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Biomedical subjects

F E Bloom

Publications and source records attributed to F E Bloom.

At least 199 records · Page 11Linked to original sources
PubMed1986

Immunoelectronmicroscopy of neural antigens on ultrathin frozen sections.

We have utilized immunocryoultramicrotomy to detect synapsin, somatostatin, parvalbumin, and tubulin at the ultrastructural level. Immunocryoultramicrotomy combines informative identification of morphology with accurate immunolabeling. Moreover, since no detergents or organic solvents are used to enable antibody penetration, and since no enzyme marker diffusion occurs, localization of the antigens should be more accurate. Accordingly, it was possible to localize precisely all four antigens within a well-preserved structure. Application of this method has important advantages for high-resolution localization of molecules relevant to neuronal function.

Animals↗
PubMed1986

Neurochemical substrates for opiate reinforcement.

The studies reported herein summarize our work to date aimed at determining the neurochemical substrates for the reinforcing properties of opiates. Rats were trained to self-administer heroin intravenously in daily 3-hour sessions, and pharmacological blockade and neurotoxin-induced lesions were used to define the neurochemical substrates for this reinforcing action. Low-dose DA receptor blockade failed to alter heroin self-administration but significantly increased cocaine self-administration, presumably reflecting a decrease in the reinforcing effectiveness of cocaine. Destruction of presynaptic DA terminals within the N.Acc. produced extinction of cocaine, but not heroin, self-administration. Opiate receptor blockade with systemic naloxone increased heroin, but not cocaine, self-administration. Methylnaloxonium injections into the N.Acc. were effective in increasing heroin self-administration at doses one-eighth those observed for intracerebroventricular injections. Reinforcement has been explored using a place-preference procedure and a self-administration drug-substitution paradigm. Mu/delta agonists such as B-END readily produce a naloxone-reversible place preference. Fentanyl derivatives also produce place preference and substitute for heroin during self-administration. The kappa agonist U50-488 produces place aversion, not place preference, and does not readily substitute for heroin. Altogether, these results suggest that mu/delta receptor subtypes in the region of the N.Acc. may be an important neurochemical substrate for opiate reinforcement.

Animals↗
PubMed1986

The brain-specific gene 1B236 is expressed postnatally in the developing rat brain.

The rat brain-specific polypeptide 1B236 was previously characterized by molecular cloning and nucleotide sequence determination of its mRNA. It has been shown to exist in rat brain in discrete neuronal circuits, primarily as a 100,000 Da glycoprotein. We now have determined the time course of expression of 1B236 mRNA and protein in rat brain during fetal and postnatal development, detecting 1B236 mRNA by RNA blotting and assaying 1B236 protein by electroblotting and radioimmunoassay with antibodies against synthetic peptides. By both indices, expression of the 1B236 gene products is found to be a relatively late event in neuronal development. 1B236 mRNA is first detectable in extracts of whole rat brain at Postnatal Day 5 (PD 5) and increases to a maximum concentration at PD 25. In extracts of dissected brain regions, 1B236 mRNA is first detectable at PD 5 in hindbrain and cerebellum, at PD 9 in midbrain/diencephalon, but not until PD 13 in telencephalon. The appearance of 1B236 protein follows a very similar time course to that of its mRNA in both whole brain and dissected brain regions, suggesting that the expression of the protein during development is regulated largely by transcription of its mRNA. The pattern of 1B236 expression was confirmed by immunocytochemical localization of 1B236 protein: Immunoreactive material can be detected first in spinal cord at PD 3-PD 5 and then appears in progressively more rostral brain regions in increasingly older animals. Several brain regions, however, that do not contain 1B236 immunoreactivity in the adult, such as optic nerve and somatic efferent cranial nerve nuclei, show transient expression of 1B236 during postnatal development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Selective inactivation of opioid receptors in rat hippocampus demonstrates that dynorphin-A and -B may act on mu-receptors in the CA1 region.

