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RATIONALE Prepulse inhibition (PPI) of the startle reflex occurs when brief, non-startling tactile, acoustic or visual stimuli are presented 20-500 ms before the startling stimulus. OBJECTIVE To review information about PPI-mediating brain stem circuits and transmitters, and their functions. RESULTS Midbrain systems are most critical for the fast relay(More)
The startle reflex is elicited by intense tactile, acoustic or vestibular stimuli. Fast mechanoreceptors in each modality can respond to skin or head displacement. In each modality, stimulation of cranial nerves or primary sensory nuclei evokes startle-like responses. The most sensitive sites in rats are found in the ventral spinal trigeminal pathway,(More)
Quantitative properties of the neural system mediating the rewarding and priming effects of medial forebrain bundle (MFB) stimulation in the rat have been determined by experiments that trade one parameter of the electrical stimulus against another. The first-order neurons in this substrate are for the most part long, thin, myelinated axons, coursing in the(More)
Cholinergic neurons of the pedunculopontine tegmental nucleus (Ch5) and laterodorsal tegmental nucleus (Ch6) monosynaptically activate dopamine neurons of the substantia nigra and ventral tegmental area (VTA) via nicotinic and muscarinic receptors. The nicotinic receptors near the VTA have been proposed to be important for nicotine self-administration in(More)
Rats lever pressed for concurrent electrical stimulation of the lateral hypothalamus and ventral tegmentum. The pulse-pair stimulation technique was used, with the first pulse of each pair applied to one electrode and the second to the other electrode; the intrapair interval was varied. The effectiveness of stimulation, measured behaviorally, increased(More)
Paired-pulse stimulation methods have been used in many studies to measure the excitability properties of the directly stimulated neurons mediating stimulation-elicited behaviors. In this article those methods are evaluated quantitatively. The most frequently used method, in which rate of behavior is measured as a function of conditioning-test (C-T)(More)
Circadian rhythms in rodents respond to arousing, nonphotic stimuli that contribute to daily patterns of entrainment. To examine whether the motivational significance of a stimulus is important for eliciting nonphotic circadian phase shirts in Syrian hamsters (Mesocricetus auratus), the authors compared responses to a highly rewarding stimulus (lateral(More)
Cholinergic neurons of the pedunculopontine nucleus (Ch5) and laterodorsal tegmental nucleus (Ch6) monosynaptically activate dopamine neurons of the substantia nigra, zona compacta (A9), and ventral tegmental area (A10) via muscarinic and nicotinic receptors. Ch5 cells and Ch6 cells are inhibited by local injections of muscarinic agonists, suggesting the(More)
Rats were implanted with stimulating electrodes in the lateral hypothalamus, and cannulae for chemical injections in the ventral tegmentum. Injections of atropine, a muscarinic antagonist, increased thresholds for self-stimulation in a dose-dependent fashion, without slowing bar pressing rates. Thresholds increased less for a self-stimulation site(More)