Factors associated with hearing loss in a normal-hearing guinea pig model of Hybrid cochlear implants.

The Hybrid cochlear implant (CI), also known as Electro-Acoustic Stimulation (EAS), is a new type of CI that preserves residual acoustic hearing and enables combined cochlear implant and hearing aid use in the same ear. However, 30-55% of patients experience acoustic hearing loss within days to months after activation, suggesting that both surgical trauma and electrical stimulation may cause hearing loss. The goals of this study were to: 1) determine the contributions of both implantation surgery and EAS to hearing loss in a normal-hearing guinea pig model; 2) determine which cochlear structural changes are associated with hearing loss after surgery and EAS.

Hypothalamic paraventricular 5-hydroxytryptamine inhibits the effects of ghrelin on eating and energy substrate utilization.

Ghrelin microinjections into discrete regions of the hypothalamus, including the paraventricular nucleus (PVN), stimulate eating and promote carbohydrate oxidation, effects similar to PVN microinjection of neuropeptide Y (NPY). We have also reported that NPY's orexigenic and metabolic effects are antagonized by pretreatment with 5-hydroxytryptamine (5-HT) or 5-HT receptor agonists. In order to determine whether 5-HT also inhibits ghrelin's orexigenic and metabolic actions, the present study examined the effects of 5-HT pretreatment on ghrelin-induced alterations in eating and energy substrate utilization following direct injections into the hypothalamic PVN.