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Intranasal administration is emerging as a very promising route to deliver therapeutics to the brain. We have recently shown that the intranasal delivery of progesterone at 8 mg/kg is neuroprotective after stroke in male mice. To explore the translational potential of intranasal progesterone treatment, we performed a dose-response study and analyzed outcomes at 48 h after middle cerebral artery occlusion (MCAO). The effects on functional outcomes at long-term were examined by using the optimal dose. In the first experiment, male C57BL/6JRj mice were treated with progesterone at 8, 16 or 24 mg/kg, or with placebo at 1, 6 and 24 h post-MCAO. Our results show that the dose of 8 mg/kg was optimal in counteracting the early histopathological impairments as well as in improving functional recovery. Steroid profiling in plasma showed that the dose of 8 mg/kg is the one that leads to sustained high levels of progesterone and its neuroactive metabolites. In the second experiment, the dose of 8 mg/kg was used and analyzes were performed at 2, 7 and 21 days post-MCAO. Progesterone increased survival, glycemia and body weight. Furthermore, progesterone decreased neurological deficits and improved performances of mice on the rotarod and pole as early as 2 days and up to 21 days post-MCAO. These findings show that intranasal administration of progesterone has a significant translational potential as a cerebroprotective treatment after stroke that can be effective to reduce mortality, to limit tissue and cell damage at the acute phase; and to confer a long-term functional recovery., Competing Interests: Declaration of competing interest None., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This study determined the effects of intranasal pregnenolone (IN-PREG) on acetylcholine (ACh) levels in selected areas of the rat brain, using in vivo microdialysis. Previous studies showed that PREG rapidly reaches the rodent brain after intranasal administration and that direct infusion of PREG and PREG-S into the basal forebrain modulates ACh release in frontal cortex, amygdala, and hippocampus. In the present study, we investigated the effects of IN-PREG on the cholinergic system in the rat brain. In the first experiment, IN-PREG (5.6 and 11.2 mg/ml) or vehicle was applied bilaterally, and we hypothesized that IN-PREG would increase ACh levels in amygdala, hippocampus, and frontal cortex, relative to baseline and vehicle. Dialysate was collected for 100 min, based on pilot data of duration of effect. Bilateral IN-PREG (5.6 and 11.2 mg/ml) increased frontal cortex and hippocampal ACh relative to both baseline and vehicle. Moreover, 11.2 mg/ml PREG increased ACh in the amygdala relative to baseline, the lower dose, and vehicle. Therefore, in the second experiment, IN-PREG (11.2 mg/ml) was applied only into one nostril, with vehicle applied into the other nostril, in order to determine whether ACh is predominantly increased in the ipsilateral relative to the contralateral amygdala. Unilateral application of IN-PREG increased ACh in the ipsilateral amygdala, whereas no effect was observed on the contralateral side, suggesting that PREG was transported from the nostrils to the brain via the olfactory epithelial pathway, but not by circulation. The present data provide additional information on IN-PREG action in the cholinergic system of frontal cortex, amygdala, and hippocampus. This may be relevant for therapeutic IN application of PREG in neurogenerative and neuropsychiatric disorders., (© 2019 International Society for Neurochemistry.)

This study investigated the effect of intranasal administration of progesterone on the early brain mitochondrial respiratory chain dysfunction and oxidative damage after transient middle cerebral occlusion in male and female mice. We showed that progesterone (8 mg/kg at 1 h post-middle cerebral occlusion) restored the mitochondrial reduced glutathione pool and the nicotinamide adenine dinucleotide-linked respiration in both sexes. Progesterone also reversed the decrease of the flavin adenine dinucleotide-linked respiration, which was only observed in females. Our findings point to a sex difference in stroke effects on the brain respiratory chain and suggest that the actions of progesterone on mitochondrial function may participate in its neuroprotective properties., (© The Author(s) 2015.)

