Nicotinic excitation of serotonergic projections from dorsal raphe to the nucleus accumbens.

Tobacco use is a major public health problem, and although many smokers report that they want to quit, only a small percentage succeed. Side effects associated with nicotine withdrawal, including depression, anxiety, and restlessness, certainly contribute to the low success rate. The dorsal raphe nucleus (DRN) is a serotonergic center with many functions, including control of mood and emotional state. We investigated the effect of nicotine on DRN neurons that project to the nucleus accumbens (NAc), an area involved in reward-related behaviors. Using a retrograde labeling method, we found that 75% of DRN-NAc projection neurons are serotonergic. In coronal slices that include the DRN, whole cell recordings were conducted on neurons identified by fluorescent backlabeling from NAc or randomly selected within the nucleus. Nicotine increased action potential firing rates in a subset of DRN neurons. Voltage-clamp recording revealed nicotinic acetylcholine receptor (nAChR)-mediated inward currents that contribute to the nicotine-induced excitation. Nicotinic receptors also indirectly affect excitability by modulating synaptic inputs to these neurons. Nicotine enhanced excitatory glutamatergic inputs to a subset of DRN-NAc projection neurons, while inhibitory γ-aminobutyric acid (GABA)ergic inputs were modulated either positively or negatively in a subset of these neurons. The net effect of nAChR activation is enhancement of serotonergic output from DRN to the NAc, which may contribute to the effects of nicotine on mood and affect.

Determinants of consistent condom use vary by partner type among young men in Kisumu, Kenya: a multi-level data analysis.

To evaluate whether determinants of consistent condom use vary by partner type among young sexually active Kenyan men, we conducted a cross-sectional assessment of lifetime sexual histories from a sub-sample of men enrolled in a clinical trial of male circumcision. 7913 partnerships of 1370 men were analyzed. 262 men (19%) reported never, 1018 (74%) sometimes and 92 (7%) always using a condom with their partners. Condoms were always used in 2672 (34%) of the total relationships-212 (70%) of the relationships with sex workers, 1643 (40%) of the casual and 817 (23%) of the regular/marital relationships. Factors influencing condom use varied significantly by partner type, suggesting that HIV prevention messages promoting condom use with higher-risk partners have achieved a moderate level of acceptance. However, in populations of young, single men in generalized epidemic settings, interventions should promote consistent condom use in all sexual encounters, independently of partner type and characteristics.

Interleukin-15 and the regulation of lymphoid homeostasis.

Interleukin-15 (IL-15) is a cytokine that plays unique roles in both innate and adaptive immune cell homeostasis. While early studies suggested that IL-15 resembled IL-2, more recent work suggests that IL-15 may play multiple unique roles in immune homeostasis befitting its pleiotropic expression pattern. This review will focus on recent studies that highlight some of these functions.