Pharmacology – I (Practical)

[PHL 313]

Lab – 1:

Different Laboratory Animals and Their Application

• PHARMACOLOGY is the branch of science which deals with study of drugs on living

systems

• EXPERIMENTAL PHARMACOLOGY: deals with study of effect of various

Pharmacological agents on different animal species

• AIMS :

▫ To find out the therapeutic agent suitable for human use

▫ To study the toxicity of the drugs

▫ To study the mechanism and site of action of drugs

PHARMACOLOGY

Discovery of new drugs or to study the actions of existing drugs

Preclinical Clinical

Two ways Phase -1,2,3,4

• Intact animal study – invivo

• Isolated organ study – invitro

Clinical Trial

Phase I: • A small group (20-100) of healthy volunteers • The safety, tolerability, pharmacokinetics, and

pharmacodynamics of a drug • These trials are often conducted in an inpatient clinic,

where the subject can be observed by full-time staff • Pay ranges from a small amount of money for a short

period of residence, to a larger amount of up to approx $6000 depending on length of participation.

Phase II: • Safety assessments in a larger group of healthy

volunteers and patients (20-300)

Phase III:

• Randomized controlled multicenter trials on large patient groups (300–3,000 or more depending upon the disease/medical condition studied)

• Phase III trials are the most expensive, time-consuming and difficult to design and run, especially in therapies for chronic medical conditions

Phase IV:

• Is also known as Post Marketing Surveillance Trial.

• Harmful effects discovered by Phase IV trials may result in a drug being no longer sold, or restricted to certain uses

• Experimental pharmacology – great importance

• Experimenter should take outmost care

• Sacrificing – human

• Euthanasia – painless killing

• Laboratory animals – breaded and handled in laboratory

▫ Rat

▫ Mice

▫ Guinea pig

▫ Rabbits

▫ Frogs

▫ Other: Cat, Dog, Monkey, Pigeon etc.

RATS • Species – Rattus norvegicus

• Albino rats of Wistar strain are commonly used

• Other strains –

▫ Wistar kyoto rat

▫ Sprague Dawley rat

▫ Biobreeding (BBDP) rat

▫ Long-Evans rat

▫ Zucker rat Genetically modified rats

▫ Hairless rats (Rowett nude, Fuzzy, Shorn)

▫ RCS rats

Wistar rat

• Wistar rats are strain of albino rats belonging to the species Rattus norvegicus. • This strain was developed at the Wistar Institute in 1906

for use in biological and medical research, and is notably the first rat strain developed to serve as a model organism at a time when laboratories primarily used Mus musculus, or the common House mouse.

• The Wistar rat is currently one of the most popular strains used for laboratory research.

• It is characterized by its wide head, long ears, and having a tail length that is always less than its body length.

• The Sprague Dawley rat and Long-Evans rat strains were developed from Wistar rats. Wistar rats are more active than other strains like Sprague Dawley rats.

Sprague Dawley rat

• The Sprague Dawley rat is multipurpose breed of albino rat used extensively in medical research.

• Its main advantage is its calmness and ease of handling.

• The adult body weight is 250–300g for females, and 450–520g for males. The typical life span is 2.5–3.5 years. These rats typically have increased tail to body length ratio compared with Wistar rats.

Biobreeding rat

• Biobreeding Diabetes Prone rats (or BBDP rat) are inbred rat strain that spontaneously develops autoimmune Type 1 Diabetes.

• BB rats are used as an animal model for Type 1 diabetes.

• The strain re-capitulates many of the features of human type 1 diabetes, and has contributed greatly to the research of T1D pathogenesis

Long-Evans rat

• Long-Evans rats are strain of rats belonging to the species Rattus norvegicus.

• This strain was developed by Drs. Long and Evans in 1915 by crossing several Wistar females with a wild gray male.

• Long Evans rats are white with a black hood, or occasionally white with a brown hood.

• They are utilized as a multipurpose model organism, frequently in behavioral and obesity research.

Zucker rat

• Zucker rats were bred to be a genetic model for research on obesity and hypertension.

• There are two types of Zucker rat: a lean Zucker rat; and the characteristically obese (or fatty) Zucker rat, capable of weighing up to 1 kilogram (2.2 lb)—more than twice the average weight.

• Obese Zucker rats have high levels of lipids and cholesterol in their blood, and gain weight from an increase in both the size and number of fat cells.

