Opiate abuse is a risk factor for human immunodeficiency virus (
HIV) infection. Because the direct effects of
opiates on
HIV infection are difficult to determine epidemiologically, animal models of
lentivirus infection are relied upon to study the effects of
opiates in the absence of confounding factors.
Morphine, the predominant metabolite of
heroin, is used in most experimental systems examining
heroin abuse. In this study,
morphine treatment of feline immunodeficiency virus (FIV)-infected cats modeled a typical pattern of escalating
drug use interspersed with withdrawals. Plasma
cortisol levels were measured for evidence of stress associated with
morphine withdrawal. In the
morphine-treated cats,
cortisol levels peaked at time points corresponding to
morphine withdrawal and returned to baseline levels during treatment and several weeks after the final withdrawal.
Morphine-treated cats displayed clear behavioral and physical signs of
opiate exposure and evidence of withdrawal when the
drug was stopped.
Morphine-exposed cats did not experience enhanced severity of FIV-related disease; in fact,
morphine demonstrated a protective effect on FIV-associated changes in brainstem auditory evoked potentials. Our research suggests that
opiate exposure is unlikely to adversely affect the progression of acute
lentivirus infection and might be beneficial in controlling associated neurological disease.