Disruptions in serotonergic regulation of cortical glutamate release in primate insular cortex in response to chronic ethanol and nursery rearing

Early-life stress has been shown to increase susceptibility to anxiety and substance abuse. Disrupted activity within the anterior insular cortex (AIC) has been shown to play a role in both of these disorders. Altered serotonergic processing is implicated in controlling the activity levels of the associated cognitive networks. We therefore investigated changes in both serotonin receptor expression and glutamatergic synaptic activity in the AIC of alcohol-drinking rhesus monkeys. We studied tissues from male rhesus monkeys raised under two conditions: Male rhesus monkeys (1) "mother reared" (MR) by adult females (n=9) or (2) "Nursery reared" (NR), that is, separated from their mothers and reared as a separate group under surrogate/peer-reared conditions (n=9). The NR condition represents a long-standing and well-validated nonhuman primate model of early life stress. All monkeys were trained to self-administer ethanol (4% w/v) or an isocaloric maltose-dextrin control solution. Subsets from each rearing condition were then given daily access to ethanol, water, or maltose-dextrin for 12 months. Tissues were collected at necropsy and were further analyzed. Using real time RT-PCR we found that ethanol-naive, NR monkeys had lower AIC levels of 5-HT(1A) and 5-HT(2A) receptor mRNA compared with ethanol-naive, MR animals. Although NR monkeys consumed more ethanol over the 12-month period compared with MR animals, both MR and NR animals expressed greater 5-HT(1A) and 5-HT(2A) receptor mRNA levels following chronic alcohol self-administration. The interaction between nursery-rearing conditions and alcohol consumption resulted in a significant enhancement of both 5-HT(1A) and 5-HT(2A) receptor mRNA levels such that lower expression levels observed in nursery-rearing conditions were not found in the alcohol self-administration group. Using voltage clamp recordings in the whole cell configuration we recorded excitatory postsynaptic currents in both ethanol-naive and chronic self-administration groups of NR and MR monkeys. Both groups that self-administered ethanol showed greater glutamatergic activity within the AIC. This AIC hyperactivity in MR alcohol-consuming monkeys was accompanied by an increased sensitivity to regulation by presynaptic 5-HT(1A) receptors that was not apparent in the ethanol-naive, MR group. Our data indicate that chronic alcohol consumption leads to greater AIC activity and may indicate a compensatory upregulation of presynaptic 5-HT(1A) receptors. Our results also indicate that AIC activity may be less effectively regulated by 5-HT in ethanol-naive NR animals than in NR monkeys in response to chronic ethanol self-administration. These data suggest possible mechanisms for increased alcohol seeking and possible addiction potential among young adults who had previously experienced early-life stress that include disruptions in both AIC activity and serotonin system dynamics.

The effects of chronic ethanol self-administration on hippocampal serotonin transporter density in monkeys

Evidence for an interaction between alcohol consumption and the serotonin system has been observed repeatedly in both humans and animal models yet the specific relationship between the two remains unclear. Research has focused primarily on the serotonin transporter (SERT) due in part to its role in regulating extracellular levels of serotonin. The hippocampal formation is heavily innervated by ascending serotonin fibers and is a major component of the neurocircuitry involved in mediating the reinforcing effects of alcohol. The current study investigated the effects of chronic ethanol self-administration on hippocampal SERT in a layer and field specific manner using a monkey model of human alcohol consumption. [(3)H]Citalopram was used to measure hippocampal SERT density in male cynomolgus macaques that voluntarily self-administered ethanol for 18 months. Hippocampal [(3)H]citalopram binding was less dense in ethanol drinkers than in controls, with the greatest effect observed in the molecular layer of the dentate gyrus. SERT density was not correlated with measures of ethanol consumption or blood ethanol concentrations, suggesting the possibility that a threshold level of consumption had been met. The lower hippocampal SERT density observed suggests that chronic ethanol consumption is associated with altered serotonergic modulation of hippocampal neurotransmission.

Nucleosome repeat structure is present in native salivary chromosomes of Drosophila melanogaster

The regularly repeating periodic nucleosome organization is clearly resolved in the chromatin of the isolated salivary chromosomes of Drosophila melanogaster. A new microsurgical procedure of isolation in buffer A of Hewish and Burgoyne (1973, Biochem. Biophys. Res. Commun., 52:504-510) yielded native Drosophila salivary chromosomes. These chromosomes were then swollen and spread by a modified Miller procedure, stained or shadowed, and examined in the electron microscope. Individual nucleoprotein fibers were resolved with regularly repeated nucleosomes of approximately 10 nm diameter. Micrococcal nuclease digestion of isolated salivary nuclei gave a family of DNA fragments characteristic of nucleosomes for total chromatin, 5S gene, and simple satellite (rho = 1.688 g/cm3) sequences.

Ultrastructure of polytene chromosomes of Drosophila isolated by microdissection

Drosophila polytene chromosomes prepared by a new micromanipulative procedure, which avoids acid squashing, have been examined at the ultrastructural level in the electron microscope. Puffs at 2B, 68C, 74EF, 75B and 85EF, have been examined in some detail, along with the chromocentre and various interbands. The ultrastructure of these chromosomes, which have never been exposed to acid protein denaturants, compares favourably with that of classical acid-fixed specimens. Ribonucleoprotein particles in puffs are seen to be organized in linear arrays and evidence is adduced for looped transcription units. Particles with characteristic sizes and morphologies are observed near the chromocentre, in puffs and in interbands. In interbands RNP particles and ‘superbead’-like chromatin particles may be distinguished. Drosophila polytene chromosomes isolated by micro-manipulation should prove useful for the localization of native chromosomal proteins at an ultrastructural level.