Somatostatin-Positive Neurons in the Rostral Zona Incerta Modulate Innate Fear-Induced Defensive Response in Mice

Defensive behaviors induced by innate fear or Pavlovian fear conditioning are crucial for animals to avoid threats and ensure survival.The zona incerta(ZI)has been demonstrated to play important roles in fear learning and fear memory,as well as modulating auditory-induced innate defensive behavior.However,whether the neuronal subtypes in the ZI and specific circuits can mediate the innate fear response is largely unknown.Here,we found that somatostatin(SST)-positive neurons in the rostral ZI of mice were activated by a visual innate fear stimulus.Optogenetic inhibition of SST-positive neurons in the rostral ZI resulted in reduced flight responses to an overhead looming stimulus.Optogenetic activation of SST-positive neurons in the rostral ZI induced fear-like defensive behavior including increased immobility and bradycardia.In addition,we demonstrated that manipulation of the GABAergic projections from SST-positive neurons in the rostral ZI to the downstream nucleus reuniens(Re)mediated fear-like defensive behavior.Retrograde trans-synaptic tracing also revealed looming stimulus-activated neurons in the superior colliculus(SC)that projected to the Re-projecting SST-positive neurons in the rostral ZI(SC-ZIrSST-Re pathway).Together,our study elucidates the function of SST-positive neurons in the rostral ZI and the SC-ZIrSST-Re tri-synaptic circuit in mediating the innate fear response.

Anxiety-Behavior Modulated by Ventral Medial Prefrontal Cortex of Rats Submitted to the Vogel Conflict Test Involves a Local NMDA Receptor and Nitric Oxide

It was demonstrated in the Vogel conflict test (VCT) that the ventral portion of medial prefrontal cortex (vMPFC) of rats is involved with anxiety behavior. Moreover, the vMPFC local glutamatergic and nitrergic system interaction is involved in modulation of fear conditioning, a model of anxiety. To better understand the role of the MPFC-glutamatergic and nitrergic system on the VTC behavior response, male Wistar rats (250 g) were water deprived for 48 h before the VCT. After 24 h of water deprivation, they were subjected to an initial 3-min non-punished (pre-test) drinking session. Twenty-four hours later bilateral microinjections of NMDA-antagonist LY235959 (4 nmol/200 nL), the specific nNOS inhibitor N-Propyl-L-arginine (N-Propyl –0.08 nmol/200 nL), the NO scavenger Carboxi-PTIO (C-PTIO, 2 nmol/200 nL) or 200nL of vehicle were applied in the vMPFC. After 10 min, the animals were submitted to 3-min punished-licking session. LY235959 increased the number of punished licks. Similar to LY235959, both N-Propyl and C-PTIO also increased the number of punished licks. No changes were observed when LY235959, N-Propyl and C-PTIO were micro- injected into vMPFC surrounding structures such as the cingulate cortex area 1, the corpus callosum and the tenia tecta. In control experiments these drugs did not change neither the number of unpunished licks nor had any effect in the tail-flick test. The results show that NO signaling in the vMPFC can modulate anxiety-behavior in the VCT by control punished behavior. Moreover, this NO modulation could be associated with local glutamatergic activation through NMDA receptors.

Neural Circuit Mechanisms Involved in Animals’Detection of and Response to Visual Threat

Evading or escaping from predators is one of the most crucial issues for survival across the animal kingdom.The timely detection of predators and the initiation of appropriate fight-or-flight responses are innate capabilities of the nervous system.Here we review recent progress in our understanding of innate visually-triggered defensive behaviors and the underlying neural circuit mechanisms,and a comparison among vinegar flies,zebrafish,and mice is included.This overview covers the anatomical and functional aspects of the neural circuits involved in this process,including visual threat processing and identification,the selection of appropriate behavioral responses,and the initiation of these innate defensive behaviors.The emphasis of this review is on the early stages of this pathway,namely,threat identification from complex visual inputs and how behavioral choices are influenced by differences in visual threats.We also briefly cover how the innate defensive response is processed centrally.Based on these summaries,we discuss coding strategies for visual threats and propose a common prototypical pathway for rapid innate defensive responses.

Geographical variation in nest defense among cinereous tit populations in China

Behavioral divergence among populations is common across taxonomic groups,still we know very little about anti-predator behaviors.Animal exposure to predation risk is variable in different ecological contexts.In addition,reproduction value of animals in different geographical regions usually varies.In this study,we tested whether cinereous tits Parus cinereus in different populations exhibited nest defense behaviors similar to those of nest or adult predators and whether their nest defense behaviors showed geographical variation.By using field dummy experiments,we observed tits’nest defense behavior in nest predator common chipmunk Tamias sibiricus and red squirrel Sciurus vulgaris,adult predator Eurasian sparrowhawk Accipiter nisus and nonthreatening species Oriental turtle dove Streptopelia orientalis in the ZJ(44°N),DZ(31°N),and DLS(18°N)populations,respectively.The response scores varied significantly across the 4 dummies in ZJ-tits and DLS-tits but did not in DZ-tits.When facing the chipmunk,ZJ-tits showed the highest response score and DZ-tits showed the lowest response score.When facing the squirrel,ZJ-tits showed a higher response score than tits in the other 2 populations.However,tits among the 3 populations responded similarly to a sparrowhawk or dove with slight response behaviors.In addition,response scores to nest predators were positively correlated with brood size across the 3 populations,but no trend was found for sparrowhawks or doves.Our results indicated that the nest defense behaviors of cinereous tits have evolved in response to large-scale geographical variation in ecological contexts and reproduction value.

Influence of"protective"symbionts throughout the different steps of an aphid-parasitoid interaction

Microbial associates are widespread in insects,some conferring a protection to their hosts against natural enemies like parasitoids.These protective symbionts may affect the infection success of the parasitoid by modifying behavioral defenses of their hosts,the development success of the parasitoid by conferring a resistance against it or by altering life-history traits of the emerging parasitoids.Here,we assessed the effects of different protective bacterial symbionts on the entire sequence of the host-parasitoid interaction(i.e.,from parasitoid attack to offspring emergence)between the pea aphid,Acyrthosiphon pisum,and its main parasitoid,Aphidius ervi and their impacts on the life-history traits of the emerging parasitoids.To test whether symbiont-mediated phenotypes were general or specific to particular aphid-symbiont associations,we considered several aphid lineages,each harboring a different strain of either Hamiltonella defensa or Regiella insecticola,two protective symbionts commonly found in aphids.We found that symbiont species and strains had a weak effect on the ability of aphids to defend themselves against the parasitic wasps during the attack and a strong effect on aphid resistance against parasitoid development.While parasitism resistance was mainly determined by symbionts,their effects on host defensive behaviors varied from one aphid-symbiont association to another.Also,the symbiotic status of the aphid individuals had no impact on the attack rate of the parasitic wasps,the parasitoid emergence rate from parasitized aphids nor the life-history traits of the emerging parasitoids.Overall,no correlations between symbiont effects on the different stages of the host-parasitoid interaction was observed,suggesting no trade-offs or positive associations between symbiont-mediated phenotypes.Our study highlights the need to consider various sequences of the host-parasitoid interaction to better assess the outcomes of protective symbioses and understand the ecological and evolutionary dynamics of insect-symbiont associations.