Biology subjects

Getachew, B.

Publications and source records attributed to Getachew, B..

5 recordsLinked to original sources

bioRxiv2026

Supramammillary projections to the lateral preoptic area drive dopamine release and active behavior

The supramammillary nucleus (SuM) is known to promote active, approach-oriented behaviors by engaging ventral tegmental area (VTA) dopamine neurons projecting to the nucleus accumbens (NAc), primarily via a glutamatergic SuM[->]medial septum (MS) pathway. However, the role of other SuM projections in this process remains unclear. Here we combined anatomical tracing, fiber photometry, chemogenetic, and optogenetic approaches to investigate the SuM[->]lateral preoptic area (LPO) pathway. We found that SuM[->]LPO neurons possess extensive collateral projections and are inhibited during consummatory behavior but activated by aversive and unexpected stimuli. Chemogenetic activation of these neurons reduced water intake and immobility during stress, while inhibition enhanced the appetitive phase for ingestive behavior and fear-related immobility. Optogenetic stimulation of SuM[->]LPO terminals reinforced behavior and elicited dopamine release in the NAc. These findings identify the SuM[->]LPO pathway as a distinct circuit that, alongside the SuM[->]MS pathway, engages mesolimbic dopamine signaling to facilitate active behavioral responses to environmental challenges.

neuroscience↗

bioRxiv2026

Reinforcing Nicotine Doses Activate Supramammillary VGluT2 Neurons in Mice

BackgroundAlthough nicotine reinforcement is often attributed to mesolimbic dopamine neurons in the ventral tegmental area, accumulating evidence indicates that additional brain circuits contribute to its reinforcing effects. AimsThe hypothalamic supramammillary region (SuM) has been implicated as one such substrate, yet the cellular targets and circuit mechanisms through which nicotine engages this region remain poorly understood. MethodsWe combined RNAscope in situ hybridization to identify nicotinic acetylcholine receptor (nAChR) subunits, intravenous nicotine self-administration in mice to determine doses that reliably support reinforcement, and fiber photometry to monitor calcium activity in SuM VGluT2 neurons in vivo. ResultsMice exhibited reliable nicotine self-administration across a range of doses under fixed-ratio and progressive-ratio schedules. RNAscope analysis revealed prominent expression of the {beta}2 nAChR subunit in VGluT2-expressing neurons projecting from the SuM to the medial septum. Fiber photometry recordings showed that reinforcing doses of nicotine produced rapid, infusion-locked increases in GCaMP signals in SuM VGluT2 neurons. ConclusionsThese findings identify nAChR-expressing SuM neurons as a candidate circuit substrate engaged by reinforcing doses of nicotine and extend current models of nicotine reinforcement beyond canonical mesolimbic dopamine pathways.

neuroscience↗

bioRxiv2026

Orexinergic Input to the Supramammillary Region Links Threat Salience to Approach Behavior and Dopamine Release

Orexin (hypocretin) neurons (OXN) broadcast arousal-related signals across the forebrain, yet how their inputs shape motivated behavior remains poorly understood. The supramammillary region (SuM), a posterior hypothalamic structure implicated in arousal, active coping and reward-seeking, receives dense orexin innervation. Here, we define how orexinergic terminals in the SuM (OXNSuM) integrate threat salience with approach motivational processes. Using viral tracing and RNAscope, we show that SuM neurons express both orexin receptor subtypes, with type 2 receptors predominating. Fiber photometry recordings from OXNSuM terminals reveal strong activation by footshock and conditioned threat cues, modest responses to salient sensory stimuli, and pronounced suppression during water consumption. Optogenetic stimulation of OXNSuM terminals reinforces instrumental responding, biases real-time place preference, and elicits rapid, stimulation-locked dopamine release in the nucleus accumbens. These findings identify an orexin-to-SuM pathway that is engaged by uncertainty and threat yet promotes approach behavior through coupling to mesolimbic dopamine, revealing a mechanism linking hypothalamic arousal signals to adaptive motivational responses. SIGNIFICANCE STATEMENTThe supramammillary region (SuM) has emerged as a critical node linking arousal, threat processing, and motivated behavior, yet the sources and functions of its modulatory inputs remain unclear. Here, we identify orexinergic projections to the SuM as a circuit mechanism that couples threat-related salience with approach behavior and nucleus accumbens dopamine signaling. We show that orexin terminals in the SuM are activated by stressful and uncertain stimuli but suppressed during consummatory behavior, and that selective activation of these terminals is positively reinforcing and drives rapid dopamine release. These findings reveal a pathway through which orexin neurons promote active coping and reward-seeking, advancing our understanding of how hypothalamic neuromodulation shapes mesolimbic function and adaptive behavioral responses.

neuroscience↗

bioRxiv2025

Cryopreservation of Platynereis dumerilii larvae

The marine annelid Platynereis dumerilii is a functional molecular model organism for developmental, evolutionary and chronobiological studies. Research on Platynereis is rapidly growing, and with it, the number of genetic variants that laboratories isolate or generate and must subsequently maintain and propagate. Therefore, there is an urgent need to alleviate the burden of live culture maintenance by developing cryopreservation techniques for this species. We report the first cryopreservation protocol for P. dumerilii larvae, which combined with a careful post-thawing culturing regime, allowed us to obtain animals that survived to adulthood and successfully reproduced. Our experiments show highest survival rate in 6 - 8 day-old larvae. Equilibration with cryoprotecting agents takes 1h in 5% (v/v) Me2SO + 0.1%(v/w) sucrose, followed by transfer to 0.25ml straws. The protocol cools larvae at 2,5{degrees}C/min from 20{o}C to -35{degrees}C using a programmable freezer, followed by a rapid transfer to liquid N2. Larvae are thawed in a water bath at 18{degrees}C. The post-thaw larvae feeding regime consisted of 50% Tetraselmis + 50 % diatom strains mixture (Grammatophora marina and Nitzschia laevis). The maximum survival obtained with this protocol so far produced 34% survival after [~]5 months.

zoology↗

bioRxiv2024

Df-1 Cell Adaptation and Immune Responses of Lc-75 Vaccinal Strain of Infectious Bursal Disease Virus in Chicken

The current Infectious bursal disease virus (IBDV) vaccine strain of LC-75 in Ethiopia is being produced through chicken embryo fibro blast cell which has short lifespan and limited need of specific pathogen free eggs. Ideally, vaccine should have better longevity and being effective in cost and time. Experimental research was conducted to adopt DF-1 cell and to validate the immune responses, immunosuppressive effect and immunogenicity tests, of LC-75 vaccinal strain of Infections bursal diseases virus A total of 76 chickens were used for these experiments. The seroconversion rate of the vaccine were measured using haemaglutination inhibition (HI) test in the vaccinated two experiment groups, adapted IBDV and Newcastle vaccines at two weeks interval for the first group and only Newcastle vaccine for the second experiment groups. To perform the immunogenicity test, two groups having 20 chickens per group were used and samples of serum were taken on 0-, 7-, 14- and 28-days post vaccinations and subjected to indirect ELISA test. The group that received both vaccine types produced haemagglutination inhibition titer (HIT) of 97.33{+/-}22.49 whereas the other group that received only Newcastle vaccine produced 124{+/-}24.92. The control group always showed no detectable antibody while the vaccinated group was able to produce average antibody S/P values of 0.00 {+/-} 0.01 at day 0, 0.02{+/-} 0.01 at day 7, 1.05{+/-}0.10 at day 14 and 0.83{+/-}0.05 at day 28. RT-PCR using a 400 bp IBDV viral protein 2(VP2) specific primer resulted from positive bands in all samples. In conclusion, the vaccinal strain was able to replicate and adapt on the DF-1 cells and it was found to be immunogenic as well as less immunosuppressive.

microbiology↗