Mushroom body ablation impairs short-term memory and long-term memory of courtship conditioning in Drosophila melanogaster

We have evaluated the role of the Drosophila mushroom bodies (MBs) in courtship conditioning, in which experience with mated females causes males to reduce their courtship toward virgins (Siegel and Hall, 1979). Whereas previous studies indicated that MB ablation abolished learning in an olfactory conditioning paradigm (deBelle and Heisenberg, 1994), MB-ablated males were able to learn in the courtship paradigm. They resumed courting at naive levels within 30 min after training, however, while the courtship of control males remained depressed 1 hr after training. We also describe a novel courtship conditioning paradigm that established long-term memory, lasting 9 days. In MB-ablated males, memory dissipated completely within 1 day. Our results indicate that the MBs are not required for learning and immediate recall of courtship conditioning but are required for consolidation of short-term and long-term associative memories.

Rhythms of Drosophila period gene expression in culture

The Drosophila clock genes period (per) and timeless (tim) have been studied behaviorally and biochemically, but to date there has been no viable culture system for studying the cell biology of the Drosophila clock. We have cultured pupal ring glands attached to the central nervous system and observed rhythms of period gene expression in the prothoracic gland for 4-7 days. A daily rhythm of Per protein can be entrained by light in culture, even when neural activity is blocked by tetrodotoxin. In cultures maintained for a week in constant darkness, a per-luciferase reporter gene revealed circadian rhythms of bioluminescence. As the first circadian culture system from Drosophila, the prothoracic gland provides unique advantages for investigating the interactions between clock genes and cellular physiology.

A period (per)-like protein exhibits daily rhythmicity in the suprachiasmatic nuclei of the rat

The period (per) gene of Drosophila melanogaster is considered an important biological clock gene, since it regulates multiple behavioral rhythms. Per mRNA and protein exhibit circadian rhythms in the fruitfly brain and these rhythms appear to influence each other through a feedback loop. More recently, using the same antibody as was used in the Drosophila studies, PER-like proteins were detected in the suprachiasmatic nuclei (SCN) of male rats. This region of the brain is considered to be a major neural circadian pacemaker in mammals. The purpose of this study was to confirm that PER-like proteins are detectable in the SCN of female rats and to determine whether PER-like proteins exhibit a circadian rhythm. Female rats were killed at several times of day under both light/dark and constant conditions. Using the same anti-PER antibody in Western blots with Enhanced Chemiluminescence (Western-ECL) detection, the levels of the PER-like proteins were quantified in the SCN and cerebral cortex. The antibody identified a doublet band of approximately 170-160 kDa and a single band at 115 kDa. Of the three PER-like proteins only the largest exhibited a daily rhythm in the SCN, which peaked in the middle of the dark and attained its nadir around lights off; levels during the light were intermediate with a tendency towards a second drop around lights on. This rhythm did not persist under constant dim red light.(ABSTRACT TRUNCATED AT 250 WORDS)

An antibody to the Drosophila period protein labels antigens in the suprachiasmatic nucleus of the rat

Cell bodies in the rat suprachiasmatic nucleus (SCN) were labeled with an antibody against a small domain of the period (per) protein, the product of a gene in Drosophila that regulates circadian rhythms. In immunoblots of SCN protein extracts, the antibody recognized a band of approximately 115 kD, as well as a heterogeneous antigen ranging from 160 kD to 170 kD. The antibody was found in previous studies to label putative circadian pacemaker neurons in Aplysia and Bulla, as well as the cellular sites of per expression in flies. Taken together, these results suggest that the region of the per protein recognized by this antibody may be widely conserved in neuronal circadian pacemakers.

