Postnatal development of cardiac and respiratory control following prenatal drug exposure

Of primary importance in the consideration of animal models of prenatal drug exposure is the recognition of interdependence among physiologic systems, the pervading influence of sleep and waking states, and the potential interaction between drug-induced structural changes and physiologic function. It is difficult for a drug effect on the cardiovascular system not to modify respiratory pattern; any change in blood pressure, systemic perfusion, or heart rate is immediately reflected in breathing; respiratory pattern, in turn, through negative thoracic pressure and other sensory activity, can alter cardiac patterning. The respiratory system itself is one component of a somatic motor system, and neural motor control structures undergo substantial modification by drug action. Enhancing or diminishing any aspect of interaction is the influence of sleep states, which nonlinearly can alter relationships between physiologic systems, occasionally dissociating systems, as in the case of temperature effects on breathing during REM sleep. Finally, drug-induced structural changes that alter morphology of the upper airway can result in obstructive respiratory events, leading to pronounced cardiovascular sequelae.