• Obesity in Zucker rats is primarily linked to their hyperphagic nature, an excessive hunger.

Hairless rats

• Hairless rats provide researchers with valuable data regarding compromised immune systems and genetic kidney diseases.

• The more common ones are denoted as rnu (Rowett nude), fz (fuzzy), and shn (shorn).

• Rowett nudes, first identified in 1953 in Scotland, have no thymus. The lack of this organ severely compromises their immune system, infections of the respiratory tract and eye increasing the most dramatically.

• Fuzzy rats were identified in 1976. The leading cause of death among these rats is a progressive kidney failure.

• Shorn rats were bred from Sprague Dawley rats in 1998. They also suffer from severe kidney problems.

RCS rats • The Royal College of Surgeons (RCS) rat is the

first known animal with inherited retinal degeneration.

ADVANTAGES AND CHARACTERISTICS:

▫ small in size

▫ drug to be tested required in small quantity

▫ vomiting center is absent – oral administration can be done

▫ gall bladder and tonsils are absent

Continuous flow of bile into intestine, This facilitates the

study of the drugs acting on bile, cholesterol reabsorption etc.

▫ In stomach, fundus and pyloric parts have clear lining

between them

▫ Gastric acid secretion is continuous

EXPERIMENTAL USE: (Adult weight: 200-250g, Age: 1.5 months)

▫ Psychopharmacological studies

▫ Study of analgesics and anticonvulsants

▫ Bioassay of various hormones, such as insulin, oxytocin, vasopressin

▫ Isolated tissue preparations like uterus, stomach, vas deferens, aortic strip, heart etc.

▫ Chronic study on blood pressure

▫ Gastric acid secretion studies

▫ Hepatotoxicity studies

▫ Acute and chronic toxicity studies

MICE ( Mus musculus) •Swiss albino mice are commonly used species

•Other strains are – Balb/C and C-57

ADVANTAGES AND CHARACTERISTICS:

▫ Smallest

▫ Less drug required

▫ Easy to handle

▫ Cheap

EXPERIMENTAL USES: (Adult weight: 20-25g, Age: 1 month)

▫ Toxicological studies specially acute and subacute toxicity

▫ Bioassay of insulin

▫ Screening of analgesic and anticonvulsant

▫ Screening of chemotherapeutic agents

▫ Studies related to genetics and cancer research

▫ Drugs action on CNS

GUINEA PIGS ( Cavia porcellus )

ADVANTAGES AND CHARACTERISTICS :

▫ Docile animals

▫ Highly susceptible to TB and anaphylaxis

▫ Highly sensitive to histamine, penicillin

▫ Required exogenous vitamin C in diet

EXPERIMENTAL USES (Adult weight: 400-600g, Age: 3 months)

▫ Evaluation of bronchodilators

▫ Study of histamine and antihistamines

▫ Bioassay of digitalis

▫ Evaluation of local anesthetics

▫ Hearing experiments because of sensitive cochlea

▫ Isolated tissues especially ileum, tracheal chain, heart etc.

▫ Study on TB and ascorbic acid metabolism

RABBITS (Lupas cuniculus) ADVANTAGES AND CHARACTERISTICS :

▫ Docile animal with large ears

▫ New Zealand white strains are widely used

▫ It has huge caceum and long appendix

▫ Enzyme atropine esterase is present in rabbit liver and plasma so it can

tolerate large doses of belladona (atropine)

EXPERIMENTAL USES (Adult weight: 1.5-3.0 Kg, Age: 5-6months)

▫ Pyrogen testing

▫ Bioassay of anti-diabetic, and sex hormones

▫ Drugs used in glaucoma

▫ Pharmacokinetic studies

▫ Studies related to antifertility agents

▫ Isolated preparations like heart, duodenum, ileum, etc.

▫ Study on local anaestetics

▫ Study on miotic and mydratics

FROGS (Rana tigrina)

ADVANTAGES AND CHARACTERISTICS :

▫ Used before 200 years

▫ Easily available during rainy season

▫ Amphibian animal and safe to handle

▫ Cannot breed in lab

EXPERIMENTAL USES

▫ Isolated preparations, rectus abdominis muscle & heart

▫ Drugs acting on CNS

▫ Drugs acting on NMJ

Housing & Maintenance of Laboratory animals

• Institutional or departmental ethical committee

• Animal House

Separate building at a quiet atmosphere, undisturbed by traffic

Should be hygienic & protected from extremes of climate

Good ventilation

Exhaust fan

Roof should be 10 feet high

Large no. of small rooms

Quarantine area

Extra space for office, surgery, washing and sterilizing, kitchen & incinerators

No overcrowding permitted

• Animal Cages:

Plastic, galvanised iron, aluminium etc.