Circadian fluctuations of period protein immunoreactivity in the CNS and the visual system of Drosophila

When the protein encoded by the period (per) gene, which influences circadian rhythms in Drosophila melanogaster, was labeled with an anti-per antibody in adult flies sectioned at different times of day, regular fluctuations in the intensity of immunoreactivity were observed in cells of the visual system and central brain. These fluctuations persisted in constant darkness. Time courses of the changing levels of staining were altered in the per-short mutant: in light/dark cycles, the phase was earlier than in wild-type, and in constant darkness the period was shorter. In a per-long mutant and in behaviorally subnormal germline transformants (involving transduced per DNA), staining intensities were much fainter than in wild-type. Factors involved in initiating or maintaining the per protein cycling were investigated by examining the immunoreactivity in visual system mutants and by exposing wild-type flies to altered light/dark regimes. These genetic and environmental manipulations affected the expression of the per protein in ways that usually parallelled their effects on circadian behaviors.

An antibody to the Drosophila period protein recognizes circadian pacemaker neurons in Aplysia and Bulla

The molecular mechanisms of the pacemakers underlying circadian rhythms are not well understood. One molecule that presumably functions in the circadian clock of Drosophila is the product of the period (per) gene, which dramatically affects biological rhythms when mutated. An antibody specific for the per protein labels putative circadian pacemaker neurons and fibers in eyes of two marine gastropods, Aplysia and Bulla. As was found for the Drosophila per protein, there is a daily rhythm in the levels of the per-like antigen in Aplysia eyes. Thus, certain molecular features of the per protein, as well as aspects of the temporal regulation of its expression, may be conserved in circadian pacemakers of widely divergent species.

Antibodies to the period gene product of Drosophila reveal diverse tissue distribution and rhythmic changes in the visual system

Polyclonal antibodies were prepared against the period gene product, which influences biological rhythms in D. melanogaster, by using small synthetic peptides from the per sequence as immunogens. The peptide that elicited the best antibody reagent was a small domain near the site of the pers (short period) mutation. Specific immunohistochemical staining was detected in a variety of tissue types: the embryonic CNS; a few cell bodies in the central brain of pupae; these and other cells in the central brain of adults, as well as imaginal cells in the eyes, optic lobes, and the gut. The intensity of per-specific staining in the visual system was found to oscillate, defining a free-running circadian rhythm with a peak in the middle of the night.

Proctolin in identified serotonergic, dopaminergic, and cholinergic neurons in the lobster, Homarus americanus

In order to explore the functions of the peptide proctolin in the lobster nervous system, 3 classes of neurons showing proctolin-like immunocytochemical staining were selected for study. These neurons were identified on the basis of physiological and/or morphological criteria, isolated by dissections, and analyzed with biochemical methods to determine whether they contained authentic proctolin and which classical neurotransmitters coexisted with the peptide. Pairs of large proctolin-immunoreactive neurons in fifth thoracic and first abdominal ganglia were identified as serotonin-immunoreactive neurons (Beltz and Kravitz, 1983, 1987) by staining serial sections of the ganglia alternately with the 2 antisera. Physiologically identified cells, dissected from the ganglia and analyzed with high-performance liquid chromatography (HPLC), contained approximately 20 microM proctolin and 0.5 mM serotonin. A large proctolin-immunoreactive neuron in the circumesophageal ganglion was identified as the lobster homolog of a dopaminergic neurosecretory cell found in other crustaceans (Cooke and Goldstone, 1970). The large lobster cell stained with antityrosine hydroxylase antiserum, and synthesized 3H-dopamine from 3H-tyrosine. Dissected cell bodies, analyzed by HPLC, contained approximately 25 microM proctolin. Proctolin-immunoreactive sensory neurons were identified as large stained fibers that terminated in sensory dendrites of the oval organ mechanoreceptor in the scaphognathite (Pasztor, 1979; Pasztor and Bush, 1982). The largest sensory fiber was isolated for biochemical studies. It synthesized 3H-acetylcholine from 3H-choline and, by HPLC analysis, was found to contain approximately 3 microM proctolin. Thus, proctolin coexists with different conventional transmitters in several classes of identified lobster neurons. Investigations of the actions of proctolin in these different contexts should contribute to a more complete understanding of the diverse functions of neuropeptides and their roles as cotransmitters.

