5 anxiety disorders

PHARMACOLOGY 29mitter. When a molecule of the neurotransmitter binds an autoreceptor, itproduces a negative feedback effect that causes the nerve cell to decreasefurther neurotransmitter release. Consequently, blocking the autoreceptor promotesneurotransmission by eliminating this negative feedback mechanism.The antidepressant mirtazapine (Remeron) acts in part by this mechanism.4. Stimulating Postsynaptic Receptors. Neurotransmitters carry their signals bydiffusing across the synapse from the axon terminals to receptors on theneighboring, so-called postsynaptic, nerve cell. Some medications stimulatepostsynaptic receptors and thereby act by mimicking the action of theneurotransmitter itself.5. Neurotransmitter Precursors. Most neurotransmitters are manufactured bythe neurons themselves from a variety of simple building block substancesthat are commonly obtained from the diet. Another way to promote neurotransmissionis to increase the available pool of neurotransmitter by supplementingthe supply of a precursor substance. In most instances, this is a veryinefficient and largely ineffective approach to treatment. However, L-DOPA,the immediate precursor to the neurotransmitter dopamine, remains an effectivetreatment for Parkinson’s disease.6. Stimulating Neurotransmitter Release. Psychostimulants, such as methylphenidate(Ritalin), can directly trigger the release of certain neurotransmitters(e.g., dopamine and norepinephrine) from the neuron’s axon terminal.Psychiatric medications can also act by decreasing neurotransmission in certaincircuits either by directly blocking postsynaptic receptors or by increasing therelease of inhibitory neurotransmitter substances. When a medication acts by blockingpostsynaptic receptors, no matter how much neurotransmitter is released fromthe axon terminal, the signal cannot be transduced to the neighboring cell if thepostsynaptic receptors are blocked. Medications that act by blocking postsynapticreceptors include nefazodone (Serzone), an antidepressant that acts primarilyby blocking a certain class of serotonin receptors, and antipsychotics, which actby blocking one or more classes of dopamine and/or serotonin postsynapticreceptors.2.4.4 Predicting Medication EffectsEvery medication exerts multiple effects. The effect for which it is prescribed iscalled the therapeutic effect. All other effects are side effects. Which of these effectsis the therapeutic one is therefore determined when the decision is made to take themedication.An example is obviously in order. Medications that block the neurotransmissionof histamine (i.e., antihistamines) produce several effects including drowsiness,drying of nasal passages, and weight gain. If the common over-the-counter antihistaminediphenhydramine (Benadryl) is prescribed to help a patient who has insomnia,then drowsiness is the therapeutic effect. Weight gain and dried nasal passages