Alpha 1 adrenoceptors Site: postsynaptic in the effector tissues
- Generalized vasoconstriction of (more than epinephrine 40 times, & result in retention salt water) all blood vessels (arteries and veins) causing hypertension.Z
- Contraction of pupillary dilator muscle causing mydriasis.
- Contraction of gut sphincters
- Contraction of trigone and sphincter of urinary bladder.
- Contraction of the uterus.??????????????
- Ejaculation.
- Contraction of the pilomotor muscle causing hair erection.
- Adrenergic sweating e.g. in palms of hands.Z
- Increase neuromuscular junction (NMJ) impulse transmission.
Usually contraindicated in cold flu medication for Hypertension patients due containing Alpha 1 adrenoceptors - may lead to 2ry hypertension with decongenants
Alpha 2 adrenoceptors
Site: Presynaptic and Postsynaptic.
Generally antagonising effect of Alpha 1
Presynaptic alpha 2: Decrease NE and AC.CH release (feedback or autoregulation).
Postsynaptic alpha 2:
- CNS (decrease central sympathetic outflow)
- Decreased renin
- So, it decrease central & peripheral sympathetic discharge
- Any drug having alpha 2 stimulant action will produce all the above mentioned effects.