of neuromelanin in their cytoplasm. These data suggest that age-correlated morphological changes in fibers of the nigro-striatal system of the aged C57B1/6N Nia mouse are similar in appearance to fibers in the aged human brain and that morphological related changes in dopaminergic cells may play a role in the disruption of motor function associated with advancing age. In addition, the presence of large tangles or patches of DA fibers in postmortem SDAT brain suggests that subcortical DA-containing neurons may also be affected in SDAT.

Enkephalin systems in diencephalon and brainstem of the rat

The immunocytochemical distribution of [Leu]enkephalin and an adrenal enkephalin precursor fragment (BAM-22P) immunoreactivity was investigated in the diencephalon and brainstem of rats pretreated with relatively high doses of colchicine (300-400 micrograms/10 microliters intracerebroventricularly). The higher ranges of colchicine pretreatment allowed the visualization of extensive enkephalin-containing systems in these brain regions, some of which are reported for the first time. Immunoreactive perikarya were found in many hypothalamic and thalamic nuclei, interpeduncular nucleus, substantia nigra, the colliculi, periaqueductal gray, parabrachial nuclei, trigeminal motor and spinal nuclei, nucleus raphe magnus and other raphe nuclei, nucleus reticularis paragigantocellularis, vestibular nuclei, several noradrenergic cell groups, nucleus tractus solitarius, as well as in the spinal cord dorsal horn. In addition to the above regions, immunoreactive fibers were also noted in the habenular nuclei, trigeminal sensory nuclei, locus coeruleus, motor facial nucleus, cochlear nuclei, dorsal motor nucleus of the vagus, and hypoglossal nucleus. When adjacent sections of those stained for [Leu]enkephalin were processed for BAM-22P immunoreactivity, it was found that these two immunoreactivities were distributed identically at almost all anatomical locations. BAM-22P immunoreactivity was generally less pronounced and ws preferentially localized to neuronal perikarya. The results of the present as well as the preceding studies (Khachaturian et al., '83) strongly suggest substantial structural similarity between the adrenal proenkephalin precursor and that which occurs in the brain. Also discussed are some differences and parallels between the distribution of [Leu]enkephalin and dynorphin immunoreactivities.

Short-term effects of intrahypothalamic colchicine

Colchicine was injected in the vicinity of the medial forebrain bundle to cause an accumulation of catecholamines in the lateral hypothalamus proximal to the injection site. Such injections caused severe deficits in consummatory behavior and motor performance within a few hours after injection, which were accompanied by the accumulation of catecholamines in the hypothalamus. Behavioural deficits occurring within 24 h after colchicine injection cannot be attributed to reduced synaptic transmission in the striatum or to dopamine depletion because these events do not commence until 24-48 h after colchicine administration. This study demonstrates the importance of considering all neurochemical changes which accompany catecholamine depletion when assessing the role of the catecholamine-containing system in the regulation of behaviour.

Colchicine reduces myelin thickness and axoplasm volume

A Silastic cuff containing either colchicine (1% w/v) or no colchicine was placed around the lingual disorder tympani nerve of the Mongolian gerbil. After 3 days of exposure to colchicine, the mean period of the myelin sheaths was 23% less than the period observed in nerves treated with cuffs lacking colchicine, while the average number of lamellae was unaltered. At the same time colchicine reduced the volume of axoplasm by an average of 19%, an effect which was independent of fiber diameter.

Dynorphin immunocytochemistry in the rat central nervous system

The distribution of dynorphin in the central nervous system was investigated in rats pretreated with relatively high doses (300-400 micrograms) of colchicine administered intracerebroventricularly. To circumvent the problems of antibody cross-reactivity, antisera were generated against different portions as well as the full dynorphin molecule (i.e., residues 1-13, 7-17, or 1-17). For comparison, antisera to [Leu]enkephalin (residues 1-5) were also utilized. Dynorphin was found to be widely distributed throughout the neuraxis. Immunoreactive neuronal perikarya exist in hypothalamic magnocellular nuclei, periaqueductal gray, scattered reticular formation sites, and other brain stem nuclei, as well as in spinal cord. Additionally, dynorphin-positive fibers or terminals occur in the cerebral cortex, olfactory bulb, nucleus accumbens, caudate-putamen, globus pallidus, hypothalamus, substantia nigra, periaqueductal gray, many brain stem sites, and the spinal cord. In many areas studied, dynorphin and enkephalin appeared to form parallel but probably separate anatomical systems. The results suggest that dynorphin occurs in neuronal systems that are immunocytochemically distinct from those containing other opioid peptides.