Anodised aluminium is best

Size

Tray for food and water bottle

Bedding: rice husk or paper

Proper labeling

• Following requirements should be stressed on mind:

▫ Clean drinking water

▫ Ventilation

▫ Food

▫ Free movement

▫ Resting

▫ Temperature

▫ Humidity

▫ Diseases

▫ Handling

▫ Mental Health

Housing and Routine Care:

Animal Crowding

• Animal crowding in a cage affects environmental quality (the accumulation of urine, for example, leads to excess ammonia and moisture).

• Crowding can also cause newborn pups to be injured or killed. Crowding is a special concern for multiple litters in a cage since pups grow very quickly and rapidly increase their output of excreta.

• In particular, if the mother is about to give birth to a second litter, the first litter should be weaned and removed to new cages to prevent smothering and trauma of the newborns.

Routine Sanitation • Routine sanitation and environmental controls are necessary

for protecting animal health and for minimizing the introduction for non-experimental variables which could undermine the quality of research data.

• Sanitation schedules vary according to the type of mouse caging.

• Based on the types of caging and bedding in use at your facility, your institution will have a standard operating procedure (SOP) on the sanitation schedule for mouse cages.

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Quick Questions:

• Why do we need to use animals for research and teaching?

• What have people learned from animal research?

• Are the animals used in research & education protected and taken care of?

• Does everyone agree with using animals for research or do some people disagree?

Why Do We Need To Use Animals for

Research & Teaching?

• The functions of cells and organs are basically the same in animals and humans.

• Biologically, humans are in the Animal Kingdom.

• What we learn from animals: is useful in human and animal medicine.

Why Do We Need To Use Animals for

Research & Teaching? • Animal are used to: ▫ Understand how diseases

affect living tissue ▫ Develop and test treatments —

including treatments for animals

▫ Train future scientists and health-care professionals

Can Computer Models and Cell

Cultures Replace Animal Research?

• Non-animal models are very important, but have limitations. They cannot duplicate the complicated interactions in a whole system.

• Final testing depends on studies in living, whole animals or people.

This is actually required by federal law.

Can Results from Animal Studies Really

Be Applied to Humans?

• They CAN and ARE. Virtually all drugs, devices and medical procedures have been developed with some animal research.

This dog, Kodi, underwent hip replacement surgery twice. Hip replacement surgical techniques were tested first on animals and now help both animals and people.

Animal Use in Biomedical Research

Polio • Landsteiner and Popper proved it

infectious; able to transmit disease to monkeys.

• Salk and Sabin developed their vaccine through work with chickens and monkeys.

Polio was one of the most dreaded childhood diseases of the 20th century. Polio epidemics have crippled thousands of people, mostly young children;

the disease has caused paralysis and death for much of human history. Developed in the 1950s, polio vaccines are credited with reducing the

global number of polio cases per year from many hundreds of thousands to around a thousand.

Animal Use in Biomedical Research

• Infant Mortality ▫ Studies in sheep led to use of steroids in treatment of

respiratory distress syndrome, a major cause of death in premature infants.

▫ Advances in understanding and treatment of sudden infant death syndrome (SIDS) came from studies in rats, mice, dogs, and sheep.

Animal Use in Biomedical Research

• High Blood Pressure (HBP) ▫ Goldblatt linked HBP to kidneys in rats, cats, and dogs. This

research led to treatments for high blood pressure.

▫ Cushing linked HBP to brains in dogs. This research led to understanding the nervous system’s influence on blood pressure and development of drugs to treat it.

Animal Use in Biomedical Research

• Obesity

▫ Major risk factor for diabetes mellitus, high blood pressure, heart attack, stroke and certain cancers

▫ Epidemic in the United States: 64% of adults are overweight and 25% are obese

▫ Mouse models and Zucker obese rats are shedding new light on causes of overeating, importance of leptin receptors, and ways that obesity leads to disease.

Animal Welfare Act

• Includes rules for mandatory surprise inspections

of animal research facilities.

