Pharmacology of Histamine , Histamine receptors and Anti-histamine Drugs : Part 2
Вставка
- Опубліковано 28 вер 2018
- 📌 𝐅𝐨𝐥𝐥𝐨𝐰 𝐨𝐧 𝐈𝐧𝐬𝐭𝐚𝐠𝐫𝐚𝐦:- / drgbhanuprakash
📌𝗝𝗼𝗶𝗻 𝗢𝘂𝗿 𝗧𝗲𝗹𝗲𝗴𝗿𝗮𝗺 𝗖𝗵𝗮𝗻𝗻𝗲𝗹 𝗛𝗲𝗿𝗲:- t.me/bhanuprakashdr
📌𝗦𝘂𝗯𝘀𝗰𝗿𝗶𝗯𝗲 𝗧𝗼 𝗠𝘆 𝗠𝗮𝗶𝗹𝗶𝗻𝗴 𝗟𝗶𝘀𝘁:- linktr.ee/DrGBhanuprakash
Histamine is a chemical mediator that plays a key role in various physiological processes in the body. It is involved in allergic reactions, regulation of gastric acid secretion, neurotransmission, and immune responses. Histamine exerts its effects by binding to specific receptors, known as histamine receptors, which are present on various cells and tissues throughout the body.
Histamine Receptors:
There are four main subtypes of histamine receptors, designated as H1, H2, H3, and H4 receptors. Each receptor subtype is found in different locations and serves different functions:
H1 Receptors: These receptors are primarily located on smooth muscle cells, endothelial cells, and nerve endings. Activation of H1 receptors leads to smooth muscle contraction, increased vascular permeability, itching, and bronchoconstriction. Antagonists of H1 receptors are commonly used as anti-allergic drugs.
H2 Receptors: H2 receptors are predominantly found in the stomach, where their activation stimulates the secretion of gastric acid. Antagonists of H2 receptors, known as H2 blockers, are used to reduce gastric acid secretion and are commonly used in the treatment of gastric ulcers and gastroesophageal reflux disease (GERD).
H3 Receptors: These receptors are mainly located in the central nervous system, particularly in areas involved in neurotransmission. H3 receptors act as autoreceptors and heteroreceptors, regulating the release of various neurotransmitters, including histamine itself. Modulation of H3 receptors is being explored for the treatment of conditions such as Alzheimer's disease, attention deficit hyperactivity disorder (ADHD), and sleep disorders.
H4 Receptors: H4 receptors are primarily expressed on immune cells, such as mast cells, eosinophils, and T cells. Activation of H4 receptors contributes to immune responses, including chemotaxis and cytokine release. H4 receptor antagonists are being investigated for their potential role in the treatment of inflammatory and allergic disorders.
Anti-Histamine Drugs:
Antihistamines are medications that block the effects of histamine by binding to and inhibiting histamine receptors. They are widely used to relieve symptoms associated with allergic reactions, such as sneezing, itching, runny nose, and hives.
Antihistamines can be classified into two generations:
First-Generation Antihistamines: These drugs, such as diphenhydramine and chlorpheniramine, readily cross the blood-brain barrier, leading to sedative effects. They are effective in alleviating allergic symptoms but are associated with drowsiness and other side effects.
Second-Generation Antihistamines: This group includes drugs such as cetirizine, loratadine, and fexofenadine. Second-generation antihistamines are less likely to cause sedation because they have reduced penetration into the central nervous system. They provide long-lasting relief from allergy symptoms and are generally preferred over first-generation antihistamines.
#pharmacology #pharmacologyvideos #pharmacologyusmle #pharmacologynext #medicalstudents #fmge #medicalcollege #nationalexittest #nationalexitexam #neetpg #mbbslectures #usmleprep #usmlestep1 #pharma
Sir I am so grateful that you exist!! Thank you so much :)
Im a mexican and I totally get your videos. Congrats!! Such a Good teacher
Veru neat explanation
Awesome sir
Nice explanation
thank u sir
Sil please make video about structure of adrenergic drugs
Interesting science and are the
H1 receptors, on hearth coronary blood vessels or cardiac smooth muscle only ??
Nice
Sir, I have a doubt, you said that in the previous video that the smooth muscles are relaxed by histamine and cause fall in BP, but here the same histamine acts on the visceral smooth muscles to cause broncho constriction.. both are smooth muscles rt, so how it's causing relaxation and constriction at the same time ?
That was smooth muscle component of the blood vessels
Thanks a lot , superb videos 🙏🙏🙏🙏🙏
Most welcome 😊
Nice click
Sir please organise the content.
It becomes very hard to make notes
Histamine increases heart rate and contractility
Thanks.
You're welcome
According to your last video ( part one of histamine) H1 present on smooth muscle and endothelium only then how does it acts on heart via H1 receptor
They are also present in heart
Sir Where is the part 4 of this series??
Basic of neet pg
Sir whats H3 receptor
Why does histamine act on H2 on blood vessels and cause their relaxation, whereas acts on heart to increase contraction?
@vinit bhargav kha se aate hai aise log
Because in vascular smooth muscles , increased Camp level causes activation of myosin light chain phosphorylase which is responsible for muscle relaxation and hence vasodilation whereas in heart and Skeletal muscles increased Camp causes activation of myosin light chain kinases which causes muscular contraction
Thanks sir
Sir histamine act on h2 receptor then sir decrease nhi krega gastric secretion ko
No
good sir. but little bit fast will be gud.
you can increase the speed yourself
In GIT, does histamine cause release of gastrin or direct HCl???
it increase the secretion of Hcl or gastric acid from parietal cells of stomach
Revision at: 6:30
Sir why antihistaminic drug avoid in asthma patient whereas histamine cause bronchocontraction
because the main mediator in bronchial asthma is leukotriens
and the histamine has insignficant role
because antihistamine drugs are histamine competitive antagonists, so they bind to H1 receptors found on branchial smooth muscle , but do not activate it , meaning block the action of histamine