Intranasal Administration of Neuropeptide Y in Healthy Male Volunteers

There is growing evidence that neuropeptides, including neuropeptide Y (NPY), act as neuronal messengers in the brain and have diverse neurobehavioral functions. Their therapeutic application for psychiatric disorders has been limited, however, by difficult and unreliable penetration of the blood-brain barrier (BBB). The BBB has prevented the use of many therapeutic agents for treating central nervous system (CNS) disorders. Several molecules have successfully been administered through intranasal delivery, however, thanks to the unique connection that the nerves involved in sensing odors and chemicals provide between the CNS and its environment.

NPY, the most abundant peptide in the mammalian brain, is co-localized with norepinephrine in sympathetic nerve fibers and has been of longstanding interest to our research group (Morgan et al., 2002; Morgan et al., 2003; Morgan et al., 2001; Morgan et al., 2000; Rasmusson et al., 2000; Rasmusson et al., 1998) because of its potential role in modulating mood and anxiety. NPY has been implicated as factor in the adaptive stress response (Thorsell et al., 1999), and has been shown to impact the consolidation of fear-related memories after shock (Flood et al., 1989). Clinically, lower plasma NPY levels have been correlated with greater psychological distress, increased symptoms of dissociation, and poorer performance among active duty military personnel. Acute stress in humans has been found to elicit NPY release, in a manner parallel to the changes in cortisol and norepinephrine that are usually seen, with a blunting of the plasma NPY response in response to yohimbine (Morgan et al., 2002). Baseline NPY levels in combat veterans with PTSD are reduced compared to healthy non-traumatized individuals (Rasmusson et al., 2000). Another study found that repeated exposure to traumatic stress, rather than the presence of PTSD or PTSD-type symptoms, is associated with a reduction in baseline plasma NPY (Morgan et al., 2003). A recent report found deceased CSF concentrations of NPY in patients with treatment resistant unipolar major depression (Heilig et al 2004). In summary, there has been suggestion from studies in patients with anxiety and mood disorders as well as healthy volunteers of an abnormal regulation of this peptide.

In this study, we will evaluate intranasal administration of NPY in healthy male volunteers ages 25-45 using a specialized delivery device. Pending the initial feasibility and tolerability in healthy volunteers, future protocols will examine the effect of intranasal NPY administration in patients with disorders such as PTSD, major depression, panic disorder, and social anxiety disorder.