• These federal laws & regulations are in place to ensure that all research animals receive:

▫ Good veterinary care

▫ Appropriate housing

▫ Proper Feeding

▫ Humane handling

▫ Sound sanitation and ventilation

Working with the Laboratory Animals This tutorial is to provide information on the use of rats and mice in experiments. Acquisition of animals Acclimation Animal Handling and Restraint Sex Determination

We have to be cared for properly. It’s the law!!!!!!!

Acquisition of animals

• Animals not bred in the research facility are to be acquired lawfully.

• Researchers should make every effort to ensure that those responsible for transporting the animals to the facility provide adequate food, water, ventilation, space, and impose no unnecessary stress on the animals.

• Endangered species should be used only with full attention to required permits and ethical concerns.

Acclimation

• Upon arrival to your facility, your animals should have an acclimation period before they are used in research studies.

• This period of time allows animals to adapt to a new environment.

• Effects of transportation stress include alterations in various blood parameters, immune cell function, food intake, and animal behavior.

• The period of time necessary for biological stabilization will depend on the parameters to be studied.

• Refer to your institution's attending veterinarian for recommendations that are appropriate for your project. Typically, acclimation periods can range from days to over a week, depending on the studies involved.

Animal Handling and Restraint

It's important to remember the following: As a small animal, rats and mice can be easily injured if

handled roughly. You should learn how to handle them firmly but gently and with confidence to avoid injuring these delicate animals.

Rats and mice are inclined to become aggressive and bite. Although their teeth seldom break through your skin, a bite can hurt! Develop your confidence in handling animals by learning from an experienced mentor and practice hand restraint first on anesthetized animals.

The best way to remove a mouse that is hanging on to your finger is to train yourself to lower your hand back into its cage. Presented with a retreat to its home cage, the mouse will quickly jump off your finger.

Hand Restraint There are two common hand methods for restraining rats and mice. No matter how you will restrain the mouse, mice are picked up the following way:

Remove the cage top if they are housed in a filter-top cage.

Place the wire lid top sideways on top of the cage. Pick up a mouse by the tail (away from the tail tip)

and lift the mouse directly to the wire lid. You will find that the wire lid is a useful area to which the mouse will want to hang on with its front feet, allowing you the opportunity to reposition your grasp.

Points to remember:

When picking up a mouse –

• Pick up the tail at the middle, not the tip. A mouse does not need to be picked up at the base of the tail like a rat does, because the mouse is light and its weight will not damage its tail.

• If you need a place to briefly sort and hold your mice, say while you are rapidly administering injections to a cage of mice, each mouse can be placed on the wire lid after its injection. Mice will stay on their wire lid a short while if food blocks are present, due to their instincts for food. If you quickly make all your injections, all the mice can be treated without a mix-up of repeated or skipped administrations.

Laboratory Animal (Mouse) Handling

Technique

• Oral Feeding

• Sexing

Oral Feeding in Mouse • Gastric intubation ensures that all the material was

administered

• Feeding amount limited to 1% of body weight

Tools for Oral Feeding in Mouse

A 18 G stainless steel, ball tipped needle

a glove

Grasp the loose skin on the back of

the mouse and restrain it’s tail with

your ring finger and little finger.

Then, introduce the feeding tube

from the pharynx in to the

esophagus when the mouse is in

the act of swallowing.

Common complications associated with gastric intubation are

damage to the esophagus and administration of substance into

the trachea. Careful and gentle passage of the feeding needle

will greatly reduce these possibilities.

• Most often used for rodents

▫ Gavage tube attached to hypodermic syringe

• Hold animal in proper position

• Insert tube at approximately 45 degree angle

▫ Do not force tube

• Withdraw and start again if resistance is met while inserting the tube

Gastric

Intubation

(Gavage)

The anatomy picture

showed the position of the

feeding needle tip inside

the esophagus with the

heart and sternum

removed.

Determining Sex and Age • Refer to the image below: the top two mice are neonates

and note that the anogenital distance is larger in the male than in the female neonates, the penis and vulva cannot be easily differentiated and so are referred to as a genital papilla. The bottom two animals are adults; genitalia are differentiated.

• Also, nipples become evident in females at about 10 days of age.

Sexing mice - The distance between the anal and

genital orifices is greater in the male (left)

compared to the female (right).

