TIPS -June 1987 IVol. 81

Altema tive methods to teaching practical pharmacology

‘Master-slave” demonstrations

I was interested to read the lead- ing article by MacDonald and Saano in the March issue of Tips’. I am sure that most educators involved in the teaching of pharma- cology to undergraduates in uni- versities have come to similar con- clusions about the effectiveness of alternative methods in teaching practical pharmacology.

At Heriot-Watt University De- partment of Pharmacy, we have for a number of years reduced the practical element of our teaching because of our concern regarding animal conservation and because of financial exigencies. However, our approach has been somewhat different and perhaps combines the best of both worlds regarding demonstrating known facts on live tissue or animals, while reducing the wastage of animal life. Some of our practical classes now take the form of ‘master-slave’ demon- strations, in our case using this facility on Washington recorders. This means that we set up only one real, live preparation, and have all student recorders ‘hooked up’ to this ‘master’ recorder. The practi- cal class then takes on the form of a ‘master class’ cum tutorial, with the lecturer or demonstrator actu- ally performing the experiment ‘live’, while each student watches and keeps a permanent record of a genuine experiment at which he or she was present.

The advantages of such a method are manifold; e.g. the lec- turer or demonstrator does all the calculations, additions of drug so!utions, i.SUY ,hrwx x!w~bg the &axes of mistaken lethal con- centrations or of ineffective sub- threshold concentrations. Stu- dents can be involved in a discus- sion throughout of the possible outcome of each drug addition. The percentage success of the whole ex- periment increases quite dramati- callyinexperiencedhands,andany unexpected results can be (hope- fully) explained at the time of observation. Also students can have the opportunity of exam-

ination of the real preparation at some time during or after the demonstration, so that, although they may not gain ‘hands on’ experience, they at least may see the preparation at close quarters, and in the flesh, which is infini- tely superior to the videotaped version.

This technique lends itself ideally to those experiments which are expensive in animal terms such as all cardiac prepara- tions, (e.g. Langendorff hearts, isolated atria), isolated diaphragm, chick biventer preparations of skeletal muscle, pithed rat blood pressure, etc, etc. The only animal experiments which our students do

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gain ‘hands on’ expetience of are those such as guinea-pig ileum, Finkelman preparatioila, etc, where the sacrifice of one an&nlG! will provide sufficient tissue for a class of 30-40 students (working in pairs).

We also use computer simula- tions* of many of the experiments which have been demonstrated by the ‘master-slave’ technique, so that students can at a later date indulge in some revision without cost to animai life, and with a minimum of academic or technical staff supervision. These computer simulations are also linked to standard chart recorders, and give a very life-like reproduction of the ‘real thing’.

NEIL SCOTT Deparhent of Pkammy, Heriot-Watt thi- ugity, 79 Grassmarkef, Edinburgh &HI 2tiJ.

References 1 MacDonald, E. and Saano. V. (1987)

Twnds Pkamacol. Sci. 8,77-78 2 French, A. M. (1983) Br. I. Pkermncol. 80,

Prvc. Suppl. 592P

Evidence &presented to support an alternative cksi?kation

Classification and function of CCK receptors We noted with some concern the recent centrefold ‘Peptides, recep- tors, antagonists’ in Tips by Regoli’ in which a classification and biological functions were pro- posed for CCK receptors. Regoli’ proposes that CCKI receptors are defined by binding in rat pan- creas and are seiectiveiy antagon- ized by the potent CCK antagonist _ _. _. L-364718 (Ss(-)N-(2,3-dihydro-i- methyl-2-oxo-5-phenyl-lH-1,4- benzodiazepin - 3 - yl) - lH- indole - 2-carboxamide)*. CCKz receptors are proposed as being defined by binding in guinea-pig brain rbr which no selective anta

B onist has

been described to date . Further, Regoli’ suggests that CCKI recep- to.rs sEAiuulate pancreatic or bile secm’rion and gall bladder tonus and inhibit gastric emptying. In contrast, CCK2 receptors are Jaimed to inhibit appetite, gastric motility and secretion and to mediate ‘other central effects of CCK”. We dispute Regoli’s classi- fication scheme for CCK receptors for two principal reasons. First, we believe that this classification

is inappropriate and likely to cause confusion in the literature. Secomd, the biological functions suggested for the different recep- tor types are at variance with published data and results in the press.

We believe that the nomen- ciature of CCY,, and CCK2 is inappropriate to describe the so- ded ‘peripherai’ and “brain’ type

CCK receptors respectively In- deed, Moran and colleagues have shown that ‘peripheral’ type CCK receptors, occur not only in peri- pheral tissue but also in certain discrete regions of the brain in- cluding area postrema, nucleus of the solitary tract and inter- peduncular nucleus. Those recep- tors have been ternled CCK-A receptors whereas other brain binding sites have been termed CCK-B (‘brain’ type) receptors3. Recent experiments in our labora- tory have confirmed the findings of Moran et al.” and have clearly shown (using autoradiography) that binding to CCK-A (‘peri- pheral’ type) receptors in rat brain

Q 1987, Ekvicr Publlcnlions, Cambridge 0165 - 6147/67/SOZ.M)