Progesterone is a potential neuroprotective agent for cerebral stroke. One of the STAIR's recommendations is to test different routes of delivery of therapeutic agents. Here, we investigated the neuroprotective efficacy of intranasal delivery of progesterone in oleogel. Male mice were subjected to transient middle cerebral occlusion (MCAO) for 1 h. Mice received intranasal or intraperitoneal administrations of progesterone (8 mg/kg) at 1, 6, and 24 h post-MCAO. Plasma and brain levels of steroids were measured by gas chromatography-mass spectrometry 2 and 24 h after the last administration of progesterone. Behavioral and histopathological analyzes were performed at 48 h post-MCAO. For blood-brain barrier (BBB) permeability analysis, mice received one intranasal administration of progesterone or placebo at reperfusion and Evans Blue and sodium fluorescein extravasations were assessed at 4 h post-MCAO. Two hours after its nasal administration, progesterone reached elevated levels in brain and plasma and was bioconverted to its 5α-reduced metabolites and to 20α-dihydroprogesterone. However, brain levels of progesterone and its metabolites were about half those measured after intraperitoneal injections, whereas levels of 11-deoxycorticosterone and corticosterone were 5-times lower. In contrast, after 24 h, higher levels of progesterone were measured in brain and plasma after intranasal than after intraperitoneal delivery. Intranasal progesterone decreased the mortality rate, improved motor functions, reduced infarct, attenuated neuronal loss, and decreased the early BBB disruption. This study demonstrates a good bioavailability, a prolonged absorption and a good neuroprotective efficacy of intranasal delivery of progesterone, thus potentially offering an efficient, safe, non-stressful and very easy mode of administration in stroke patients., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Progesterone is commonly considered as a female reproductive hormone and is well-known for its role in pregnancy. It is less well appreciated that progesterone and its metabolite allopregnanolone are also male hormones, as they are produced in both sexes by the adrenal glands. In addition, they are synthesized within the nervous system. Progesterone and allopregnanolone are associated with adaptation to stress, and increased production of progesterone within the brain may be part of the response of neural cells to injury. Progesterone receptors (PR) are widely distributed throughout the brain, but their study has been mainly limited to the hypothalamus and reproductive functions, and the extra-hypothalamic receptors have been neglected. This lack of information about brain functions of PR is unexpected, as the protective and trophic effects of progesterone are much investigated, and as the therapeutic potential of progesterone as a neuroprotective and promyelinating agent is currently being assessed in clinical trials. The little attention devoted to the brain functions of PR may relate to the widely accepted assumption that non-reproductive actions of progesterone may be mainly mediated by allopregnanolone, which does not bind to PR, but acts as a potent positive modulator of γ-aminobutyric acid type A (GABA(A) receptors. The aim of this review is to critically discuss effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABA(A) receptors, with main focus on the brain., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Neurosteroids hold great promise for the treatment of diseases of the central nervous system (CNS). We compared the uptake by 11 brain regions and appearance in blood of tritium-labeled pregnenolone and progesterone after intranasal and intravenous (IV) injection. Both neurosteroids appeared in blood and brain after either method of administration, but with important differences in uptake. Bioavailability based on appearance in arterial serum showed that about 23% and 14% of the intranasal administered doses of pregnenolone and progesterone, respectively, entered the blood. Brain levels were about two fold lower after intranasal administration for the two neurosteroids. With intranasal administration, brain levels of the two steroids did not vary over time (2-120 min), whereas brain levels were higher early (10 min or less) after i.v. administration. With i.v. administration, uptake by brain regions did not vary, whereas the olfactory bulb, hippocampus, and hypothalamus had high uptake rates after intranasal administration. Intranasal administration of prenenolone improved memory, whereas progesterone decreased anxiety, thus demonstrating that therapeutic levels of neurosteroids can be delivered to the brain by intranasal administration. The neurosteroids were rapidly degraded after i.v. or intranasal delivery, but pregnenolone was more resistant to degradation in the brain after intranasal administration and in serum after i.v. administration. These results show that either the i.v. or intranasal routes of administration can deliver neurosteroids to blood and brain, but that the two routes have significant differences with intranasal administration favoring some brain regions., (Published by Elsevier B.V.)

Intranasal (i.n.) administration has emerged as a strategy to deliver therapeutics to the brain. Here, we compared i.n. and intravenous (i.v.) administration for testosterone. About 75% of the i.n. administered testosterone entered the blood. However, whole brain levels of testosterone were about twice as high after i.n. administration as after i.v. administration. About two-thirds of the testosterone entering the brain after i.n. administration did so by direct entry by nasal routes and the remainder indirectly by first entering the blood and then crossing the blood-brain barrier. All brain regions except the frontal cortex had higher levels of testosterone after i.n. administration than after i.v. administration, although the differences among brain regions varied much more for the i.n. route. The olfactory bulb, hypothalamus, striatum, and hippocampus had the highest levels after i.n. administration. The brain uptake pattern suggested a variety of distribution routes likely involving the cerebrospinal fluid, diffusion through brain tissue, and transport through nerve projections. Regional distribution patterns were similar after either i.n. or i.v. administration, suggesting that the dominant factor determining distribution/retention was the same for either route of administration. We conclude that the i.n. administration route delivers testosterone systemically and can target the brain, especially the olfactory bulb, hypothalamus, striatum, and hippocampus.

Female mate choice involves the comparative evaluation of potential mates. Females use a pooled comparison of sampled males to maximize the perceived reproductive fitness of their partner, implying the memorization of sampled males. However, hormonal and reproductive states influence female choosiness, and women's preference and memory for masculinity. Here, we investigated whether testosterone biases memory processes in women towards male faces using functional MRI. A single nasal testosterone dose was administered to healthy women in their early follicular phase, in a double-blind, placebo-controlled, crossover design. Testosterone increased the difference in reaction times to categorize male and female faces during encoding, without influencing subsequent recognition accuracy or response bias. The imaging results showed that testosterone shifted memory formation in the hippocampus and inferior temporal gyri from the encoding of female faces towards the encoding of male faces. In contrast, testosterone shifted memory formation in the left inferior frontal gyrus from the encoding of male faces towards the encoding of female faces. Furthermore, the hippocampal contribution to memory retrieval also shifted from female towards male faces. These results indicate that testosterone biases memory processes towards the relatively automatic encoding and retrieval of males in temporal brain regions and elaborate encoding of females in frontal brain regions, suggesting that testosterone may support female mate sampling and comparison by biasing automatic memory processes towards the encoding and retrieval of potential mates.