Dynorphin-A1-17 and dynorphin-B increased the evoked response of hippocampal CA1 pyramidal cells, as did other opioids tested. Treatment of the hippocampal slice with beta-funaltrexamine, a mu-receptor selective antagonist, blocked the effects of normorphine, dynorphin-A and dynorphin-B, but did not change the response to D-Ala2, D-Leu5-enkephalin. The low potency of kappa selective agonists and the antagonism by beta-funaltrexamine of the dynorphins' effect indicate that kappa-opioid receptors may not be involved in these observed responses. Our data suggest that both mu- and delta-receptors are functionally represented and provide evidence that the dynorphins or their derivatives may also be agonists at the mu-receptor.

Animals↗
PubMed1985

Blockade of nucleus accumbens opiate receptors attenuates intravenous heroin reward in the rat.

A quaternary derivative of naloxone, methyl naloxonium chloride (MN), was administered intracerebrally to rats trained to self-administer heroin intravenously. Increases in intravenous (IV) heroin self-administration rates were found following injections of low doses of MN into the nucleus accumbens (N.Acc), but not following injections of low doses of MN into the ventral tegmental area (VTA). These results were interpreted to suggest that the rewarding properties of IV heroin were decreased following N.Acc opiate receptor blockade. The relative insensitivity of the VTA to MN treatment was taken to suggest that VTA opiate receptors are either not essential or play a secondary role in mediating IV heroin self-administration. The present data support the notion that post-synaptic N.Acc opiate receptors play a crucial role in maintaining IV heroin self-administration.

Animals↗
PubMed1985

Effects of intracerebroventricular administration of methyl naloxonium chloride on heroin self-administration in the rat.

A quaternary derivative of naloxone, methyl naloxonium chloride (MN), was administered intracerebroventricularly (ICV) to rats trained to self-administer heroin intravenously. MN produced a dose-dependent (0.5-4.0 micrograms) increase in responding for heroin. Since MN is unlikely to reach the peripheral circulation in these doses, these results were viewed as strongly supporting the hypothesis that central opiate receptors are solely responsible for mediating the reinforcing properties of heroin during self-administration. In addition, the present study suggests that intracerebral MN injections may prove to be a useful technique in the search for central substrates of heroin reward.

Animals↗
PubMed1985

Vasopressin pressor antagonist injected centrally reverses behavioral effects of peripheral injection of vasopressin, but only at doses that reverse increase in blood pressure.

Previous work in rats (Ader, R. and De Wied, D., Psychon. Sci., 29 (1972) 46-48) has established that subcutaneously (s.c.) injected arginine vasopressin (AVP) prolongs extinction of active avoidance and that this effect could be prevented by pretreatment with the vasopressin antagonist analog [1-deaminopenicillamine, 2-(O-methyl)tyrosine]-beta-arginine vasopressin (dPtyr(Me)AVP). The purpose of the present study was to determine if peripherally administered AVP acts via a peripheral blood pressure effect or by a direct action in the central nervous system. We therefore tested the effects of the antagonist injected intracerebroventricularly (i.c.v.) on the prolongation of active avoidance and on blood pressure effects of s.c. injected AVP. The antagonist (i.c.v.) blocked the behavioral effects of systemically injected AVP only at dose sufficient to block the peripherally mediated pressor response of systemically administered AVP. The results show that peripherally injected AVP acts on peripheral systems and support our hypothesis that the peripheral visceral action of AVP contributed significantly to its behavioral action.

Animals↗
PubMed1985

Vasoactive intestinal polypeptide acts synergistically with norepinephrine to depress spontaneous discharge rate in cerebral cortical neurons.

Cortical neurons are densely innervated by noradrenergic fibers and by intrinsic cortical interneurons containing vasoactive intestinal polypeptide (VIP). Biochemically, VIP and norepinephrine (NE) synergistically interact to stimulate the synthesis of cyclic AMP in cortical slices. Therefore, we sought physiological indices of this peptide-monoamine interaction by applying VIP and NE to single cortical neurons of the rat while recording their spontaneous discharge. VIP applied alone inhibited discharge of 24% and accelerated discharge in 20% of cortical neurons. NE alone had a predominantly depressant effect on the same neurons. However, when VIP was retested during the continuous application of subthreshold currents of NE, VIP exerted predominantly depressant effects. These synergistic inhibitions resulted even in cells previously showing excitations to VIP alone. If VIP alone was depressant, subthreshold NE further enhanced the VIP depression. Subthreshold amounts of phenylephrine, an alpha-adrenoceptor agonist, also produced comparable interactions, suggesting involvement of an alpha receptor, as in the biochemical studies. These results support a peptide-monoamine interaction in cortex that could have important ramifications for neuronal integration.