Reversible fine structural changes in the supraoptic nucleus of the rat following intraventricular administration of colchicine

A single low dose (3.5 micrograms or 7.0 micrograms) of colchicine injected intraventricularly into normally hydrated or dehydrated (7 or 4 days) and, subsequently, rehydrated (3 hours) rats caused a number of characteristic changes within the perikarya of the supraoptic nucleus. The temporary slow-down of axonal transport of neurosecretory granulated vesicles (NGVs) and their continued synthesis led to a perikaryal accumulation of NGVs, and changes in their electron-density are considered to be indicative of their continued maturation. In some neurons, the biosynthetic pathway appears to be interrupted or temporarily impaired as evidenced by the accumulation of material of varying electron-density and of granules within the cisternae of the rough ER. An increased number of varying types of lysosomes and phagolysosomes is indicative for the disposal of NGVs within the perikaryon. Most of them are, however, removed through resumption of axonal transport which leads to the reestablishment of pre-experimental fine structural characteristics within approximately 9 days. In the osmotically stressed groups, the fine structural changes are more pronounced but equally reversible.

Multiple-rate components of axonally transported proteins in the hypothalamo-neurohypophysial system of the rat

The transport of labeled proteins from the hypothalamus to the neurohypophysis following 35S-methionine injection into the rat supraoptic nucleus was studied using a unique approach adapted for the study of short-axon systems. Multiple-rate components to those found in other neuronal systems were demonstrated. Neurosecretory vesicle-containing proteins (e.g., neurophysins) were transported at fast rates (greater than 120 mm/day), whereas the cytoskeletal protein, actin, moved principally in the slow component of transport. Two-dimensional gel electrophoresis was used to analyze the diverse patterns of labeled proteins found in the various rate components of axonal transport in this system.

Long-term memory: disruption by inhibitors of protein synthesis and cytoplasmic flow

Colchicine (60 micrograms/kg), an inhibitor of axoplasmic transport, administered subcutaneously to mice had no detectable effect on retention when given shortly after active avoidance training, nor did a pretraining injection of anisomycin (ANI) have an amnesic effect. However, when ANI was administered shortly prior to training and colchicine was administered after training, retention performance was impaired. The amnesic effect was dependent on the time at which colchicine was administered. The amnesic effect was also obtained when ANI was combined with either vinblastine (6 micrograms/kg) or podophyllotoxin (3 micrograms/kg), drugs that inhibit axoplasmic transport. Intracerebral injections of colchicine (60 ng to 60 pg) caused amnesia in subjects pretreated with ANI, but not in subjects pretreated with saline. Lumicolchicine, an isomer of colchicine, which has similar central nervous system effects but has a low binding affinity for microtubule protein, did not impair retention in ANI pretreated mice. It is suggested that axonal transport of recently synthesized protein is required for long-term memory storage.

The immunocytochemical localization of enkephalin in the central nervous system of the rat

The immunocytochemical localization of enkephalin-like immunoreactivity (ELI) throughout the rat central nervous system (CNS) was investigated. The detection of ELI-containing structures was facilitated through the use of (1) brains from colchicine-treated rats, (2) the proteolytic pretreatment of sections with pronase and (3) the "double-bridge" staining technique. Our findings confirm the presence of ELI in perikarya, neuronal processes and terminals in many areas of the CNS. In addition, the localization of ELI-containing perikarya is reported for the first time in the following areas: the olfactory bulb, the olfactory tubercle, the lateral preoptic nucleus, several nuclei within the amygdaloid nuclear complex, the hippocampus, the neocortex, the cingulate cortex, the posterior mammillary nucleus, the medial nucleus of the optic tract, the brachium of the inferior colliculus, the ventral tegmental nucleus, the locus ceruleus, the sub-ceruleal region, the lateral trapezoid nucleus, the nucleus reticularis lateralis, and lamina VII of the cervical spinal cord. Our results demonstrate ELI in neurons which are heterogeneous in size, some probably functioning as interneurons and others as projection neurons in different areas of the CNS. The location of these neurons within the brain suggests that these pentapeptides serve diverse functions which include, in addition to nociception, the regulation of neuroendocrine, respiratory, auditory, vestibular, and olfactory functions.

