The acoustic startle reflex is an automatic and involuntary response that occurs in humans and other animals when they are exposed to sudden and intense acoustic stimuli, such as loud noises. This response can be influenced by several factors, including the intensity and timing of the stimulus, the individual's state of alertness, and contextual factors. It can also be modulated by prior exposure to a weak prepulse shortly before the startling stimulus, a phenomenon known as prepulse inhibition (PPI). PPI reflects the brain's ability to filter out irrelevant or non-threatening sensory information, and is considered an important indicator of sensorimotor gating. In individuals with schizophrenia, both the startle response and prepulse inhibition are disrupted, which is believed to result from alterations in glutamatergic and dopaminergic neurotransmission. These deficits in sensorimotor gating may lead to sensory overload and the misinterpretation of sensory information. Here we describe a protocol to measure PPI in mice and rats using a startle chamber from Insight®️ (SP, Brazil).