Nervous System Drugs and Neurotransmitters

Nervous System Drugs

• Nervous system drugs affect the central and peripheral nervous systems.
• These drugs influence neurotransmitters and/or their receptors.
• The CNS is the brain and spinal cord, and the PNS includes cranial and spinal nerves, plus ganglia.
• Nervous system functioning is vital for maintaining internal homeostasis.
• Communication happens via electrical impulses along nerves, informing the CNS and PNS about stimuli, and eliciting an appropriate response.
• Neurons are the functional cells.
• Dendrites receive messages.
• Axons carry messages away from the cell body.
• Sensory neurons (afferent) transmit impulses toward the CNS; motor neurons (efferent) carry them away.
• Neurotransmitters allow communication between neurons.

Neurotransmitters

• Neurotransmitters are chemical substances facilitating impulse transfer between neurons.
• They bind to receptor sites on the receiving neuron.
• Drugs can either block neurotransmitter effects (lytic) or mimic their effects (mimetic).

Peripheral and Autonomic Nervous Systems

• The Peripheral Nervous System (PNS) has afferent and efferent nerves.
• The Autonomic Nervous System (ANS) is involuntary and controlled by the sympathetic and parasympathetic branches.
• The sympathetic nervous system (SNS) is the “fight or flight” response.
• The parasympathetic nervous system (PNS) is the “rest and digest” response.

Nervous System Receptors

• Alpha and Beta receptors play vital roles in the sympathetic nervous system.
• Muscarinic and nicotinic receptors are present in the parasympathetic nervous system.
• These receptors determine a drug's action.

Inhalant Anesthetics

• Inhaled anesthetics enter through the lungs (respiration).
• They're distributed to tissues by blood circulation.
• The exact mechanism of action is unknown but may involve GABA neurotransmitters.
• Inhaled anesthetics often cross the blood-brain barrier for effect.
• Anesthetic depth depends on the concentration in the brain and alveoli.
• Concentration gradients drive the delivery process.
• Maintaining proper vaporizer settings is vital for smooth anesthesia.
• Inhalant anesthetics have several adverse effects, including respiratory depression, cardiac depression, decreased blood pressure, etc.

Local Anesthetics

• Used for procedures that don't necessitate general anesthesia.
• Nerve blocks can be done to limit pain transmission.
• Some examples of topical anesthetics are bupivacaine, lidocaine, mepivacaine, prilocaine, proparacaine.

Other Anesthetic Drugs

• Different classes of anesthetic drugs exist, like phenothiazines, benzodiazepines, alpha-2 agonists, barbiturates, dissociatives, opioids, and non-classified anesthetics.
• Some general uses and precautions for these drugs are described.
• Some drugs have different trade names.
• Drug cocktails provide more comprehensive outcomes.

Behavioral Medications

• Used for various behavioral issues in animals, like fear, anxiety, and compulsive behaviors.
• Behavior modification, training, and medication are often combined for optimal outcomes.
• Medication effectiveness can take weeks but should not be stopped abruptly.