Hyper-Arousal in Chronic Primary Insomnia

Inclusion Criteria for Insomniacs: * Men and women with primary insomnia of at least 3 months in duration * ages 21-65 years old * BMI \<35 kg/m2 to enable microneurography * Moderate to severe insomnia based on the Insomnia Severity Index (ISI) questionnaire * Pittsburgh Sleep Quality Index (PSQI) \> 5 * Self-reported habitual sleep duration \< 6.5 hours Inclusion criteria for good sleepers: * 21-65 years old men and women with BMI \<35 kg/m2 * No insomnia based on ISI questionnaire * Self-reported habitual sleep duration ≥ 6.5 hours but \< 9 hours * PSQI\<5 * Sleep efficiency on PSG with TRT of 8 hours \> 85% * No history of mental illness, shift work, circadian rhythm disorders Exclusion criteria for both insomniacs and good sleepers: * Sleep disorders other than insomnia as assessed by screening PSG (apnea-hypopnea index or AHI ≥ 10, PLM arousal index ≥ 5) * Circadian rhythm sleep disorders * Diabetic based on HbA1c ≥ 6.5 %. For those with HbA1c ≥ 6.0 but \<6.5%, the non-diabetic condition will be confirmed by 2-h oral glucose tolerance test * History of meeting DSM-IVR criteria based on the Mini International Neuropsychiatric Interview version 6.0 for any major psychiatric disorder * Unstable or serious medical conditions * Current, or use within the past month, of psychoactive (other than stable treatment with antidepressants), hypnotic, stimulant or analgesic medications (except occasional non-narcotic analgesics), beta blockers or alpha blockers * Shift work or other types of self imposed irregular sleep schedules * Habitual smoking * Habitual alcohol consumption * Pregnancy