Female Male

Normal Rat

Normal Mouse

Sick Mouse

Hunched posture Hunched posture

Signs of Pain and Distress in

Rodents • Decreased activity

• Unkempt fur (not grooming)

• Pilo – erection

• Hunched posture

• Rapid shallow Breathing

• “ Red tears “ albino rats”

• Squinting of eyes

• Vocalization

• Feed and/or water refusal

• Weight loss

Alopecia Hair loss

• Due to excessive grooming

• Metabolic dysfunctions

• External parasites and Nutritional disorders

Fight Wounds

Fighting is usually seen in males. The wounds are often seen on the tail, backs and genital area.

Dystocia = difficult birth

• This is when a female has difficulty giving birth.

• Signs might include vaginal discharge, dehydration, and lethargy.

• Normal mice give birth only at night – if they are in labor during day , something is wrong.

• There may also be dead pups in the cage.

• Normal birth times = 1 – 3.5 hours for a litter of 11 pups

Head Tilt

Minimizing Pain and Distress

WHEREVER POSSIBLE, PAIN/DISTRESS SHOULD BE ELIMINATED Causes of Pain and Distress in Mice • Spontaneous and experimentally-induced disease or

injury.

Now let’s find out what you think.

• What is your opinion about using animals as models in research?

• You are going to do an assignment in which you will express your views!

ROUTES OF DRUG ADMINISTRATION to laboratory animals

Medication : A substance administered for the diagnosis, cure, treatment, relief or prevention of disease.

Principles in Administering Medications : Principles in Administering Medications Observe the “7 Rights” of drug administration

1. Right drug

2. Right Dose

3. Right time

4. Right patient

5. Right Route

6. Right Approach

7. Right Recording

• The possible routes of drug entry into the body may be divided into three classes:

▫Enteral

▫Parenteral

▫Topical

I. ENTERAL ROUTE

1. Sublingual: under the tongue

2. Oral administration (P.O.)

3. Rectal or vaginal

II. PARENTERAL ROUTE: administration of medications by needle

1. Intravenous (I.V.): into vein Fastest

2. Subcutaneous (S.C.): in the subcutaneous tissue Slowest

3. Intramuscular (I.M.) Medium

4. Intraperitoneal (I.P.) : into the peritoneum (body cavity)

5. Intraarterial: direct inject into artery

6. Intradermal: under the epidermis or into dermis

7. Intraosseous: into the bone

III. PULMONARY ROUTES: Inhalation into lungs

IV. TOPICAL

I. Nasal

II. Skin

III. Eye

Enteral Routes • Enteral - drug placed directly in the GI tract:

▫ Sublingual - placed under the tongue

▫ Oral - swallowing (p.o., per os)

▫ Rectal or vaginal - Absorption through the rectum or vagina

Some drugs are taken as smaller tablets which are held in the mouth or under the tongue.

• Advantages ▫ Rapid absorption ▫ Drug stability ▫ Avoid first-pass effect

• Disadvantages

▫ Inconvenient ▫ Small doses ▫ Unpleasant taste of some drugs

ORAL ADMINISTRATION

A catheter or hypodermic needle • 15-16 for rat & guinea pig • 18-20 for mouse 1. Advantage

• Convenient - can be self- administered, pain free, easy to take • Absorption - takes place along the whole length of the GI tract • Cheap - compared to most other parenteral routes, does not

need sterilization • Safe

2. Disadvantage

• Drugs irritant to stomach: nausea and vomiting • Leads to food drug interaction • First-pass effect - drugs absorbed orally are initially

transported to the liver via the portal vein, Drugs extensively metabolize by the liver, only part of the drug may be absorbed

First-pass Effect

• The first-pass effect is the term used for the hepatic metabolism of a pharmacological agent when it is absorbed from the gut and delivered to the liver via the portal circulation. The greater the first-pass effect, the less the agent will reach the systemic circulation when the agent is administered orally

1. Unconscious patients and children

2. If patient is nauseous or vomiting

3. Easy to terminate exposure

4. Absorption may be variable

5. Good for drugs affecting the bowel such as

laxatives

Rectal

INTRAVENOUS ADMINISTRATION Placing a drug directly into the blood stream Needle No. 27 Maximum volume should not exceed 0.4 ml

1. Advantage • Rapid action: precise, accurate and almost immediate

onset of action • Valuable for emergency use • 100% bioavailability: Absorption phase is bypassed • Irritant drug can be given only I.V. • large quantities can be given, fairly pain free

