M06.16.002 Dopamine Receptors

Written by

in

Learning Objectives

By the end of this session, the learner will be able to differentiate between D1-like and D2-like receptors, describe the pathophysiology of Parkinson’s disease, and recognize the clinical hallmark signs of dopaminergic depletion.

1. Dopamine Receptor Subtypes

Dopamine receptors are categorized into two families based on their G-protein coupling and downstream effects on Adenylyl Cyclase.

Receptor Family Coupling Subtypes & Locations
D1-like G_s coupled (Stimulatory) D_1 and D_5
D2-like G_i coupled (Inhibitory) D_2, D_3, D_4

2. Specific D_2 Receptor Clinical Focus

The D_2 receptor family is subdivided based on the specific pathways they modulate, which is critical for understanding drug side effects.

Receptor Subtype Location/Pathway Significance
D_{2A} Nigrostriatal Involved in motor control and EPS side effects.
D_{2C} Mesolimbic Involved in reward, emotion, and psychosis.

3. Parkinson’s Disease Pathophysiology

Parkinson’s disease is characterized by a loss of dopaminergic neurons in the Substantia Nigra pars compacta.

Feature Biochemical Status Physiological Result
Dopamine Decreased Loss of inhibition in the striatum.
Acetylcholine (ACh) Relatively Increased Excessive excitatory signaling in motor pathways.

Clinical Pearls: The “TRAP” Symptoms

Remember the classic signs of Parkinson’s using the mnemonic TRAP:

  • T – Tremor: “Pill-rolling” resting tremor (improves with intent).
  • R – Rigidity: “Cogwheel” stiffness in the limbs.
  • A – Akinesia / Bradykinesia: Slowness of movement; masked facies.
  • P – Postural Instability: Frequent falls and a shuffling gait.

Check Your Knowledge: