Neurotransmitter Identification and Proof of Function

Flashcards about Neurotransmitter Identification and Function

What key concepts should students understand after the lecture?

Criteria used to establish a chemical substance as a neurotransmitter, the establishment of noradrenaline, and the importance of identifying neurotransmission systems for pharmacologists.

What are some established neurotransmitters?

Acetylcholine, noradrenaline, dopamine, glutamate, GABA, glycine, substance P, vasoactive intestinal peptide, adenosine triphosphate, and nitric oxide.

What are some putative neurotransmitters?

Histamine, adenosine, taurine, urotensin II, angiotensin I, carbon monoxide, and hydrogen sulphide.

What are the usual steps towards establishing a neurotransmitter?

Identification of biological activity of tissue extract, identification of active principle, identification of physiological roles, and satisfying the 7 criteria for a neurotransmitter.

What biological activity was found in aqueous extracts of adrenal glands by Oliver & Schafer (1895)?

The extract increased the rate and force of contraction of the frog isolated heart and increased blood pressure of the anaesthetized dog.

Who identified ‘epinephrine’ and ‘adrenaline’ and when?

Abel (USA) identified ‘epinephrine’ in 1898, and Takamine (UK) identified ‘adrenaline’ in 1901.

What did Langley find in 1901 regarding adrenal extract?

Langley noted that the effects of adrenal extract are similar to those of sympathetic nerve activation in 1901.

What did Elliott propose in 1905 regarding adrenaline?

Elliott suggested adrenaline mimics the effects of sympathetic nerves and may be the sympathetic transmitter in 1905.

According to Barger & Dale (1910), how did adrenaline and noradrenaline differ in their effects on piloerection and bladder relaxation?

Piloerection showed strong response with sympathetic nerve stimulation and adrenaline but weak with noradrenaline. Bladder relaxation showed weak response with adrenaline but strong with noradrenaline.

What did fluorescence spectroscopy reveal about sympathetic nerves between 1960-64?

Fluorescence spectroscopy showed sympathetic nerves release noradrenaline.

What is usually required in identifying the presence of a neurotransmitter?

Histology or identification of its enzymes, with the removal by denervation of the putative transmitter.

What are the key enzymes involved in noradrenaline synthesis in the nerve?

Tyrosine hydroxylase and dopa decarboxylase.

What enzyme is notably absent in the nerve regarding noradrenaline synthesis?

There is no phenylethanolamine-N-methyl transferase in the nerve.

What is the purpose of storage vesicles for noradrenaline in the nerve?

Storage vesicles concentrate and protect the transmitter from degradation and release the concentrated transmitter into the synaptic gap quickly.

Who used the rabbit jejunum to study the release of noradrenaline from the nerve?

Finkleman (1930) used the rabbit jejunum to study it.

What was Ahlquist's contribution to understanding noradrenaline receptors in 1948?

Based on agonist potency ratios, Ahlquist proposed the existence of distinct receptors (alpha & beta) in 1948.

What evidence validated Ahlquist's concept of distinct receptors?

Differing antagonist affinities, radioligand binding affinities, transduction mechanisms and molecular biology.

How is noradrenaline swiftly inactivated after its action?

Noradrenaline is inactivated by uptake via transporter proteins into either the nerve or the effector cell (neuronal uptake/uptake-1).

What are the key criteria that establish noradrenaline as a neurotransmitter?

Mimics nerve, presence in nerve, synthesis in nerve, storage in nerve, release, specific receptors, and ceases action fast.

Why is it important to identify transmitters?

Understanding disease mechanisms and developing selective drugs as therapeutic agents.