Action Potentials↗
PubMed1985

Brain-specific polypeptide 1B236 exists in multiple molecular forms.

The COOH-terminal amino acid sequence of the rat brain-specific polypeptide 1B236 was previously deduced from molecular cloning and nucleotide sequence determination of its mRNA and the 1B236 protein shown to exist in the rat brain. The amino acid sequence of 1B236 contained at least three peptide sequences demarcated by pairs of basic amino acids--a structure similar to known neuropeptide and hormone precursors--which suggested that the protein might be processed in vivo to generate peptides. We have developed radioimmunoassays specific for 1B236 with antibodies against three synthetic peptides corresponding to putative cleavage products of this protein and have used these assays to define the molecular forms of 1B236 in rat brain extracts. The most abundant form is of high molecular weight (ca. 100,000) and requires detergent for solubilization; hence, it is probably membrane-bound. However, a small fraction of the high molecular weight material is soluble in the absence of detergent. In addition, several low molecular weight species are detectable in brain extracts prepared under conditions preventing proteolysis. These molecules correspond in size to two of the possible products of proteolytic processing predicted from the amino acid sequence of 1B236. The multiplicity of 1B236 forms, together with other data, suggests that this protein undergoes extensive post-translational modification, including proteolytic processing to generate peptides that may be physiologically relevant.

Animals↗
PubMed1985

Arginine vasopressin, stress, and memory.

Arginine vasopressin (AVP) has been shown to have several non-renal actions including the potentiation of learned avoidance behavior in rats and improvement in cognitive functioning in humans. Research in our laboratory has confirmed these behavioral effects in rats using both peripheral and central injection of AVP. We have begun to examine the physiological basis for these effects. Peripheral administration of a vasopressor AVP antagonist reversed the prolongation of extinction produced by peripherally administered AVP in both active and passive avoidance, but also reversed the aversive unconditioned effects of AVP. However, central administration of the vasopressor AVP antagonist reversed peripheral effects of AVP only at doses shown to act peripherally to reverse vasopressor effects of AVP. An osmotic stress in doses known to liberate endogenous AVP mimicked the behavioral effects of exogenously administered AVP, and this stress effect was reversed by the AVP antagonist. These results support our hypothesis of separate but parallel AVP systems in the pituitary and brain with a role in behavioral adaptation to certain types of stress.

Animals↗
PubMed1985

Neuropeptides and other mediators in the central nervous system.

Some general principles of peptide and other transmitter actions in the CNS may be applicable to determining how central, autonomic, or blood-borne transmitter signals may regulate the responsiveness of the cells of the immune system. For the resolution of how and where transmitters act in the CNS, research in cellular neurobiology has made substantial recent progress in three specific areas of work: neuronal connectivity, synaptic mechanisms, and neuronal transmitters, Together, the new circuits, new transmitters, and new receptor mechanisms provide a rich repertoire of signaling mechanisms that transcend earlier notions of "classical" excitatory or inhibitory transmission modes and that are pertinent to regulation of immune response mechanisms.

Adenylyl Cyclases↗
PubMed1985

Characterization of the prodynorphin and proenkephalin neuropeptide systems in rat hippocampus.