2. Disadvantage • Not suitable for oily solutions & insoluble substances • Lack of sterility may cause viral hepatitis & AIDS • Increase the risk of adverse effects • Must inject slowly in order to minimize the effects of

drug on the heart

SUBCUTANEOUS ADMINISTRATION

1. Advantage • It provides sustain effects because of slow

absorption • Addition of vasoconstrictor decreases further the

rate of absorption from the site of injection • It is suitable for insoluble drugs such as pellets and

suspension

2. Disadvantage • Can not inject large volume • Can not inject irritant drug • Repeated injection leads to necrosis (atrophy of

skin)

INTRAMUSCULAR ADMINISTRATION

Maximum amount should not exceed 0.4 ml for mouse and 0.5 ml for rats & guinea pigs

1. Advantage • Suitable for oily vehicle and irritant drug • The rate of absorption is very high because of high

blood flow in the muscle

2. Disadvantage • It is not recommended in patient taking Anti-

coagulant • Increase Creatine Phosphokinase

• The needle is pushed firmly through the abdomen in a region away from liver, kidney and spleen.

• Maximum volume:

▫ Mouse: 1.0 ml

▫ Rat & guinea pig: 2.0 ml

▫ Cat & Rabbit: 5.0 ml

1. Gaseous and volatile agents and aerosols

2. Rapid onset of action due to rapid access to

circulation

a. Large surface area

b. Thin membranes separates alveoli from

circulation

c. High blood flow

Inhalation

Topical Mucosal membranes (eye drops, antiseptic, sunscreen,

nasal, etc.)

Skin

a. Dermal - rubbing in of oil or ointment (local action)

b. Transdermal - absorption of drug through skin (systemic

action)

i. stable blood levels

ii. no first pass metabolism

THANQ…

Introduction

to

Neuro-Pharmacology

Nervous System

which consists of

is divided into

that make up

which is divided into

The Nervous

System

Sensory nerves

(Afferent Nerves) Motor nerves

(Efferent Nerves)

Autonomic nervous system

Somatic nervous system

Central nervous system

Peripheral nervous system

Sympathetic

nervous system

Parasympathetic

nervous system

Peripheral Nervous System

Peripheral Nervous System

Nervous structures outside the brain and spinal cord NERVES that connect the central nervous system to

the rest of the body Nerves allow the CNS to receive information and

take action 1.Sensory (afferent) Division – transmits

impulses from sense organs to CNS 2.Motor (efferent) Division – impulses from

CNS to muscles or glands Two Parts:

Somatic Nervous System

Autonomic Nervous System

Afferent • It is known as sensory or receptor

neurons which carry nerve impulses from receptors or sense organs toward the central nervous system.

• It is known as motor or effector neurons which carry nerve impulses away from the central nervous system to effectors such as muscles or glands

The Peripheral Nervous System

Efferent nervous system

Somatic nervous system

(voluntary)

Skeletal muscle

Autonomic nervous system

(involuntary)

Heart, blood vessels,

glands, other visceral

organs, smooth muscle

1. Sympathetic NS (fight or flight) – Catabolic (expend energy) – Mass activation prepares for intense activity.

• Heart rate (HR) increases. • Bronchioles dilate. • Blood [glucose] increases.

2- Parasympathetic NS (rest and digest) – Maintain homeostasis – Normally not activated as a whole, stimulation of separate

parasympathetic nerves. – Relaxing effects:

• Decreases HR. • Dilates visceral blood vessels. • Increases digestive activity.

The Autonomic Nervous System

Effects of Sympathetic Activation

Generalized response in crises

Increased alertness/energy

Increased cardiovascular activity

Increased respiratory activity

Increased muscle tone

Effects of Parasympathetic Activation

Relaxation

Food processing

Energy absorption

Brief effects at specific sites

Neurotransmitter:

A chemical that transmits signals from one neuron to another

or from a neuron to an effector cell.

Electrical

Stimulation

(impulse)

Chemical

(neurotransmitter)

Chemical

(intracellular

messengers)

Electrical

(membrane

ion channels)

Physiological

functions

Neurotransmitter-based classification 1- Cholinergic, 2- Adrenergic, and 3- Dopaminergic

1- Cholinergic transmitter

• It means related to the neurotransmitter Acetylcholine.

• The parasympathetic nervous system is entirely cholinergic. Neuromuscular junctions, preganglionic neurons of the sympathetic nervous system, and the sweat glands

2- Adrenergic

•It means "having to do with adrenaline (epinephrine) and/or noradrenaline (norepinephrine)".

