Autoreceptors, definition

As previously noted, all currently available antidepressants enhance monoamine neurotransmission by one of several mechanisms. The most common mechanism is inhibition of the activity of SERT, NET, or both monoamine transporters (Table 30-2). Antidepressants that inhibit SERT, NET, or both include the SSRIs and SNRIs (by definition), and the TCAs. Another mechanism for increasing the availability of monoamines is inhibition of their enzymatic degradation (the MAOIs). Additional strategies for enhancing monoamine tone include binding presynaptic autoreceptors (mirtazapine) or specific postsynaptic receptors (5-HT antagonists and mirtazapine). Ultimately, the increased availability of monoamines for... 

Like presynaptic dopamine autoreceptors, presynaptic histamine autoreceptors are activated by the released endogenous transmitter to inhibit further histamine release, as shown by the increase in histamine release caused by antagonists at H3 receptors a definite piece of physiology. Evidence has been presented recently that cardiac postganglionic sympathetic neurons of the guinea pig synthesize and release histamine as a co-transmitter (Li et al. 2003 2006). These noradrenaline-histamine neurons possess H3 autoreceptors which, when activated, depress the release of both noradrenaline and histamine - unlike the D2-like autoreceptors of dopamine-neurotensin neurons which modulate the release of the two cotransmitters in opposite direction (see Section 2.2). It would be of interest to see whether, conversely, activation of ot2-autoreceptors inhibits the release of histamine in the guinea pig heart. 

Hamon s anti-5-HT1A antibodies have been used successfully by several laboratories to immunolocalize 5-HT1A receptors at the light microscopic level in the rat CNS (14,15,25-30). One of these studies has definitely proven that 5-HT1A receptors are autoreceptors by showing their presence on cell bodies... 

The majority of these compounds are agonists or partial agonists. Pure antagonists, devoid of any agonistic activity at presynaptic receptors (somatodendritic autoreceptors) or postsynaptic receptors were identified only very recently (for details of the definition of agonists, partial agonists and antagonists, see [6]). 

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