Opioid peptides derived from prodynorphin were localized immunocytochemically to dentate granule cells and mossy fibers of the rat hippocampus with antisera against dynorphin A(1-17) and dynorphin B. Extracts of microdissected hippocampal regions were resolved by reverse phase and molecular exclusion chromatography to identify the molecular forms of the dynorphin A immunoreactivity and to quantify regional contents. Results demonstrated that the relative concentration of dynorphin A within each dissected region of hippocampus agreed well with the distribution of dynorphin A detected by immunocytochemical methods. Immunostaining of proenkephalin-derived opioid peptides, [Leu5]enkephalin and bovine adrenal medullary peptide-22P, was concentrated in cell bodies of the entorhinal cortex, nerve fibers in the perforant pathway, and terminals in the outer molecular layer of the dentate gyrus. Light immunostaining of granule cells and mossy fibers with these antisera was also found. The relative concentration of [Leu5]enkephalin immunoreactivity in each microdissected region of the hippocampus also agreed well with the distribution of [Leu5]enkephalin immunostaining. Chromatography of hippocampal regional extracts demonstrated that the immunoreactivity measured was due to the presence of authentic [Leu5]enkephalin. The probable neurotransmitter function of both [Leu5]enkephalin and dynorphin A was shown by their calcium-dependent release after in vitro depolarization of hippocampal tissue. The reported presence of beta-endorphin in hippocampus was not verified. Comparison of the hippocampal distribution and content of prodynorphin and proenkephalin-derived opioids suggests that separate populations of neurons containing these two peptide families form distinct neurotransmitter systems of roughly equal concentration.

Animals↗
PubMed1985

Corticotropin-releasing factor and behavior.

Corticotropin-releasing factor (CRF) has behavioral activating effects when injected intracerebroventricularly in rats. CRF dose-dependently increased activity in a familiar photocell cage environment. This activation persisted after hypophysectomy, opiate receptor blockade, and low-dose dopamine receptor blockade, which suggests a unique mechanism of action. CRF also improved acquisition of a visual discrimination task. In aversive situations such as an open field test CRF produced behavioral changes consistent with increased emotionality. These results suggest that CRF liberated directly into the central nervous system may have a neurotropic action important for mobilizing behavioral responses to stress.

Amygdala↗
PubMed1985

Immunocytochemical mapping of 1B236, a brain-specific neuronal polypeptide deduced from the sequence of a cloned mRNA.

The 318-amino acid, carboxy-terminal sequence of the putative brain-specific polypeptide 1B236 was deduced from the nucleotide sequence of its cloned brain-specific mRNA. Antisera raised against selected synthetic peptide fragments of this protein were used to map the cellular location of the presumptive gene product in the brains of normal or colchicine-pretreated adult rats. Antisera directed against any of three C-terminally located, but nonoverlapping, nonhomologous, synthetic peptide segments (P5, P6, or P7) produced virtually identical maps of intensely immunoreactive neuropil staining. The immunoreactivity was distributed heterogeneously and was most pronounced within olfactory, somatosensory, and limbic systems, and was more modest in certain motor and auditory structures. In colchicine-pretreated rats, large, multipolar perikarya were observed within the amygdala, caudate-putamen, cingulate, parietal, and piriform cortices, as well as in particular diencephalic and pontine nuclei. Smaller immunoreactive neurons with more limited dendritic extensions were observed in the olfactory bulb, the cerebellar cortex, and the dorsal horn and intermediolateral cell columns of the spinal cord. No immunoreactivity was observed in visceral structures innervated by the autonomic nervous system or in non-neural tissues. In addition to the virtually superimposable maps produced by antisera to all three synthetic fragments selected from the C-terminus of 1B236, some uniquely reactive sites were seen. Antisera to the most N-terminal of the three synthetic immunogens (P5) were reactive with neurons of the medial trapezoid nucleus and in nerve terminals surrounding the deep cerebellar nuclei. Antisera against the most C-terminal synthetic immunogen (P7) were reactive with neurons of the paraventricular and supraoptic hypothalamic nuclei. These data demonstrate that the 1B236 protein is located within selected neuronal elements within functionally related cellular circuits established more formally by other methods. Our data show that protein 1B236-immunoreactive cells share at least the expression of this protein and suggest that these cells may also be related epigenetically or evolutionarily. These data, together with other subcellular, ultrastructural, and electrophysiological properties of 1B236, suggest that this protein could be considered as a prohormone capable of yielding several final candidate transmitter products.

Animals↗