3- Dopaminergic

• It means related to the neurotransmitter dopamine. For example, certain proteins such as the dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2)

../My Documents/Downloads/Activation of a Neuron.flv

Definition of Agonist and Antagonist

Agonist: A structural analog that is capable of stimulating a biological response. Antagonist: A receptor-specific blocker (e.g., enzyme inhibitor) or a physiologic agent (e.g., hormone), that prevents the action of another molecule.

Classes of cholinergic stimulants

Direct-acting

Receptor agonists

Choline esters ACETYLCHOLINE

BETHANECOL Alkaloids PILOCARPINE

Cholinesterase inhibitors

Carbamates PHYSOSTIGMINE

NEOSTIGMINE

PYRIDOSTIGMINE

EDROPHONIUM

Phosphates ISOFLUROPHATE

Antidote

PRALIDOXIMINE

Indirect-acting

Acetylcholine

• Preganglionic synapses of both sympathetic and

parasympathetic ganglia

• Parasympathetic postganglionic neuroeffector junctions

• All somatic motor end-plates on skeletal muscle

NANC (non-noradrenergic,

non-cholinergic transmitter)

Muscarinic Actions

• Similar to those of parasympathetic stimulation

• •(M1): CNS, PNS, gastric parietal cells

• •(M2): conducting tissue

• •(M3): exocrine glands; smooth muscle

Nicotinic Actions

• Similar to those induced by nicotine

• Stimulation of all autonomic ganglia (Nn)

• Stimulation of voluntary muscles (Nm)

• Secretion of epinephrine from the adrenal medulla (Nn)

What is a synapse?

• A synapse is the junction between 2 neurones.

• There is a very narrow gap of about 20nm between neurones called the synaptic cleft.

• An action potential cannot cross the synaptic cleft, so nerve impulses are carried by chemicals called neurotransmitters.

A Synapse

• Pre-synaptic neurone = neurone sending impulse

• Post-synaptic neurone = neurone receiving impulse

Neurotransmitter

• Neurotransmitter is made by the pre-synaptic neurone and is stored in synaptic vessels at the end of the axon.

• The membrane of the post-synaptic neurone has chemical-gated ion channels called neuroreceptors. These have specific binding sites for neurotransmitters.

Cholinergic Synapses

Acetylcholine is a common transmitter.

Synapses that have acetylcholine transmitter are called cholinergic synapses.

Some neurones form more than 1 synapse.

• This is an electron micrograph of synapses between nerve fibres and a neurone cell body.

An action potential arrives at presynaptic membrane. Voltage gated calcium channels in the presynaptic membrane open, calcium ions enter the presynaptic neurone.

What happens at a cholinergic synapse?

Stage 1

• Calcium ions cause synaptic vesicles to fuse with the presynaptic membrane, releasing acetylcholine into the synaptic cleft.

What happens at a cholinergic synapse?

Stage 3

• Acetylcholine diffuses cross the synaptic cleft and binds to specific neuroreceptor sites in the post synaptic membrane.

What happens at a cholinergic synapse?

Stage 4

• Sodium channels open. Sodium ions diffuse into the postsynaptic membrane causing depolarisation, which may initiate an action potential.

• Acetylcholinesterase breaks down acetylcholine. The products diffuse back into the presynaptic neurone where acetycholine is resynthesised using ATP from the mitochondria.

What happens at a cholinergic synapse?

Stage 5 & 6

Neuromuscular Junctions

• Same stages as cholinergic synapses, but in this case the postsynaptic membrane is the muscle fibre membrane, (Sarcolemma). Depolarisation of the sarcolemma leads to contraction of muscle fibre.

Drugs

• Drugs which have molecules of similar shape to transmitter substances can affect protein receptors in postsynaptic membranes.

• Drugs that stimulate a nervous system are called AGONISTS

• Drugs that inhibit a nervous system are called ANTAGONISTS.

Summary

• A synapse is the point where 2 nerve cells meet. Tiny gap = synaptic cleft.

• Chemical transmitter released from presynaptic neurone diffuses across synaptic cleft & fits into receptors on postsynaptic membrane. May cause postsynaptic neurone to depolarise & set up action potential.

• Neuromuscular junction = motor neurone connects with muscle fibre – similar to a synapse.

• Many drugs affect synapses.