Inhibition of fast axonal transport and microtubule polymerization in vitro by colchicine and colchiceine

The effects of colchicine and colchiceine on fast axonal transport in frog sciatic nerves were studied in vitro. Colchiceine inhibited the transport to about the same extent as colchicine. Preincubation at low temperature potentiated the inhibitory effect of either drug. The polymerization of purified brain tubulin was inhibited by colchiceine at 5-10 times higher concentrations than colchicine. The similarity of the effects obtained with colchicine and colchiceine indicates that both drugs arrest axonal transport by interfering with microtubule function. Colchicine and colchiceine did not affect the levels of high energy phosphates (ATP and CrP) in frog nerves indicating that a reduced energy supply was not responsible for the arrested transport.

Immunohistochemical localization of enkephalin in rat brain and spinal cord

The distribution of immunoreactive enkephalin in rat brain and spinal cord was studied by immunoperoxidase staining using antiserum to leucine-enkephalin ([Leu5]-enkephalin) or methionine-enkephalin ([Met5]-enkephalin). Immunoreactive staining for both enkephalins was similarly observed in nerve fibers, terminals and cell bodies in many regions of the central nervous system. Staining of perikarya was detected in hypophysectomized rats or colchicine pretreated rats. The regions of localization for enkephalin fibers and terminals include in the forebrain: lateral septum, central nucleus of the amygdala, area CA2 of the hippocampus, certain regions of the cortex, corpus striatum, bed nucleus of the stria terminalis, hypothalamus including median eminence, thalamus and subthalamus; in the midbrain: nucleus interpeduncularis, periaqueductal gray and reticular formation; in the hind brain: nucleus parabrachialis, locus ceruleus, nuclei raphes, nucleus cochlearis, nucleus tractus solitarii, nucleus spinalis nervi trigemini, motor nuclei of certain cranial nerves, nucleus commissuralis and formatio reticularis; and in the spinal cord the substantia gelatinosa. In contrast enkephalin cell bodies appear sparsely distributed in the telencephalon, diencephalon, mesencephalon and rhombencephalon. The results of the histochemical staining show that certain structures which positively stain for enkephalin closely correspond to the distribution of opiate receptors in the brain and thus support the concept that the endogenous opiate peptides are involved in the perception of pain and analgesia. The localization of enkephalin in the preoptic-hypothalamic region together with the presence of enkephalin perikarya in the paraventricular and supraoptic nuclei suggest a role of enkephalin in the regulation of neuroendocrine functions.

Reversible hyperphagia and obesity following intracerebral microinjections of colchicine into the ventromedial hypothalamus of the rat

Colchicine, a drug which produces a reversible inhibition of intraaxonal transport and synaptic transmission, was used as a reversible neural blocker to investigate the role of the ventromedial hypothalamus (VMH) in the control of ingestive behavior and body weight regulation. Male Sprague-Dawley rats received intracranial microinjections of colchicine into the VMH. Volume and concentration of the colchicine solution were varied to assess specificity of action and dose-response relationship. When colchicine (2 and 4 microgram) was microinjected bilaterally into the VMH, there was a dose-dependent increase in food and water intakes and body weight gain which lasted several days. The acute period of hyperphagia was followed by a marked depression in feeding which persisted until body weight was lowered to control levels. This suppression of feeding appeared to be a consequence of the preceding period of hyperphagia and obesity, since colchicine-treated rats which were pair-fed with controls to prevent obesity continued to maintain normal food intake and body weight gain when later fed ad libitum. The results of this study confirm the importance of the VMH in the long term regulation of feeding, and indicate that reversible neuronal blocking with colchicine is a useful technique for investigating the neural substrates of feeding and other behaviors.

Scanning microscopy of pituitary vascular casts

Vascular casts of the pituitary-median eminence complex from seventeen adult female rabbits were examined with the scanning electron microscope. The results of this study confirm the presence of a single capillary bed common to the entire neurohypophysis. Arterial supply to the rabbit pituitary is only to the neurohypophysis. A direct supply to adenohypophysis was not found. Within the median eminence there are an external and internal capillary plexus. The internal capillary plexus is directed toward the infundibular recess of the third ventricle. It does not receive a direct arterial supply but derives its blood supply from the external plexus before draining to the adenohypophysis. Vessels of the posterior median eminence are confluent with vessels of the infundibular stem. On the basis of these studies, it is proposed that the entire neurohypophysis, not simply the median eminence, serves as the final common pathway to the glandular pituitary. It is also proposed that in the median eminence, vessels are organized to deliver blood containing hypothalamic releasing and inhibiting hormones as well as posterior lobe neural hormones (antidiuretic hormone and oxytocin) to the ventricular surface for subsequent transport to cerebrospinal fluid and distribution to the brain.