Synapses Drugs and Behavior COMMUNICATION BETWEEN TWO NEURONS The way information is transmitted along an axon on a neuron is different from the way information is transmitted between neurons In almost every instance chemicals are transmitted between neurons Communication between two neurons depends on the production of chemicals called neurotransmitters by neurons Some are made in the axon and some in the soma Action potential travels down the axon once it reaches the terminal bulbs calcium dependent gates open Calcium enters the cell and the neurotransmitter leaves Neurotransmitter leaves the pre synaptic neuron travels across the synaptic cleft and binds to the post synaptic receptor Once the neurotransmitter completes its task it s either converted to something inactive or reuptaken by the pre synaptic neuron At any point the post synaptic neuron releases other neurotransmitters that tell the pre synaptic neuron to stop transmitting There are lots of chemicals in the body that can be used as neurotransmitters As a result the definition of neurotransmitter has become fuzzy over the years There are many different classes of neurotransmitters Amino acids are within the NH2 group There are certain gases that also serve as neurotransmitters NO We make our own neurotransmitters from our diet Neurotransmitters made in the soma have to travel down the axon to be released If this is the case they can be exhausted pretty quickly Most neurotransmitters are stored in vesicles in the axon terminal tiny spherical packets NO is never stored used immediately when produced Most neurons release more than one kind of neurotransmitter Most neurons can also receive most kinds of neurotransmitters Dopamine is a neurotransmitter There are multiple receptors that can bind the dopamine Some neurotransmitters when they bind cause an ionotropic effect a gate opens and things happen quickly Ionotropic effects can be seen at synapses when information is changing rapidly vision is an example Ionotropic effects are needed when things change rapidly Metabotropic effects are slower they involve second messenger systems Glutamate is the most common neurotransmitter in our DNA an excitatory transmitter It typically causes ionotropic effect Creates EPSP Another neurotransmitter is called GABA an inhibitory neurotransmitter causes IPSP Most of GABA causes ionotropic Just as much information is transmitted by inhibition as excitation Neuromodulator effect If neurotransmitters cause this they aren t acting on their own They commit modulator response of other neurotransmitters They re not always released from axons they can be released from anywhere on the neuron Are not typically released in large amounts Tend to modulate the effects of neurotransmitters that are typically released Some neurons have auto receptors Neurons with auto receptors have receptors for the same neurotransmitter they release If neurons release a lot some neurotransmitters feed back to the auto receptor to let the neuron know they ve released enough and to stop It s one way that a neuron knows to stop transmitting Retrograde messengers are chemicals that are released by the post synaptic neuron that feed back to the pre synaptic neuron Once the neurotransmitter does its purpose several things can happen It can be broken down at the receptor site it s broken down into acentane and coline via the enzyme acetocolinehestahime Other neurotransmitters like serotonin go through reuptake it detaches from the receptor and goes to the pre synaptic neuron They re helped by transporters to get back Some of these chemicals can be turned into inactive substances Most neurons have a spontaneous firing rate All these neurotransmitters cause the spontaneous firing rate The net effect of IPSP and EPSP tells a neuron whether to fire or not if all is released is GABA then the neuron won t fire Most drugs work by altering the ionic transmission along an axon they work by effecting neurotransmission some way or the other Some can effect neurotransmitter production storage or release Some can also effect the post synaptic receptor Drug use can be good or bad Soda 7Up used to contain lithium Coca Cola used to contain cocaine Indigenous substances are things our own body makes like insulin Endogenous are things made in a lab like heroin Study of drugs and their effects on our behavior is psychopharmacology Any drugs used in research are very closely monitored by the DEA Psychopharmacologists are used by pharmacologists one has to determine whether a newly developed drug is reinforcing You don t want a drug to be reinforcing because that s addicting Animals lever pressing is one way to test for the a drug s reinforcing tendencies Conditioned placed preference CPP is another way One needs a box in a square that s divided into three different sections The idea is that the sections in the box look and feel different to a rat In the middle is the smaller chamber that has two doors on either side that are closed When testing check to see which chamber the animal goes into when given the choice the chamber the drug was paired with or the other It s not at all uncommon for us to discover an endogenous drug before we discover what we make indigenously that binds to the same receptors as the endogenous drug Like morphine and opiates we make our own opiates Drugs that mimic or enhance the effects of a neurotransmitter are called agonists Drugs that block the effects of neurotransmitters are called antagonists Anytime we talk about a drug and its effects we need to talk about a drug s affinity which is the strength of attachment to a receptor Indigenous substances typically have very high affinities to receptors And the drug or neurotransmitter with a higher affinity can displace a drug or neurotransmitter with a lower affinity Also need to think about efficacy Efficacy is the ability of a drug to stimulate a receptor once it s bound So one can have very high affinity and low efficacy and vice versa When we re talking about a drug we re talking about receptor mediated effects Receptor mediated side effects can also be seen Any particular drug has an objective but it will most likely have side effects which are due to the drug s effects at other receptors The more specific a drug the better it is because it only works on the intended receptor Anytime you talk about any drug reaction you have to say usually or typically because there are ALWAYS going to be exceptions