Neural activation patterns associated with mouthbrooding, maternal care, infanticide and fry release in an African cichlid fish.

Parental care has evolved several times and is present across taxa. Parental care behaviors, such as food provisioning and protection, are critical for offspring success. However, infanticide can co-exist with parental care in the same species. The mechanisms underlying the switch from care to consumption and from offspring dependence to independence are relatively unknown, especially in fishes, the oldest and largest group of vertebrates. Mouthbrooding, an extreme example of parental care present in dozens of genera of fishes, provides an excellent opportunity to investigate the brain regions important for parental care. The maternal mouthbrooding African cichlid fish Astatotilapia burtoni broods developing young inside the mouth for approximately 14 days, then provides post-release maternal care by protecting fry inside the mouth when threatened. Following the post-release maternal care phase, females can exhibit infanticide and consume their own offspring. We used immunohistochemistry for the neural activation marker pS6 to identify differences in neural activation among mouthbrooding, maternal-care-providing and infanticide-exhibiting females, and between pre- and post-release fry. We identified five brain regions (Dc-5, ATn, nPPa, Vd-c and Dl-g) that are differentially activated among mouthbrooding, maternal care and infanticide females as well as six regions (Dm, Vv, Vd, Vs-m, TPp, PGZ and INL of retina) differentially activated between pre- and post-release fry. This study identifies both shared and distinct circuitry that may support transitions between parental care states and from care to infanticide, as well as regions in developed fry that support the transition from pre- to post-release.

Soft, bioresorbable coolers for reversible conduction block of peripheral nerves.

Implantable devices capable of targeted and reversible blocking of peripheral nerve activity may provide alternatives to opioids for treating pain. Local cooling represents an attractive means for on-demand elimination of pain signals, but traditional technologies are limited by rigid, bulky form factors; imprecise cooling; and requirements for extraction surgeries. Here, we introduce soft, bioresorbable, microfluidic devices that enable delivery of focused, minimally invasive cooling power at arbitrary depths in living tissues with real-time temperature feedback control. Construction with water-soluble, biocompatible materials leads to dissolution and bioresorption as a mechanism to eliminate unnecessary device load and risk to the patient without additional surgeries. Multiweek in vivo trials demonstrate the ability to rapidly and precisely cool peripheral nerves to provide local, on-demand analgesia in rat models for neuropathic pain.