Modulatory action and distribution of the neuropeptide proctolin in the crustacean stomatogastric nervous system

Immunocytochemical methods were used to map the distribution of proctolinlike immunoreactivity in the stomatogastric nervous systems (stomatogastric ganglion (STG), paired commissural ganglia (CG), oesophageal ganglion (OG), and connecting nerves) of three crustacean species: Panulirus interruptus, Cancer borealis, and Homarus americanus. Although the patterns of proctolinlike staining were similar among the three species, some differences were also observed. Over 70% of the proctolinlike material in STGs, as measured by radioimmunoassay, was indistinguishable from authentic proctolin in reverse-phase high-performance liquid chromatography. Bath application of proctolin to STGs from Cancer and Panulirus induced characteristic and robust (though somewhat different) changes in their motor patterns. The threshold concentration was approximately 10(-9)M proctolin, and the effects were dose-dependent. These data suggest that the neuropeptide proctolin serves as a neuromodulator of the stomatogastric ganglion.

Mapping of proctolinlike immunoreactivity in the nervous systems of lobster and crayfish

Whole-mount immunocytochemical techniques have been used to map candidate proctolin-containing cells in the central nervous systems of the lobster, Homarus americanus, and the crayfish, Procambarus clarkii. Proctolinlike immunoreactivity was detected in cell bodies and neuropil regions in all central ganglia, and immunoreactive axons were detected in most interganglionic connectives and nerve roots. Cell body staining was confined to fewer than 2% of all cells. Immunoreactive neurons include motoneurons, sensory neurons, neurosecretory cells, and interneurons. Colocalization of the proctolinlike antigen with other neurotransmitters was indicated in a number of cases. Many aspects of the distribution of immunoreactivity were similar in lobster and crayfish; however, staining differences were detected in a number of identified neurons and neural groups, including neurons that innervate the pericardial organs and hindgut motoneurons. Further studies of such neurons might provide interesting clues about the physiological functions of proctolin and the evolution of peptide transmission.

Proctolin in the lobster nervous system

The pentapeptide proctolin (Arg-Tyr-Leu-Pro-Thr) is present in high concentrations in neurosecretory organs of the lobster, Homarus americanus. The central nervous system contains ca. 1400 proctolin-immunoreactive neurons, which appear to serve a variety of different functions. Some of these neurons have been specifically identified and analyzed biochemically to determine which classical neurotransmitters coexist with the peptide. These include: serotonin-proctolin cell pairs in the fifth thoracic and first abdominal ganglia; a large dopamine-proctolin neuron in the circumesophageal ganglion; and cholinergic-proctolin sensory neurons which innervate a mechanoreceptor in the scaphognathite. With these identified neurons we have begun to investigate the physiological actions of proctolin, the interactions between cotransmitters, and the development of multiple transmitter phenotypes in individual neurons.

Proctolin in the lobster: the distribution, release, and chemical characterization of a likely neurohormone

A radioimmunoassay, immunohistochemical techniques, and high pressure liquid chromatography (HPLC) methods have been developed for the study of the pentapeptide proctolin in the lobster Homarus americanus. Proctolin-like immunoreactivity is present in nearly every portion of the lobster nervous system; immunoreactivity is found in the brain, in each of the ganglia and connectives of the ventral nerve cord, and in many of the nerve roots that emerge from the cord. The greatest amounts are found in the pericardial organs, which are well known neurosecretory structures, and these structures have been selected for more detailed study. The immunoreactive material in the pericardial organs appears to be authentic proctolin. This material co-migrates with synthetic proctolin in two HPLC systems. Furthermore, a peptide that is purified from pericardial organs by HPLC is indistinguishable from synthetic proctolin in high resolution fast atom bombardment mass spectrometry. Cytochemistry reveals that the surface of the pericardial organs is densely covered with immunoreactive varicosities. No cell bodies that stain for proctolin are found in the pericardial organs, and the cells that give rise to the varicosities have not yet been located. The nerve endings in pericardial organs are capable of releasing proctolin-like material when depolarized in the presence of Ca++. These findings suggest that proctolin is a neurohormone in the lobster.